Getting back to GIS basics Features, Feature Classes, and Layers

[Music] hello everyone and welcome back to another instructional video from eg is associates today we're gonna get back to basics we had a viewer from one of our earlier videos that really requested that we get in and kind of talk about the relationship between features feature classes and layers and how that all works so that's what we're gonna do in in this video we're gonna kind of get back to those basics is anyone that's worked in GIS knows we do things a lot differently we don't have a single file type or a single data format and this often causes confusion with new users coming into GIS because they're used to you know with word you open a do see or do see X file or Excel an XLS file or an auto you know AutoCAD with DWG files or dgn files for MicroStation they're used to that one file that works with their application and GIS just doesn't work that way we have multiple file types multiple file formats and we do this largely because of the size of the data we work with in GIS it's not uncommon to have a data set it is over one gigabyte in size we even approach terabytes in in some organizations they may even get higher into petabytes worth of information and if we tried to load all of that data into a single file you would pretty much kill any computer even some of the most powerful ones out there so what we do in GIS is we divide those data sets out into individual files into individual feature classes into different data sources and that also brings up the fact that in GIS we try to leverage data that's coming from different locations so we may pull data in from a web service or we may pull data in from a local shapefile we may pull data in from an enterprise database somewhere and bring all that in mash it together in a single map so that we can then perform analysis see relationships and as a result because this data is coming from all these different locations you know we have to be able to work with that effectively so these are reasons why in GIS we don't have just a single file you don't just open a shapefile or you just don't open a map file all these things are interrelated so what we want to do now is really get into kind of the the bare-bones right the basic foundational understanding of when we're creating a map what is a feature what's a feature class and what's over a layer and how they are related to one another so a feature which is kind of at the core of everything is a representation of a real-world item that could be a parcel it could be a fire hydrant it could be a zoning boundary it could be a power pole a transformer and so on right it can represent any sort of real-world item and we're going to do this by choosing how we represent it as either a point a line or a polygon that feature is then also going to be linked to an attribute table or a database table in the back end so that various attributes associated with the feature are also collected and connected to that feature so that if we select as we see here in the slide a parcel then we can open the attribute table and see things like what's the lot number what street is it on you know potentially we could have the owner's name we have the size and acres we have fields for the centroid X&Y coordinate values so we can control what attributes are connected to that feature and they're going to take a group of features like parcels that you see here and store those in a feature class so a feature class is a collection of features that share the same geometry meaning they're gonna all be points or they're all going to be lines or they're all going to be polygons in a single feature class you cannot mix and match feature types or geometry types so they all will be again points or there will be lines or they will be polygons so all of those features are grouped together usually based on what they are like you're gonna put all the water valves in one feature class and all the fire hydrants in one feature class all the parcels in one feature class you have to do it that way no for example you can see the line feature class illustration here on the slide where we're showing looks like road right-of-ways parcel boundary lines in some sort of utility line those are all lines so they could theoretically all be stored in a single line feature class we wouldn't want to do that because the other part of a feature class is that all the features share the same attribute table that underlying database table so to keep that table under control meaning we don't have a list of fields or columns in it that extends you know well off the screen of any computer we tend to group like features in a feature class so we would put the road right-of-ways and potentially the parcel boundaries because those all form part of the the boundary of a parcel in a single feature class we would have water lines in a separate feature class from sewer lines and that kind of thing again to try to keep the attribute table under control yes theoretically we can't put all of those in one feature class if we wanted to but then your table is going to get out of control with the number of fields or columns it's got to contain in order to store all the information about the features in the feature class that you need to store and use in analyze okay the other part of a feature class is that all those features that are in that feature class are going to share the same spatial reference so what does that mean spatial reference it sounds like a big big word big term it's really simple it's they all share the same coordinate system there's a little more to it than that but in very basic terms they all share the same coordinate system they're all in your local state plane coordinate or they're all in UTM zone whatever or they're in wgs84 whatever your whatever coordinate system you assign to the feature class when you create it all the features in there are going to be stored in that feature class okay then we're gonna as we create the feature class the feature class itself is actually going to be stored in a specific data format okay so there are a lot of different formats that we can use in GIS but the feature class is going to be stored in that so let's talk a little bit quickly about different data storage formats that we use in GIS so I'm going to touch on just three here there is a lot more than just these three but these are three of the most common especially for those working inside of the ESRI ArcGIS environment so the the first and probably well say most common but one of the most common especially for those again working in the ArcGIS platform is the geo database so the geo database is a relational database that stores feature classes a single geo database can store multiple feature classes as you see here we have a geo database that's called GIS underscore CAD underscore demo gdb so that's a geo database and then within that we have feature classes so you can see we've got other groupings in here feature datasets