Understanding Coordinate Systems and Projections for ArcGIS

welcome everyone thanks so much for joining us today for the Society for conservation GIS webinar series I'm Tasha Commandant a senior scientists at CBI and I'll be hosting and facilitating our presentation today just a few points we're recording the session you'll be able to find it on this link here I'll show you that again you are in listen-only mode so we encourage questions so please type those into the question field or comments and there is a raised hand icon that you can click on to indicate that you want to unmute your line so just briefly I'm a board member for SC GIS we have a long time active member as our presenter today John Schaefer so we want to just let you all know for those who aren't familiar that there's a couple ways you can get involved this is a volunteer run society with a lot of active participants from our listserv or social media so the way you can you know contribute is following us becoming a member if you're not or renewing if you haven't and then on our website there's a lot of information about our annual conference as well so I encourage you to get involved or asking questions if you have any any of those so just quickly our webinar will be posted here afterwards I'll make a recording so for example here's our last one we had with Joseph Persky hear featured on top as well as the upcoming schedule of other webinars you might be interested in and so I'm really pleased to be able to turn the screen over here to John Shaffer he's gonna lead us through a hour and a half long presentation that's the time allotted a little extra time here so John go ahead and show your screen I think I am showing my screens every wouldn't see it I can see it it looks great go right ahead okay so Tasha will have this presentation up on her website and also I've got a link to where you can find on my website along with some others but if you don't know me I have been involved with segs since about 2000 2001 I've been the primary instructor for the Scholars Program since 2009 been working a lot with GIS since 92 and I've focused on practical aspects how to get the job done and this presentation is based on all the head-banging that I did to understand coordinate systems when I was first learning about them so hopefully it will be useful to all of you and like Tasha said questions are welcome but we'll hold them till the end kind of consolidate all of the questions so let's get started so presentation objectives so understand basic concepts on coordinate systems will go through terminology what all those words really mean geodesy shape of the earth geographic coordinate systems datums map projections projected coordinate systems probably most important working with projections in ArcGIS so kind of your basics there so on this terminology there's a lot of terms and I found I don't need to know all of them but I'm going to go through them quickly and then concentrate on the important ones so coordinate system a reference framework consisting of a set of points lines and our surfaces and a set of rules used to define the position of points in space geographic coordinate system that's a reference system that uses latitude and longitude to define locations of points I think it's pretty obvious important part here is it can includes a datum primary and angular unit of measurement so we'll come back to that in a minute projected coordinate system reference system used to locate X Y and C positions of point line and area features in two or three mentions important part about this a projected coordinate system is defined by a geographic coordinate system so it's not really stand-alone map projection any parameters needed by the map projection in a linear unit of measurement rather than a angular unit and again we'll go over this again more plane our coordinate system just basically saying we're on a flat two-dimensional plane okay now what's kind of important about here and any projected coordinate system is that the units are constant Cartesian coordinate systems so French mathematician Rene Descartes okay so this is pretty much two dimensional plane our coordinate system you have a horizontal access measured along the x vertical distance measured along the y axis up and down important part about this and we'll come back to it later is that the 0 0 where the X and the y axis meet is in the center and that as you go to the right on the x axis values go up as you go to the left values are negative same thing for the Y's you go north Y is positive you go south Y is negative and so that means in this upper white right quadrant quadrant one that's the only place values are positive for both x and y and you'll see with where that comes into play later on datum so a couple terms for datum the reference specifications of a measurement system so it's kind of like the underlying rules for your coordinate system okay usually a system of coordinate positions on a surface or heights above or below a surface so that'd be our vertical datum geodetic datum little more precise datum that is a basis for calculating positions on the Earth's surface or heights above or below the earth's surface and datums are based on specific ellipsoids and sometimes actually often have the same name as the ellipsoid geocentric datum local datum couple more important terms so geocentric datum is a datum where it's based on ellipsoid that has its origin at the Earth's center of mass examples are a world geodetic system 1984 this is what we see is widgets wgs84 North American datum 1983 and this number of other examples and these are more compatible with GPS because you think about it GPS you have two satellites up in the sky they're pointing towards the center of the earth then you also have local datum so this is a horizontal geodetic datum based on an ellipsoid that has its origin on the surface of the earth such as North American datum 1927 so in the littlest illustration here okay this kind of black line little squiggly here that's the Earth's surface the red dashed line that's our local datum and it's like I've taken the ellipsoid for the datum and just pushed it up to one part of the earth and I did that because that's the part of the earth I'm concerned about and so that's going to make it a little more accurate there so that's why yes I'm like North American datum and you wouldn't try to use a North American datum say in Mongolia it wouldn't make sense and then the blue line is our earth centered or our geocentric datum okay now ellipsoid or the word spheroid actually when I first started working with this it took a took a while before I realized ellipsoid spheroid or really the same same term a three dimensional closed geometric shape all playing our sections of which are ellipses or circles yada yada yada basically an ellipsoid approximates the shape of the earth and former size and the key thing about an ellipsoid is that it's not completely circular it's a little flatter at the top bulges out a little bit in the middle and so this is what we use as a reference surface is a particular lip side or datum okay and over down on the bottom right there's a list of different ellipsoids different datums essentially and the figures over the right are just basically kinda measurements of how wide it might be at the middle and how flat it might be at the top so you know we have hundreds of different models of the globe or different datums transformation and geographic transformation transformation process of converting the coordinates of a map or an image from one system to another usually by shifting rotating scaling etc Geographic transformation this is much more important for us it's the systematic conversion of the latitude longitude values for a set of points from one geographic coordinate system or datum to equivalent values in another geographic coordinate system so when you're switching datums you're doing a geographic transformation if you're working within one datum then you can be basically just kind of doing a little transformation but that Geographic transformation that we sometimes call the datum shifts really important if you don't pay attention to this and we'll show this in demonstrations then your data is going to be off like in the little illustration here projection or map projection a method by which the curved surface of the IRS's is portrayed on a flat surface so basically we have some type of mathematical system routine that people much smarter than me have developed that says this is how we move these lines of latitude longitude on to this particular flat plane okay so those are all the terminology you will see and that I had to go and kind of figure out and decide does this make sense or how does it all fit but there's really just five terms you need to understand geographic coordinate system the earth is a spheroid with location latitude longitude with unison degrees projected coordinate system the earth or parts of it flat with location and constant units datum a large scale reference grid based on a spheroidal model of the earth projection that's the method of converting locations from one coordinate system to another in GIS we tend to be pretty sloppy so sometimes we'll say projections when we really mean coordinate system so I'm trying to be a little more explicit here so we have geographic coordinate system projected coordinate system but when I say projection is the method for from changing from one coordinate system to another and then geographic transformation that's the method to convert locations from one datum to another datum as part of a projection ok now coordinate systems and datums geographic and projected coordinate systems are linked to datums and we've mentioned this before datums or different ways of measuring the shape of the earth and impact both geographic coordinate systems using latitude longitude and projected coordinate systems so I've had people come up to me like I'm working on a wildland fire and dozer driver comes in he's got some points and that lat/long says here I've got some points for we were just dissing work and then I asked him what datum they're in and is all confused and a lot of people don't realize that any latitude longitude measurements are tied to a datum so I can take latitude longitude and dub Geoff's 84 which is my you know settings for my GPS or maybe I'm working off old map and the latitude longitude might be in nad27 you know North American datum in 1927 so even latitude longitude are tied to Pacific datums probably more technically tied to a particular ellipsoid okay so just think of datums as a set of established reference points to which a particular coordinate system is tied or registered datums and geographic coordinate systems are often the same many cases a data may be named the same as a GCS geographic coordinate system and in ArcGIS almost anytime you see the phrase geographic coordinate system think datum okay so that's what it's really talking about now common datums used in the US so I'm going to use a lot of us examples but please realize anywhere you are in the world you're going to have a similar system okay and I'll give you a couple examples as we go so in the u.s. we have North American datum 1927 based on the Clarke ellipsoid 1866 and North American datum 1983 based on this grsat ellipsoid and high accuracy reference networks Harn okay that uses GPS satellites for control a little bit better than just a grsat world geodetic system 1984 wgs84 difference between a 27 and nad 83 in the western US where I worked it's about a hundred meters so I'm not paying attention to which datum I'm using I can be a hundred meters off if I'm working tree nad83 and horn is about 16 feet if I happen to work in between India 1948 and wgs84 this was something used in Cambodia it's a thousand meters so really important to pay attention to this and in your own region of the world you might just need to know two or three datums now why do I care about the fact that nad27 is based on Clarke ellipsoid of 1866 well I got some data from u.s. Forest Service long time ago and they called out a datum of Clarke ellipsoid we there's no datum called Clarke ellipsoid listed under any of the ESRI documentation but the fact that I knew nad27 was based on Clarke ellipsoid meant that I could go in change the definition of the coordinate system to nad27 instead of Clarke ellipsoid and then aren't yes understood what was going on and everything happened so you don't need to learn all the datums but the two or three datum sinews in your area if you just kind of look up a little bit of the information about them that can sometimes help you solve problems when you're having issues with data alignment things like that geodesy study of the shape of the earth initially thought to be flat well I'm not too sure about that later thought to be a sphere so perfectly round in all directions but French geographers in 1730s proved that the earth is an ellipsoid okay so basically that means bulges out a little bit in the middle a little bit flatter at the top and so we've ganna listen to some of the common ellipsoids but all of the ellipsoids are based are different just different measurements of the flattening at the poles okay so just slightly different shape of the earth then there's something called the geoid you probably might only run it the only place I run into the geoid with any practical implications is working with GPS and vertical data so the geoid and you'd have to be a physicist understand all of this I think this is a hypothetical figure of the earth that represent the surface as being at mean sea level but still influenced by gravitational pull density of Earth's materials and hydrostatic forces yeah whatever actually what I like about this slide is the fact that it can show us the Earth's surface this nice smooth ellipsoid and the GI that you know kind of wanders a little bit so mostly I like it to kind of show you how the ellipsoid might work and relationship to the Earth's surface but there is one place that you need to pay attention to this it affects how elevation is measured and also can affect the location of a point on earth so if you weren't between different coordinate systems you may need to know how elevation is being measured you have choice of height above ellipsoid height above geoid where I live in Bend Oregon it's about a 64 foot difference and again the only place I really ran into an issue with this is comparing some GPS data to an old paper USGS map and I needed to pay attention to the fact that one right now I don't remember which one the map paper map might have been using height above ellipsoid and the GPS was using height above geoid so it's just one more thing that you know you want to pay attention to probably not critical for most work that you might be doing now measuring the earth and 3d latitude longitude so pretty straightforward latitude longitude measures and degrees so many degrees around so many degrees up and down but not in distance the length of a group of a degree changes over different parts of the earth so even along a Meridian going up and down you know it changes along our parallels here like the equator a degree at the equator is really large a degree up here you know where I live 45 degrees north is really small but the fact is they're not constant so not something you want to use measuring distance or area so location north and south is measured from the equator and you can see the equator over here location east to west measure from the prime meridian as a GIS person I had to do this I was in Kenya on Wednesday and I had a chance to be at the equator the next Tuesday I was in London so of course I had to go to the Prime Meridian and then on another trip I had to go to Fiji and you know be on the International Dateline so those are the key lines that basically what we use as reference for a latitude/longitude now distortion impossible to flatten a round object without distortion okay so this is where I might take an orange peel if you could all see me and I you know break the peel and try and squish it flat of course it would all break up okay so I think that's pretty obvious I can't take this round thing and make it flat now when you work with projections you try to preserve a one or more of the following properties area sometimes called equivalents shape sometimes called con formality direction as modality or distance and so when choosing a projection consider the type of measurement what type of measurement is important so a good example is you know if I want to take my sailboat from the UC conference in San Francisco and I want to go over to Y I better have a map where the projection is based on direction if I want to measure all my bike rides I better do distance rather than say area shape okay now for most of us we really don't have a choice in choosing a projection as a practical matter the projection you use is based on the materials you are working with the data you're working with in general but remember that you do have these different choices depending on what's more important area shape direction distance so a little cartoon here going from 3d to flat Maps transformation on the round earth onto a flat surface using latitude longitude as reference and you know you didn't tell me it's going to be an abstract and that it's so here's a few examples so the world has seen from space and 3d this actually comes from our view 2.0 I couldn't find the equivalent in ArcGIS for this view this projection the world projected onto a flat surface so this is where Russia or Greenland look really really huge kind of out of proportion the world is seen from an Oregon perspective so I work usually with Oregon State playing South NAT 83 and this coordinate system makes Oregon look correct and tends to kind of screw with the rest of the world so you know Brazil Argentina get a little bit warped out here if I'm in Mexico this is what the world would look like if I'm in Colombia this is what it would look like in Indonesia and a little advertisement it looks like I'll be partnering with SDGs Indonesia to do a class in Bali this October so I'll have to make use of this coordinate system Kenny yeah this is what the world looks like from Kenya France India I kind of like this one and like the whole world just kind of swoops up around India and then South Africa so the point of this the reason we have thousands and thousands and thousands of coordinate systems is the fact that you design a coordinate system for your area of interest you