but in the Royston feature data set we have a city limits polygon feature class we have a clip area polygon feature class we have a road underscore CL line feature class also down below that you'll see a hyd underscore fire which is a point feature class so those are all individual feet your classes so in each one of those we have a collection of features that share the geometry which is indicated by the icon there and that common attribute table and the same spatial reference we can also work with CAD files I know that most people in GIS or even in in the CAD arena with engineers surveyors don't really think about a AutoCAD file or a MicroStation file containing feature classes but from the GIS perspective it certainly does and you can see that we have points polygons and a polyline which is basically the same thing as a line all stored in that one hydrants DWG and in the world of ESRI an arc whether it's arcmap our catalog or arcgis pro we use blue icons to symbolize a CAD file whether it's a DWG DXF or dgn those are all just CAD file data formats DWG and DXF or associated mostly with autocad from autodesk dgn comes from MicroStation from Bentley which is a competitor to autocad but they're all drafting packages used by surveyors and engineers and landscape architects in those types for data but we can pull that information in to our GIS and use it whether it's it's ESRI or others like QGIS manifold and all that can also utilize some of these very same formats and then we have shape files that's a good old every format probably the most common GIS format out there because all GIS software can pretty much read a shape file a shape file is going to store a single feature class so it's going to be a point shapefile a line shapefile or a polygon shapefile I actually have videos both on shapefiles and geodatabases that I'll link in the description below so if you're not familiar with either one of those you can go to those videos and watch them geodatabase one's actually a three-part series I did several years ago was actually one of the first video series we've done on this channel so make sure you have links to that so we've got features features are stored in feature classes those feature classes are then stored in a specific data format be it a geodatabase cat file or a shapefile or something else ICO KML from Google or a mid or MIFF file from app info coverage files from old arc info GIS so again we're to put that so how does that all relate to a layer well a layer is how we visualize the features that are in our feature class so we're gonna add the feature class to a map and when we do that it becomes a layer the layer then references back to the original feature class so in this example you see on the slide here we have a parcels layer that has been added to our map that layer is going to reference or point back to the parcels feature class that is in our geo database in this case it's in the trip ville underscore GIS geo database so the layer doesn't actually store the data it just controls how we visualize it within our map so this can include the symbology in this case you can see we've got it with a light green fill in a kind of a gray outline and we can also control the attribute field visibility so those columns that are in the attribute table we can choose whether we want those visible or not visible and again that's a property of the layer we can control labels with your text based off values we find in the attribute field we can control scales at which the layer turns on and off automatically call those scale visibility ranges we can apply filters so we only see certain data based on a query that we build this is called a definition query and there's a whole lot more but a layer just controls how we visualize the data that's in the feature class how do those individual features look as well as the attribute data associated with it so they they don't store the data this is something that is very confusing that layers and maps don't store data they just point to data hey and that does bring up the bigger picture is that a layer is then stored in a map as you can see here we've got the map at the top of the contents there and then the various layers underneath it right and then each layer is going to point back to its reference it's data that it's where it's stored right so hopefully that makes some sense so we can see that here as the full relationship so again we've got features all the individual features we've chosen to store them as either points lines or polygons in this case we're looking at point features those features are stored or grouped in something called a feature class and then that feature class is part of a bigger data format via a shape file geodatabase CAD file and so on and then we're gonna add that feature class to a map so that it creates a layer the layer references back to the feature class the layer doesn't store the data it just controls how we're visualizing that information so you can see here I've got a manhole feature class and I'm visualizing or symbolizing the data based on its condition is it fair good poor or unknown so again layers not storing the data it's just controlling can't we visualize it right so let's kind of jump into desktop GIS application and see how this works so you can get a better visualization for the whole relationship between features feature classes and layers okay so we're back we're in we're actually going to use our GIS pro to kind of take you through this this concept the same applies for arcmap same applies basically to QGIS map info and any other application out there but we're gonna use art pro for the sake of this demonstration so we're gonna start out in talk about features and look at a feature so you can see here I've got a map I'm looking at parcels here so each one of these items each one of these boundaries represents an individual parcel and this is a feature right so this is one feature this big parcel here's one feature this parcel little parcel here's one feature and so on so each one of these little boundaries these polygons are individual features they are also linked back to the table so each one of those polygons we're looking at has a record over here in our attribute table which stores the various information we want to associate with each feature again this is as you design your data you will choose what fields need to be here and all those kind of things but you see here for each parcel I've got information for lot number street number street name that it's off of the suffix for the street is it a street a court away and so forth shape length which would be the in this situation the perimeter around each individual parcel shape area which would be the total area in this case it's going to be in square feet because I'm the coordinate system I've assigned to this feature class is Georgia state plane which is in feet acres self-explanatory arian acres I have not got a field to hold the perimeter and whatever unit I want to