make it as small as possible so the world looks correct where you are okay and because of distortion the rest of the world's not going to look so good but that's the reason we have these thousands and thousands and thousands of coordinate systems now the way these are created it's done by transferring points on the earth onto a flat surface so think about this as having a light in the middle of the earth it shines out through the Earth's surface on to a projection surface it's kind of like we lay a piece of paper against the earth we'll have a few slides that show you three main types plane are so projection surface laid flat again 0th conic this is a cone kind of like a dunce cap placed on or through the surface of the earth excuse me cylindrical projection surface wrapped around the earth and where the projection surface touches the earth is the standard line so here's a few examples so plane are primarily used for North Pole South Pole okay so where that piece of paper hits right here in the center of the pole center of the North of the earth okay everything's cool as we move away you know we're going to increase the distortion conic this is where we take a cone and kind of drop it over the globe and this is good for areas that go primarily east-west because our standard line where it meets the globe is running east-west cylindrical we just take a cylinder and put it around the globe but with a cylindrical usually what we do is this is we do what we call transverse mercator where we take that cylinder turn it 90 degrees sideways and so then what we have is our true line or standard line then goes north-south so everything is good along this line the further away we get from that line you know the more projection we have okay so when you heard that we're a transverse Mercator it's just a big word for taking the cylinder and flipping it sideways so it's basically going north-south oriented to the globe and then there's the famous origami projection well actually this is a joke there's no origami projection but the concept here is anyway you can take a piece of paper fold it around the globe and then unfold it flat can be used as a you know projection method okay so there's quite a lot of these different types but mostly we stick with conic and transverse Mercator those are the most common ones and then again the polar projection of plane our projections developing a cylindrical surface so this is basically I've taken that conceptual piece of paper wrapped around the globe in whatever way I can wrap it around the globe cut it and lay it flat so that's what we kind of call developing your projection so that's the concept behind this now here's an example of projection distortion this a say conic projection cuts through the Earth's surface at two parallels this is widely exaggerated in true practice it would really slice through just a little small part of the globe but just to kind of see the concept of what's happening so as this projection surface that cone slices through right here at this point everything is good right here at this point where the actual Earth and the projection plane meet that's good so there's two standard lines in this case here and we can see a B on the earth is a little bit longer than a B on the projection so that's our distortion there if we come down to CD CD on the earth is pretty small but CD on the projection quite large okay that's our example of our project our distortion but again I want to emphasize the fact that the reason we have so many different coordinate systems is that we work in a small enough area that we minimize the distortion when we're we're using these coordinate systems now projected coordinate systems plotting location on a flat map so now that we've got this established we've got the reference points they projected onto a flat surface then we can establish a coordinate system that provides a common reference so we mentioned this before we have our x axis going east-west our Y axis going from North the South where they meet and usually we Center this point we put this point where they meet in the center of our area of interest and this goes back to that Cartesian coordinate if I'm in the upper right quadrant I have positive values and the X positive values and the Y each of these other quadrants I'm going to have at least one negative value and as you can imagine as we start calling out points in reference that 0 0 if we have location with negative values that just can cause problems when we're working with the data we're going to show you how we avoid this issue now coordinate systems have a base line running east-west base line running north-south used to measure distance in two directions from the origin the origin with a given value is zero zeros where the baselines intersects all pretty standard the location many point can be described by listing two coordinates one showing the distance from the east-west baseline and one showing distance from the north-south base line so most CAD mapping systems OCAD just in case computer-aided drafting I actually started teaching AutoCAD and worked with that for several years before I got into GIS but we usually call these XY sometimes of course refer to as easting or northing and one thing you do need to watch for I have gotten data where people have confused the X and y so one really kind of strange thing I don't know why but in most cases when we say XY we say XY in other words we give the horizontal and then the vertical value but we say latitude longitude when we talk about degrees which we're giving the northern value first and then the east-west value second I have to sometimes really remember this and with latitude longitude I think of latitude as like a ladder you know a bunch of rungs going up but just some strange thing like I asked them to quiz you know the equivalent of XY or latitude longitude a couple of people had it backwards and I think it's just because we're used to saying XY with a horizontal value first and then we say lat/long with a vertical value first so I have had a couple situations where people have given me a set of values set columns in Excel and they'll have the terms latitude longitude or XY reverse so you need to watch out for that sometimes now common types of projected coordinate systems for use in the United States and again I'm going to give you a lot of us examples but in each region in the world you'll have your own equivalent sets so for local work a song called state plane coordinate system and we also have the UTM Universal transverse Mercator coordinate system and then for larger things regional continent the word North American albers equal-area we're concerned about area here or North American Lambert conformal conic so with the conformal we're worried about shape the conic and both of these tells me we're using that cone as a way to kind of get our projections started ok we're dropping that cone over the earth now state plane coordinate system one or more zones for each state and I think the general rule for these is you need to make the state plane coordinate system small enough so that your accuracy is 1 to 10,000 in other words I would have to walk two miles before I'm off a foot so that's why we have all of these different you know state plane coordinate systems now usually based on Lambert conic conformal projection for east-west trending States so in this case Oregon we've got to Oregon North Oregon South and that's because Oregon where I live is longer east-west so we take that cone and drop that over the globe and we make the size of the cone hit the earth right where Oregon is okay now you use transverse Mercator we would take that cylinder and turn it sideways for north-south trending states like Idaho Nevada here California is a little bit weird here it is north-south trending but they decided it was May more sense to slice it you know horizontally and use Lambert karna conformal okay usually is a false easting or false northing I'll explain that in a minute units are usually in feet and we'll talk about feet international feet u.s. feet survey feet etc this is an example of how this coordinate system actually lays out kind of on the ground so I'm looking at Oregon State playing South nad83 here's all my specifications okay pull this out from ArcGIS when I'm looking at this it has a central Meridian minus one twenty point five so 120 point five degrees west so that's our central Meridian it has two standard parallels so that's where that cone sliced through the earth in two places so here's our first standard parallel here's our second standard parallel and you can see as we move away from the central Meridian here's our parallel the light brown light blue over here here's the actual line of latitude and we can see we're starting to get some distortion out out here at the edges okay and then the other important part about this is latitude of origin forty one point six six six seven I don't know why they just don't call 41 or some but anyways that's south of our area of interest so this would be our zero zero where the central meridian and the latitude of origin meet the false northing is 0 so we have 0 in our y direction so as i increase my values increase but they're all positive if I left my East value at 0 if I was to move over