it's not been populated and so on so we've got the various fields associated with each feature right so each one of these that you see here right coincides back to one of the rows you see here so the feature is both geometry and tabular data now all of this is stored all of these features are stored in a feature class so you see that here I've got the parcels feature class sitting right here and there's other feature classes that are in this geo database right so and this is something called a feature data set it's just kind of an organizational container think of it as a folder within the geo database in laymen terms but you can see here I've got the parcels feature class the natural water stream feature class natural water body feature class County limit feature class city limit feature class so each one of these feature classes is going to contain groupings of related features like all of these in the railroad tracks or railroad center lines right all of these are parcel parcel polygons for the area shown me so again they're all stored in this feature class and each one of these feature classes has properties right so we can see it's a file geodatabase feature class that's the data type we can see the database that's stored in that's the source the location we can see the name of the feature class we can see the alias which is just a more descriptive name if needed we can see what feature dataset it was in which was the base featured a see over here base that's the feature dataset so again telling us where it's at it's a simple feature class meaning it's just a point line or polygon and in this case it's a polygon you can get into complex feature types Multi multi feature things and so on don't need to talk about that yet we can also see that it's not storing Z or M values in here so elevation or measured values we're not going to discuss those here it does not have any attachment so it doesn't have any links to photos or other documents and things those haven't been enabled and feature Bening is also disabled so continuing down from the feature class we can see the extent so this is the minimum maximum XY that this whole thing covers here's the spatial reference that I was telling you about so you can see this is in nad a3 State playing Georgia West Phipps it's a transverse Mercator projection it uses u.s. survey feet this is the fall seating easting and northing so all the information about the coordinate system in the projection is stored here so all the features in this feature class are in this coordinate system and projection okay so we see feature classes have other properties so in get into indexes I'm not going to go into that in this video that's a more complex thing we can set relationships between this feature class and another feature class with all - that would be in here and then location referencing that would be if we had in values enabled which we don't so but you can see the basic properties of the feature class and so these whatever setup in here would pull it down to the individual features here because these are all stored in this feature class right which is then in turn stored in this feature data set which is stored in this geo database we can also go down and look at other types of data so here's a CAD file and here's a DWG file so again we can see that this feature data type or data format I should say stores multiple feature classes and I can select and look at those and even though it's a CAD file you can see it's got spatial data coming in I can look at the table because it does have attributes these are fire hydrants or pulling from or looking at right so again we see this one DWG file is stored multiple feature classes but each one of those feature classes is a collection of features that share that same geometry and the same attribute table again it doesn't matter that it's a DWG and not a geodatabase we can also go see here if I can find a shape file somewhere I'm sure I can yep here we go so here's a another shape file so you notice the green icon here so this is a shape file notice this only stores one feature class unlike our geo database and our CAD file this there's no drop-down or nothing here to expand it's a single feature class but again you can see there's the table and here's the geometry showing the individual features so now we're going to take that and expand it and go into a layer so I've got this map that I've already created and you can see there's the manhole layer that was in the slide we looked at earlier and again if I open the attribute table you can see the attribute table down here right and these two are linked together so if I go up here on the map and I select that manhole I'm gonna make it so I'm only seeing the selected record down here there's the attribute record associated with that if I select this manhole this is the record associated with that manhole so all of this data applies to that feature or and I select this one this data applies to that feature okay so this layer is referencing back to that feature class and we can see if we right click on the layer and go to properties we can go to source and you can see here that that layer is pointing to a file geodatabase feature class that's the located in the trip ville underscore GIS geo database and it's the manhole feature class that's in the sewer feature dataset so if we go over here into the catalog pane you can see there's the trip ville underscore GIS geo database here is the Sewer feature data set and I need to close that down to expand this and there is the manhole feature class so this layer here is referencing back to this feature class here this map is not storing the data it's pointing back to this data source all of these different layers are going to point to their appropriate data source you can also go in either arc pro arcmap in the contents and this little cylinder icon here is lists by data sources this will tell you where your layers are pointing to where are they coming from so you can see I've got different sources for these two layers these are coming from a folder which means they're either a CAD file or a shape file this little icon here the little blue line connected to a little vertical rectangle that looks maybe like a mini computer these are web Web Services so these sewer lines here are actually coming not locally anywhere on my machine but actually pointing back to a service that's hosted incoming via the web right so all the sewer lines are coming from the web my manholes my railroads my parcels are all coming from the trip ville GIS geo database and then we have another web service so our water system water lines or water service areas are also coming from a different web service so I actually have two separate web services referenced in this one map and then my base map is also coming from a web service for your ArcGIS online so you can see here a single map each layer we have is coming or pointing to a different source so again if we had to try to store all of