to the west to the left I would start getting negative numbers so here's how we avoid negative numbers is a false easting in this case 4921 250 feet which puts our zero zero point way over here but it means that all of my values including my X values to the west of my central meridian will be positive values so when you see false easting false northing let me go back to previous slide you see policies thing false northing it's just a trick to move the actual 0 0 off usually to the lower left hand corner of your area of interest where you're working ok and this is a fun thing to do with your coordinate systems is there's a tool on the standard toolbar says go to X Y when you're in a coordinate system click on that tool put in 0 0 and have our just put a mark to see where your 0 0 is you know that's kind of fun to see where you're really starting from and we'll talk about the issue of you know where you're starting from in a couple slides now here's another one this is Nevada state plain East I was helping a consultant do some work here on an environmental impact statement for power line and you can see something very similar we have the actual area covered by the coordinate system and the area of these coordinate systems the lines are really weird it looks like they're really weird that's because they go around County boundaries so in the United States our states are divided into counties as political subdivisions and we don't want to have a county having to use two different coordinate systems we just kind of put the lines around you know County boundaries and stuff here and in this case here this is based on that UTM the transverse mercator ok we'll have our central meridian here at 115 yada yada yada whatever ok down here we have false easting of two hundred thousand so that means I can go over to this part and still be in positive values of my x-direction and a false northing of eight million that sounds really weird look and actually it puts the zero zero way down here somewhere off the almost off Patagonia okay don't know why it's set up like this this is set up by the USGS United States Geological Survey chumps so I'm sure it's done correctly but I'm gonna come back to this false northing value in this and a couple other examples to you so you can see why it's important to take a look at all of these different values in here okay now a little bit about working with a foot so if you're outside the US life is sweet you're working with meters it's very easy if you're in the US or any place uses feet you have a problem there's probably a dozen different types of feet all related to the meter okay so here my US feet is zero point three zero four eight zero zero six oh nine yada yada yada yada meters and if I use international feet zero point three oh four eight zero zero zero zero zero so very minor difference but can have a significant impact so going back to that well one thing I should mention many names but not consistent so not all programs like a GPS program or ArcGIS will necessarily always use the same terminology for foot I found some inconsistencies there so here's why this is important and here's why understanding or being able to read this coordinate system information is important so I mentioned earlier that I was helping a consulting firm that was doing environmental impacts analysis on a powerline in Nevada do the mapping they were out of Nevada using a Trimble GPS unit and we were in Bend and taken their data and tying it into you know other maps other data this stuff we had we were both working in nad83 state play Nevada East etc etc but the data from the GPS was consistently 50 feet north of all of the data that we had been using roads everything else property lines and you know we looked at the specifications and the Trimble said foot and I think the arc just said foot and I forget which was different but when we looked at the definition of the foot that's where we had this little difference here and you would think that very very minor difference so for example the US foot differs from the international foot only at the ten millionth place but since we started since our zero was 8 million away you know you take that difference multiplied by 8 million and it came up to 50 feet so just an example of being able to look at your coordinate system specifications these details how you can use this to help solve issues with the coordinate system where things aren't lining up your data is not lining up and here's another little example so this is the international headquarters of juniper GIS and if I measure my dining room table using US feet it sits over here and if I measure it using international feet sits over here which is location of the bathroom that's probably not a great place for a dining room table so just a little example of you know how some of these seemingly minor details you know can have an impact on you know your analysis and your data and stuff ok ok so UTM coordinate system used often by federal agencies so Forest Service BL and you us used to use you team a lot they're shifting over a little bit to other formats units are usually in meters based on that transverse Mercator projection where we take the cylinder turn it sideways so our north-south line is true usually has a false northing of false easting so all units are positive and schematically this whoops I'm ahead of myself here these are all the UTM coordinate systems so there's 66° slices across the globe I happen to be in UTM zone 10 when you're in Kenya or UTM 36 I think this is 36 maybe 37 so basically you know you've got all these 6° slices going around the globe and you have 60 of them and then schematically the way this is laid out is if we're looking at the northern hemisphere okay the 0 for our vertical values are in this case latitude okay and now actually see our vertical value in meters okay the 0 is is the equator that makes sense but we have a false easting 500,000 meters from that central meridian and all that means is at the equator we have to go more than 500,000 meters before we start getting into a negative value okay so again false easting false northing is just to get away from having negative values within our coordinate system if you're working with the southern hemisphere okay you still keep the same false easting 500,000 meters but you have a false northing of 10 million meters which puts you 0 0 way down below your area of interest so that when you're looking at all of your vertical back now I should say vertical but your y-values north-south values they're going to be positive values than negative okay Uttam corner system on the equator so just a little example here so Kenya it's on the equator Columbia and number of other countries Ecuador I think's on the equator yeah what we do here is in this case here they have selected a UTM zone 37 north so a north UTM zone but then what they did is change the false northing to ten million so that when you're working down here in the parts of Kenya that are below the equator for your north/south values you don't have negative values okay so again the false easting false northing is just to get us away from having those negative values and we have something on the equator with the UTM where normally the equator is zero even if we're calling it a North UTM zone we add in the false northing a ten meter and then life is good excuse me for a second throats get a little scratchy here so I've been using us exhale so I just want to show you a couple other other examples just so you realize that all of these same principles apply to anywhere that you're working so this happens to be Bhutan and I can go look at all the specifications for the different coordinate systems in Bhutan and actually they have one National Grid and then they have an individual grid for each one of their districts kind of like stapling okay so we have individual districts and I can look at all the specifications and they have a false easting of 250,000 meters the central Meridian is ninety which goes right through here and my East line here's where my zero is from my East line is over here that's two hundred and fifty thousand meters away from our you know 90 degree mark here and stuff and here's a little example for South America so Argentina they have seven different zones okay and they span different UTM zones in here and you can do the same type of thing that I did with the Oregon State plane and the Nevada State playing zones in terms of lining out you know where your central Meridian is and all the other values in this case because of UTM the primary factor here is our central meridian as we work at the different zones for our Janina that central meridian would just shift to be closer to basically the area of interest and just a little bit showing the zero zero for our argentine zone seven specifications so this is always a fun thing to do with the different coordinate systems you work with it can really help you understand what's happening when you look at all those numbers inside your coordinate system okay so hopefully you know enough about ellipsoids projections datums and coordinate systems to understand why some systems have been used okay hopefully you can also better understand what is required when projecting data or when you have problems with projections okay so you should know how to determine parameters needed to project data from one system together so key parameters look for our coordinate system projection type of datum type of spheroid like I mentioned one agency at one point was using a uncommon name for a datum but knowing the type of spheroid led me to know which datum they were using something like that standard parallels and meridians false tasting false northing units okay so hopefully you can understand you know all of these are you have a better handle better grasp of what they mean seriously it took me a few years when I first started with GIS back in early 90s to really get comfortable with all of these values and stuff now working with projections in ArcGIS so David needs to be in the same coordinate system for analysis aren't just needs to know the coordinate system of the data and you can find this in a lot of places if you work on shapefiles or if anyone can still remember coverages there's a little file called not prj for projection that has a coordinate system information you might have world files if you're working with TIFF images JPEG image is CAD files computer drafting files might be auxilary files that might be within a geo database but somewhere hopefully attach that piece of data that you're working with there's additional information that tells ArcGIS what the coordinate system is okay and if I'm going to do analysis I really want to make sure that data is in the same coordinate system now you can find this in several places so you know if you all work with RJ s a little bit you've seen some of this but you can go into our catalog go to description meta data spatial if you go on arcmap you go to layer go to properties go to source our catalog properties XY coordinate system arcmap data frame properties coordinate systems layers this is nice this is a slightly earlier dialog box here for layers but when you click on layers what they used to do is they would list each piece of data in your map and then the coordinate system starting I think with 10 3 or 10 4 they list the coordinate system and then each layer that's used on particular coordinate system but this is a quick way to see if you have more than one coordinate system going in your map ideally everything is in the same coordinate system and especially for analysis where you're going to start slicing and dicing your data Cliff's intersect Union whatever you know all of the data that you're using for analysis should be in that same coordinate system and then going into data properties coordinate systems layers quick way to see which coordinate systems are working or are being used in that mxd a little bit on the arcgis coordinate system dialog so they change this in 10.1 and they actually added a couple things in here so nice thing is spatial filter if you turn on the spatial filter and you start searching for coordinate systems that you might want to use it's only going to show coordinate systems that apply to your particular area of interest so you have to have at least one piece of data in and maybe you are working with wgs84 latitude longitude and you know you have one country one piece of data in and aren't yes will use a spatial filter to narrow down your choices from you know twenty thirty thousand and maybe just several thousand that's still nice another nice one add to favourites so if a coordinate system is listed down here that you're going to use a lot click on add to favorites it's added into your favorites you don't have to go searching through it anymore and then add or import coordinate systems so this is a situation where you might have a custom coordinate system okay and you can bring in a piece of data with custom coordinate system it'll be listed down here you can think I'll add to favorites or click on this drop-down you get a dialog box where you can point to a piece of data sometimes to make sure you got the exact same coordinate system as other data in the map sometimes rather than choosing off the list here better to go click on here and import the coordinate system from an existing piece of data and then you'll make sure you have you know everything you need you can also on this little example of the favorites you know add to favorites or move to favorites and stuff and a little bit of example of geographic coordinate systems transformation so this is that geo transformation we're talking about I'm going to demonstrate this later on now a few things I'd hopefully are obvious if you've been working with GIS for a long time or a while coordinate system can be defined in our catalog is a property of the data in our tool box using projections define projection tools so defining this is the situation where you have data from someone but there's no coordinate system information but maybe you know what the coordinate system is so in the old days we were really sloppy and there were five of us using GIS over here in Deschutes County Oregon and I knew if I got data from the force for my friend bill over in the Forest Service it was in UTM zone 10 at 27 so if he gave me something that was missing data and that's not unusual you know we were just both kind of sloppy I would go in and define it that piece of data and everything would work and the same thing I gave him some data and I screwed up somewhere along the line he knew I was working in Oregon State playing south that 83 he would go define the projection so defining is when you know with some reasonable certainty what the coordinate system is for that piece of data but for some reason that information did not come across you don't have the projection file the dot prj you don't have a TFW world file or whatever okay the coordinate system can be changed using our toolbox of projections for jet tool okay and when you do that you end up with a second piece of data in that new coordinate system now important to understand the difference between defining the coordinate system and projecting the data to a different coordinate system so I have run into this a couple times getting data from people a little new to GIS and they thought all they needed to do is maybe change the name of the coordinate system using the defined coordinate system and that just doesn't work okay but if you have some errors and data that may be one possibility is that someone put in a wrong definition or defined it rather than actually projecting have run into that a couple times projecting data might also mean change in the datum by using a specific geographic transformation and I'll demonstrate this also a couple times when changing datums you have a choice of transformations so most of you have worked with this you click on the little button here you get 78 choices okay how do you know primary place I'll show you some examples of this is when you install ArcGIS somewhere under you know it's going to be ArcGIS desktop 10 point X ten point three ten point four whatever documentation there's a eighty page PDF file Geographic underscore transformations that list every possible combination that our chest Ezra knows about and then what transformation to use okay you can also search for article 21 327 in ArcGIS support it will get you primarily to the same place and I'll show you a couple examples of what this file looks like okay here what I'm showing you here this is an earlier version of that file it's projections name web doc it's used as an earlier one and it gives me all the choices I want to highlight a couple choices in here so for Mexico if I'm moving me if I'm working between North American datum nad27 2ww just 84 in other words if I got some GPS data and double just 84 I need to line it up with the existing day that's nad27 then I need to look for a particular transformation choice here that suits my area of interest good for my area of interest and the one that says underscore 18 is from Mexico one says underscore two is for police and I'll show you why I'm highlighting these where I work most often in western United States I see the one that says underscore six united states contiguous states west of Mississippi so here's one example of where you find these starting with 10.1 our chests will not always give you choices when you do your geographic transformation they choose the one they think is best and sometimes I'm not always sure their choice is correct but let me give you a couple more examples so this is the geographic transformations PDF file that I mentioned a couple slides earlier that's stored in that documentation folder so I'm moving between old Hawaiian which is kind of their equivalent of nad27 to WGS 1984 and i have underscore one underscore two and a score three underscore five etc I have one two three four six different choices so when I get this drop down list how do I know which one well here's how you know you go take a look at these choices then you go take a look at your area of interest and you also look at minimum latitude minimum longitude maximum latitude maximum longitude so Hawaii the state of Hawaii several islands actually probably a few hundred island stretches out quite a lot say for example I'm working on the Island of Hawaii they call it the Big Island well this one here which says USA Hawaii Island Hawaii on shore well that's more specific than USA