this into one single map that would be the maps would be huge right and again your your system would then suffer as a result of having to load all of this into memory at one time for display and all that so we just reference these data sources in so we're never loading all of the data in so that as we pan and zoom you know it's going to determine what data is visible and low just that bit of data into our system so we're never loading the whole thing in this allows us to work with these big data sets and do so efficiently and effectively in a way that doesn't crash our system every time we try to use it I'm saying GIS does it crash but we can work with a lot bigger data sets then say AutoCAD can or MicroStation there or whatnot it also allows us to pull data from different locations instead of everything having to be locally on our machine we can pull things from the web we can pull things from servers from relational databases and things all into one map and again this just controls the visualization see when I select a layer the manhole layer up here I get tabs that are appearing so our appearance I can go up here and change the symbology for the layer right now it's being symbolized based off of its condition I could make it so they all look the same if I wanted to write or maybe I want to symbolize it based off of some numeric value in there so maybe based on depth for example sewing an idea the depth of each manhole in here so that's again just visualizing the data I'm just controlling how I visualize it if I want to I'm gonna go back to my values and the condition that in there I'm not gonna change everything back but you're given the idea and that's just one part of it I can also go here and label each manhole again this is just how I'm visualizing it with its manhole id sure and go turn turn on those labels and so now I'm again taking data part of that attribute table and visualizing the manhole idea associated with each manhole on here I can go and control data so if I want to turn off certain fields so when people are opening the attribute table or identifying or not or clicking on just to get some information you know if I don't want them to see things like say the object ID for example which is a field in the database that's solely used by the software right it's really not something that you the user need to concern yourself about nothing you can change or edit so turn it off why why look at it I think see it's read-only anyway if there's other fields a shape you already know it's a point because you can see based over here in the contents what type of data it is you can turn that off and this is controlling the visibility of those fields in the attribute table so once I save this change and close that down when I reopen that attribute table you can see down here that those fields the shape field and the object ID field which were at the start are not visible right so yeah that's all the layers doing is controlling how those how the features in that feature class the layout references are displayed and there's a lot of other things we can do here so again if we go to properties there's another way and go down here and do a definition query so I'm filtering out data so I only see where depth is equal to regressing greater than or equal to 4 ok so again I'm filtering out so now I'm only seeing those main holes that are 4 feet or greater in depth okay again I'm just controlling the visualization all of the data is still there I'm just filtering it out so it's only visualizing those that meet that definition query so this is part of the layer I'm go ahead and remove that ok so now we'll see all of them again ok so hopefully that gives you a much better idea of the relationship between features feature classes and layers and I should point out that a layer is going to be stored in a map and that layer which references a feature class can be used in multi Maps which is another reason we do this in GIS why we keep things separate because we utilize that same data across the board in multiple maps and multiple projects and so forth and so on so anyway I hope that's cleared some things up and now you have a much better understanding of what a feature is what a feature class is and what a layer is these are very core concepts kind of foundational concepts to anyone getting started in GIS because it as I said earlier it's very different the way we do things in GIS is compared to what you would do in other applications in AutoCAD MicroStation Word Excel PowerPoint any of those out there so with that again thank you hope you've learned a lot if there's anything we can do to help you with GIS please reach out to us we're always here to help we offer a full breadth of G is related consulting services whether you're just trying to get off the ground implementing GIS or maybe you have an existing GIS that you want to expand into the enterprise we can help you with that if you're trying to integrate GIS with other solutions like work order management utility billing permitting whatever we can help you with that if you're just trying to figure out how to even get started or maybe take your GIS to the next level and you need a plan a needs assessment we can do that for you as well maybe you've got a big project coming up and you don't have enough staff or maybe you need some GIS work going and you don't there's nobody near you we can help you with Renault tech services so we augment your existing staff or provides you with maybe your very first GIS staff person there we do that remotely your own site however you need that and of course we offer training and support so if you need a safety net know how to do some of these things or whatnot we can certainly set you up with a good support contract if you need help getting your staff up to speed on say ArcGIS pro or or ArcGIS Enterprise our coline or whatever we can certainly help you with that so please don't hesitate to reach out here's our contact information you've got our website at WWE is soch calm give us a call at six seven eight seven one zero nine seven one zero or email us at info at EG is so she's calm so that thanks so much if you liked the video please make sure to give it a thumbs up if you haven't done so already please subscribe to our channel and hit that little bell so you get notifications when we post new videos I do apologize it's been a little while since we posted one but there have been a lot of crazy things here happening at eg is that hopefully I'll be able to tell you about very soon so with that you all have a great day and hope everyone has a very happy in merry holiday whatever you you choose to celebrate and we'll see you in the next year

Channel: eGIS Associates

Views: 3,659

Rating: 4.9466667 out of 5

Keywords: ArcGIS, Basic, Fundamentals, GIS, Esri, Maps, layers, features, feature class, shapefile, geodatabase, understanding, core, knowledge, beginner, concept

Id: 9e8YXFgEqZ8

Length: 34min 9sec (2049 seconds)

Published: Fri Dec 20 2019