Hawaii on shore or USA Hawaii Maui Kauai Lenni Molokai etc so that looks good to me the other thing you can look at is the minimum latitude minimum longitude maximum latitude maximum longitude and what I look for is one of these methods that covers the smallest possible area so I can see here that this goes from eighteen point eight eight latitude to twenty point three three in latitude which is smaller than eighteen point eight eight to twenty two point two nice that's give me a smaller area and if I look at the longitude minimum maximum longitude the same thing has given me a smaller area and in general when you think about distortion the smaller the area of the globe we have before we project or push a flat the less Distortion so those are the types of things that I look for and fortunately for most most people you'll need to learn two or three of these because I work on projects all all over the world you know I'm I'm in this document all the time looking for these but this is what you look for you look for the two different datums and don't worry about the order maybe you're working from W just eighty four and your GPS to a different datum but don't worry about which one is to the other one as long as you see both of your datums you're good and then you could work down through the list and you see which one makes the most sense is most appropriate okay here's a couple things I found on arc scripts arc scripts is no longer supported it used to be everyone put their scripts for the old ArcView 3x up there but you could still Google on arc scripts and get here and I don't know Robert but I really appreciate the fact that he kind of mapped out where these different transformation methods Geographic transformation methods work so it's kind of nice to see and this one here is from nad27 to WGS 84 you see all of these different areas and I mentioned earlier how highlighted earlier that for Mexico you have the NAT 27 to W just 8400 score 18 that was from Mexico the one the method that ended an underscore 2 was for beliefs well I was working in this area over here doing some reef habitat work with a group and to me the one the datum transformation that was underscore 2 would be much more applicable because it's much closer to my area of interest then say a datum a geographic transformation method that was based you know way over here in the middle of Mexico in 10-point oh I could make that choice in 10.1 art just doesn't give you that choice now for practical purposes it may not make a difference there might be a difference of a few inches or something okay but this illustration here what I want to point out here is that yes you have that list of where all these different transformations are effective but sometimes you might need to apply a little bit of logic okay in this case I was way off the edge of Mexico much closer to the transformation the geographic transformation set for police and to me you know using the one that was for police actually would make more sense I may have been wrong but you know I'm just trying to apply a little logic here okay and then here's another example nad27 and nad83 just some options and stuff now when you're working in 10.1 and you click you're in your projections or you're working with geographic system transformation you click on your choices and you get that long list of choices for your geographic transformation okay starting with 10:1 yes Roy has put these in the order of what it says his preference is best again I'm not quite sure you know that's true because when I'm working at 83 and ws 84 I've always used the underscore five I continued to use it just for consistency so that I know when I'm moving data back and forth between dojust 84 and that 83 in my part of the US you know I'm consistent but if you're in doubt again this is where you go to the geographic underscore transformations PDF file and you look up your different options and you look at you know your different values in here now there is one column called accuracy but I cannot find anything in this documentation that tells me what that accuracy measurement means I don't know if a smaller number is better than a larger number but again what I look at is the area of coverages by looking at the minimum and maximum latitude minimum maximum longitude and I kind of decide from there what I want okay but just to let you know starting with 10:1 these are in order of what ESRI thinks is the best options probably not going to go wrong if you choose those but if you really want to dig into it that's when you need to go back to that geographic transformations PDF file now in some cases you might need to do two transformations for example if you're working between nad27 North America dam 1927 and you're working to 1983 Harn I actually reference network okay and I ran into this Weiss teaching some classes in Washington State there's no method that goes directly from nad27 to nad83 horn but what you do is you bring select the geographic transformation it goes nat 27 and nad83 in other words you get one step and then RGS gives you choices for the next step so this is actually a smart dialog box okay click the drop-down you pick a choice if you still need to pick other options the drop-down button still stays Actress that's kind of nice starting with 10:1 what they did is they actually combined these on one statement for you so that's kind of nice now our Jes will also project de as part of most geo processing operation so geo processing operation anytime you run a tool in our tool box as a jewel processing operation I don't know how many people use environment settings but these are like setting defaults for you tools in our box-and-one default you can set is the geographic transformation and you can actually put in two or three so if you know in this particular MXD I'm working between three different coordinate systems and two different datums or three different datum Sivan you can put in all your possible combinations here and then if you do something that's going to cause a projection ArcGIS will go to the environment settings for Geographic transformations and it will pick the appropriate setting for you so this is just kind of a little safety measure just to make sure you don't a lot of analysis you might be changed in projections uses some tools and then you'll make sure you're using the correct geographic coordinate system now project on-the-fly yes you're all used to project on the fly because unless you go all the way back to RP 3x and arcinfo workstation ArcGIS has always been project on the fly okay this can be pretty good but just a couple things to know so coordinate system must be set for the data frame or just need to know what coordinate system you're using okay transformation methods can be set if you know the specifics specifics excuse me of the data being added that's why you need that projection file the projection information works on raster data as well as vector data this is nice because until recently projecting raster's was kind of a pain this is really nice project on the fly is not as mathematically rigorous as use of the project tool so I've had some try people tell me that it's really a rubber sheet and not a true projection but I'm going to show you how if you're paying attention to details it works really well but best procedure for highest accuracy do all projections through the project tool rather than relying on project on the fly all the time okay another little thing about project on the fly if you have data from several coordinate systems and even if you're not doing an analysis but you're just worried about your display or just concerned with display every time you zoom in and out ArcGIS has to recalculate in other words redo the project on the fly where all your data is sitting so it'll actually slow your system down a little bit if you do have data with several different coordinate systems inside your data frame so even if you're not worried about analysis which you should be it's just more efficient to have all the data in your data frame in the same coordinate system okay and you can also modify a projection I'm gonna demonstrate this a little bit later but basically in 10.0 you'd select the projection click on modify and 10:1 you click on a projection go copy and modify and we'll show you how you can modify a projection to better meet your area of interest now here's one of the fun things about GIS how do you determine what projection data is in when there is no metadata ok so there's a few things you can do some will help some may not first thing bring data into an empty map and check some of the coordinate values in other words you know move your cursor around and look at that information in the lower right hand corner so if the numbers range from you know 0 to 180 or you know 0 to 90 then you're pretty sure it's in latitude longitude unfortunately you don't won't necessarily know which datum where I work in Oregon because I've been working these different coordinate systems I can almost look at these units and say oh yeah I know that's Oregon State playing at 27 or whatever ok so sometimes that can be helpful but some you know depending on the datums some can be really hard ok compare unknown data to a known reference layer so if you bring data in matcha was something known as lining up then you can be pretty sure that the data was created in the correct cordon system it's just that you know no one define the coordinate system or somewhere along the line when the data was processed the information about that quarter system got stripped out somewhere and that's where you can use the define projection tool or go into our catalog and go to XY properties and then ESRI is the help article which pretty much gets you to this point anyways okay so I want to do with free demonstrations I think we'll run a few minutes long okay but these demonstrations I think will help quite a lot so I'm going to switch over arcmap and we're gonna go to the Oregon coast so this is a Pacific Ocean over here in northern Oregon Coast Siuslaw National Forest and we have a bunch of owl nest threatened and endangered species in here and if I look at my data frame right click properties okay coordinate system I'm working in nad27 UTM zone 10 north so NAT 20 says my datum UTM zone 10 North that's my coordinate system okay and I have my all nests that are set to that okay but I got some new data actually not new data but I'm gonna pretend this new data I'm going to click my home folder button this is so nice it takes you straight to where your data is and go to Siuslaw Siuslaw data and I have all nest W just 84 so this is actually the the raw data as is collected and a GPS and I'm going to click Add and you get this geographic coordinate systems warning so I want everyone here to be honest and tell me how many of you just go here and click close because you're not sure what is happening with this dialog box okay I'm gonna go close and pretend I don't know what's going on oh those don't look too bad actually those red points well let's zoom in oops that doesn't look too good let's zoom in a little more maybe we'll get better looks like it's getting worse well let's do a measure on it and I'll measure distance in meters that sounds good so I'm going to go from our WGS point to our UTM nat 27 point and it shows we're ninety eight point one four seven eight eight four meters off well that's the difference between using the nad27 version of the globe net now 27 data datum excuse me and the W just 84 data because the datums are different shapes of the globe if I'm using different shapes my zero zero the start point for that coordinate system ends up at a different place on the globe and that gives me my by basically my error here okay of course yeah Suzy so let's see if we can fix this or do this correctly so I'm going to remove the wgs84 version I'm gonna click add data bring this in again sometimes it doesn't give you the warning box the second time around okay so what you really want to do when this dialog box comes up and it tells your your do using different geographic coordinates and remember geographic coordinate system same as datum okay click on transformations and then you come in here and you've got your choices of convert from while I want to convert from GCSE WGS 1984 to GCSE North American 1927 and I want to use and this is where you go Oh shucks too many choices okay so probably if you take the first choice that aren't just selects you're probably good but because I've used that table before that Geographic underscore transformations PDF I know the one I want is where it says nad 1927 to WGS 1984 underscore six that's a particular method I use what used to be nice is earlier our chests would tell you the differences here in the X Y and C that was useful information anyways they don't know so I'll say okay and then I say close and let me change this to red let me zoom in a little bit so now that I told Archie I asked the geographic transformation we're lining up I don't know if I want to say perfectly but I'm going to scale of 1 to 0.25 and I cannot see oops now I went to like almost a negative and now I can't see any difference now here's a little trick so I use my geographic transformation I said the geographic transformation so I know that when our chest did project on-the-fly the data lined up correctly now if I right-click on all nest there'll be just 84 and I go to properties and I go to source okay it's still telling me that this is in you know GCSE WGS 1984 so it's still it has not changed the coordinate system is projected it on the fly kind of temporarily for this M XD but here's a little trick I'm gonna go right-click data export data and I'm going to export it using the same coordinate system as the data frame in other words my nad27 north american datum of 1927 zone 10 north and I'll go save it I'll go to my default geodatabase so I set it right and I'm just cheating a little bit to get hollowness and I'm gonna call this all nest what's the March 15 2017 in other words I went out with my GPS I brought the data in I use my geographic transformation values I set them so the data came in correctly used and projected on the fly and now I want to save it in the coordinate system I'm using for my work nad27 UTM zone 10 and I'll give it like a little date stamp you know I'll nest as of March 15 2017 go save say ok I do I want to add it in yes turn off the old one you can see that's lining up correctly and then if I go into property source then we can see that we've picked up the projected coordinate system so I actually use this a lot when I'm building up a map I determine the coordinate system I want to work in I set that in my data frame as I bring in Davis in different coordinate systems set the correct geographic transformation make sure it's lining up use all the data select part of the data and then do this right-click data export data and use the same coordinate system as a data frame it's actually like performing a projection okay but in this case what I did is I was able to verify the data's correct before I actually did the projection so I use this quite a lot so this is pretty handy okay so that was project on the fly and what happens if you don't pay attention to the correct geographic transformation or if you just click close on that warning block so I'm going to close this sorry for the noise here we're going to switch over to let's do this where is this place okay so we're working in Uganda teaching a class there for Jane Goodall Institute and also working with a scholar Philip s each one of the segs scholars from 20011 and he had some data for this province women here and he could not get it to line up so I'm working in let's check my coordinate system right click properties' coordinate system arc 1960 UTM zone 36 north ok good whatever now I'm going to bring in some data so I'm going to click on the add data button click home go to Uganda go to Meg so this person Meg I never met her who created this data and I'm gonna bring in houma villages dot SHP click Add and it comes in change the color to red to make sure it shows up and it should be coming in right here let's open the attribute table boy all the values look good okay okay 487 records I don't know what's going on right click zoom to layer doesn't go anywhere well that's not working so let's go right click remove this okay so I'm going to start an empty arcmap take a couple minutes to load up and I want an empty map I want to add data I have to make a connection I should have remembered to make my connection beforehand computer main see that's close enough and I'll bring in my home village is that SHP hey looks perfect comes in nice and easy I don't understand the problem want to go back to our Uganda map for a second just a little note so here's the equator this is all north of the equator and we're using a UTM zone so remember in a UTM zone for your north-south values this is zero values increase as you go up here okay and if I move around and I'm looking at the lower right corner hopefully you can all see on the screen at a lower right corner this is about 155 thousand meters north okay let's go back to our untitled map and if I look at my values down here in the bottom load a lower right corner of my values it's ten million meters north so let's look at the coordinate system right click properties WGS 1984 that's ok different datum UTM zone 36 north ok transverse Mercator yeah this looks good but wait a minute if I'm working in 36 north these values shouldn't be 10 million okay so let's go fix this very easily I'm going to close this out I won't save my change is add data and I'm gonna bring in home villages UTM South shape and then I'll show you what I did so now we can see they're lining up let's just make them nice and bright they're lining up pretty much exactly where they need to be okay and I come in here right-click properties and I look at the coordinate system and what I did is I change it to south 36 south and I put in the false northing of 10 million or probably a little better I could have left this as UTM zone 36 north but just added the 10 million for a false northing so that it puts the zero value way way way way south of my data of where my data is located and then this would line up so I'm guessing what happened is Meg said oh yeah I'm working in the north part of or sheep Ruggiero maybe she projected it my guess is she might have projected it she says oh I'm in the North Zone because I'm north to the equator but didn't take into account when she projected into 36 north from maybe whatever system she had that uganda is on the equator or she didn't understand or know that you know if you're working across the equator to make your values correct you need that false northing of 10 million so you know Phillip had spent a lot of time looking at this but when I looked at this in the empty map and I saw the values of like greater than 10 million for something that should have been you know 155 thousand or something then because I know that for a if we're working with UTM zone Sal or a UTM zone that's spans the equator I want to put in that false northing of ten million so again it's a question of knowing the specifications of coordinate systems and how they work so that's what helped me solve this one so get rid of this one here and then the last one is we're going to modify a projection so this scenario here we have a woman we have a person studying the movement of vultures between Mongolia and South Korea and she wants to do a distance a distance matrix between all of these different points okay now the issue is the tool that will do the distance distance matrix needs a projected coordinate system and this map her data is in a is in latitude longitude wgs84 which is very logical because you're collecting a series of points over a large area that is the cordon assist you want to use for collecting that data but for analyzing it where I don't need to go to distance then I need a coordinate system that's projected and deals with distance so what I want to do is first find the distance between this point which is my northernmost vulture point and this point so I did these because I wanted to find the greatest distance and I'll go to my measure tool okay and we'll do distance and we'll do the kilometers and it's actually set to geodesic I can't do plane R because we're in a geodetic latitude longitude so let's just do our distance and notice how this distance line kinda has a little arc so we're following the globe okay and my distance is two thousand three hundred and twenty ooh kilometers so let's uh hit the Escape key get rid of that I'm going to properties here I just want to write this down whoops it changed I mean let me redo the measurement again normally I have someone write this down in the class but let's go do the measurement again and if I snap to it 2322 and I'm just gonna write that down now let's do it good to 322 and we'll say okay so I'm gonna choose a projected coordinate system so I'm gonna right click on layers my data frame go to properties I'm going to go to coordinate system I'll turn on my spatial filter okay and outline of features good vault countries give me some range here say ok and it gives me favorites hmm I'm gonna clear the spatial filter so I'm gonna go to projected and I'm gonna go to Continental okay so projected goes flat Continental large area Asia and I have Asia Lambert conformal conic albers equal-area conic Asia North equidistant conic Asia Northland whoops equidistant so I'm concerned about distance and I'm north so let's select this one and then we'll say ok and we see how our map changes a little bit I'm going to zoom in a little bit I'm going to do my measurement and I'm gonna measure again that same distance and I'm 2199 click escape go into properties for this just so we can write it down 2001 99 so we're about little over 123 off let's see if we can do better so I'm going to right click data frame go to properties go to coordinate system and I'm gonna right click on the one we're using I'm gonna copy and modify very important when you go copy modify change the name okay you don't want to overwrite an existing predefined you know coordinate system so I'm just gonna put vultures at the end okay and what I'm gonna do is I'm going to change my central Meridian I mean move this oops let me close this for a second sorry so if I'm looking at my data for my longitude I go from 105 east to about 130 east and lon latitude I'm going from 35 north to maybe 48 north so we'll just remember those numbers here let's go right-click properties go back to copy modify call it Bulger's and so my central meridian so I calculated the difference or the middle and 117 0.5 is the middle point between our 105 and our 130 okay in terms of our longitude and my standard parallel 1 well that's 35 that's where my lowest or further south vulture point is and my standard parallel second standard parallel I'm gonna make that 48 because that matches the latitude for this whoops don't leave 485 in there and then latitude of origin is 30 as long as the latitude of origin is south in this case of my area of interest that's okay so I'm gonna say okay here say okay here our map shifts again through a quick zoom out let's come in here do my measure Northwest to Southwest I'm 2317 versus 2322 so I'm within five kilometers and I'm gonna say that being within five kilometers over distance of 2300 kilometers is probably accurate enough for the analysis that I'm gonna do so at this point you know the person using this data can then go feed this data into that distance distance matrix tool that relies on a projected coordinate system and be relatively confident about how the data is going to work out okay so this is an example of you know modifying a projection and one thing I want to stress on this you modify a projection also change the name okay so you don't overwrite you know one of the existing standard coordinate systems and stuff so close this and I guess go to questions so Tasha you want to turn it over to questions sure we are running short on time so we'll keep it short and I think there haven't been a lot of questions come in but one one that says I'll start with says what do you do if you're given GPS coordinates and don't know data and are trying to bring the data in as a layer with other data layers and I think this one might have come in before you showed a specific slide on that but maybe you could just revisit that quickly yeah fortunately with GPS you can make an assumption and realize this is an assumption that the data was collected in wgs84 okay so what I would do is I would one bring the data in it and see how it does line up but generally what I probably what I would do is I would define the data where so remember define versus change I would you find that data to be wgs84 then bring it in and see how it works another thing on GPS unless you really know your GPS unit and the settings i highly recommend leaving your GPS to the default and then you will know that it's wgs84 but again it's an assumption it's a pretty good assumption that it's though just 84 but you can always can't always guarantee it another thing that you can do with the GPS pretty sure in garment and tremble if you export the data from your GPS as unprojected it will actually export it as W just 84 so hopefully that will help on that question there great I think yeah there was one more that came in about the Hawaii example it said why not choose the transformation with the highest accuracy because I don't know what the accuracy means I can not find any definition of what that accuracy is I feel more comfortable working with this to pick the smallest area but most of these the difference is going to be probably pretty subtle if you've been doing your GPS and you're under you know tree cover and stuff the difference you might get between choosing the different geographic transformation methods probably would not be very important at all I'm just going to what I learned and been working with for years is that you know I tend to prefer the smaller area of interest to me that makes more sense but you probably would not go wrong going strictly on that accuracy but I've never found definite definition what that accuracy is I'm assuming the smaller numbers the higher accuracy but there's no nothing in that file that tells me great thanks John well I want to thank all of you for all your interest and as soon as we get the video process we'll we'll post it online as well as make the slides from the presentation that that John has walked us through available with a link so I will email all of you within the next few days with a link to the recording and a link to where you could download the slides and John I just really want to thank you again for excellent presentations really appreciate it and do you want any last comments well a little advertising if you go to my links play page there's other references I mean other presentations you can download and also feel free to email me it's just John and juniper Jess calm if you've got projection questions I always learn what I'm trying to solve other you know projection issues so it's always good for me to have some other problems so feel free to email me we've got some coordinate system projection problems or questions great well it's quite a few comments coming in thanking you for an excellent presentation so thank you all and be tuned for the links and follow our pages to find out about the next webinars so thanks everyone have a great day okay see y'all I'm gonna log off okay thanks bye

Channel: databasin

Views: 35,682

Rating: 4.9444447 out of 5

Keywords: SCGIS, CBI, GIS, spatial data, projections, coordinate systems

Id: -2z_WP7N7to

Length: 98min 2sec (5882 seconds)

Published: Wed Mar 15 2017