Georeferencing in QGIS # Lesson 11( Part 2) of 29 # QGIS Tutorial.

[Music] [Music] hi welcome to this qgis tutorial lesson 11 part 2. in this video we'll learn how to georeference in qgis using the georeferencer plugin if you haven't subscribed to my channel please do so so that you can get a notification when i upload the next lesson if you are new to my channel you can follow all my previous lessons from the links in the description box below let's get started so in our previous lesson we learned how to download google apps pro and also install we also learned how to download topographical maps that are going to be using in this exercise for the regional of your choice geo-referencing is the process of assigning real-world coordinates to each pixel of a raster when you reference your rasta you define its location using the map coordinates and assign the coordinate system to the map frame so let's go to qgis and perform first you're referencing on the top map that we have downloaded for region so i'm going to open qgis and my qgis i have a blank project so before i do anything in my qgis i just confirm to you that the data that i'm using is from a region that i downloaded from the google earth and it's underworld and it's under the scale of one to a million and it's in this region here in sudan where the river nile passes and meanders very very nicely so i've actually downloaded this this data here from the us army and this is what you're going to be using in this exercise you can also download data for any region of your own so let me now load the topographical map into a qgis i'm going to go to layer because it's a raster layer we're going to add a raster layer so i addressed a layer and i'm going to browse where my raster light is and it's under gis data and it's your referencing actually down created a folder called generating i'm going to select this is the data that i downloaded it's a jpeg file a great name then click on add then click on close you can see we actually have a raster layer here but if you look closely at the coordinates you'll notice that they are actually not right so we just want to assign coordinates to this raster layer so that it's now what is in its right place so we need a a plugin which is a core plugin called a geo reference app plugin so where do we find the geo refresher plugin it brings a call like a call plugin we're going to find it under raster so you select raster then you'll see at your referencer so we're going to select geofencer and it brings in a new window here so i'm going to just maximize it so that you can sit on this window and not looking at what is on the on the background and this new video it also has some tools here this file is edit this view that is settings the first thing we need to do is we need to bring our our jpeg file yeah and how do we bring it to this work area we click on the first tab here which is open raster i'm going to select the great name that is the wrestler actually download the token up it will bring it here now and then on this interface there is there this part here where the overview of whatever you are working on and then there is down here which there is some small box here called the tcp table the gcp table just the ground control points that you're going to be using to do your jio referencing they will be actually appearing here and for you to have a very very nice direct friendship you need to have at least three or more points in your in your in your map so that you have a nice reference we'll start by looking at these tools we have already used this tool here so you know how to open the raster then this is there start your referencing we're going to use this tool as soon as we have already done everything that you need to know map and we need to now run the analysis then there is these load gcps you can be having round code workflows and you want to load them you can also add you can also save the gcp points here then there is the add point this is what you are going to be using here you need to be adding control points on this raster layer here you can also delete the points you can also move the points these are tools you're going to be using the pen tool the zoom in and zoom out tool and all that the next thing we are going to look at is you're going to look at the settings that is very very important so under settings we're going to look at the transformation settings the transformation type we're going to leave it at linear the sampling method need nearly but actually so many things you can do here by trying to leave it to linear first then the crs you're going to leave it to the project crs which is the projection then the output raster we're just going to give it a new file in the same folder but it will have a title called modified and it's active file then compression we're not going to do any compression and we're going to save the gcp the ground control point and then we have you can actually generate reports if you want and the net pdf report on a pdf map but you're not interested in that right now and finally we're going to load our result into qgis these are the settings that i have and i'm going to click on ok to save them then now we want to now do our referencing what do we need for your referencing one we can actually get coordinates from our map here or we can get coordinates from our canvas or from any other kind of reference that we are going to be using but for this exercise we're going to just be using the context that are within our our raster layer so what i'm going to do is i'm going to zoom in so that i'm able to see the coordinates so i'm going to just zoom into one of the corners and you can see i can see very clearly there's some coordinates here and there on our grid if i pan like this you can see there's an another coordinate here and if i pan vertically you can see i have coordinate here i have another coordinate here so we have latitudes and longitudes and the rule of thea is where the latitude and longitude is up point a coordinate point so like for example this is a like this is a latitude and this is a longitude the planes moving from north to south and longitudes and points moving from east to western west or east are like larger tubes this is a latitude and this is a longitude so our first point should be where they intersect here and for me to be able to get this i need to get the first coordinate which is up here which is the longitude which is 31. so in my mind i know that i have that one it might be having so many figures but for now this is just simply just 31 degrees we're going to use 31 for the longitude and then for the y-axis or the latitude we're going to use 19. so i'm just going to go to this zoom to it nicely and then i'll come back to my tools here remember 31 and 19 i'm just going to select add a control a ground control point add a gcp at a point so i'm going to add this first point here and the x is 31 and the y is 19. up here you can see you can enter x y coordinates decent degrees milliseconds decimal degrees or predicted coordinates which is in meters which corresponds to the selected point or the image or alternative again just click on that pencil and be able to get there condensed directly from the canvas so you're not actually getting any coordinates from the canvas but you're just getting getting coordinates from whatever we see on our map the intersection of the two points is 31 and 90 for our part so for our first ground control point you're going to be using 31.19 i'm going to click on ok you can see a red dot appears there it means our first drum control point has been put you can see it is also down here so i'm going to zoom out this and then i'll look for another region it should be actually proportional so i'm going to select maybe somewhere down here so i'm just going to look at the coordinates you can see i zoom here now this region here you'll see there's 17 degrees and there is 16 degrees and there is that that's like 21 degrees and 42 degrees so i'm interested in in an intersection and you can see these two are intersecting here so it means that's our second ground control point can be put there the longitude which is the x is 31 the latitude which is the y is 17 so i'll zoom in 31 and 17 i'll zoom in this is where they meet i'll select that put it there and if 31 and 17 and again i just say okay because i'm not using anything from the canvas and say okay and i have my second ground control point let's look for one last point because we need at least three points and we said with proportionality is very important so i'm going to look for another point on this other side so i'm just going to pan and then zoom in to a region where i can get ground control point and you can see this is now the longitude is 35 degrees and i want to intersect with some latitude that is on these other sides the longitude is 35 here i'm going to just move down here and you can see i have 19 i'll not use 19 for now there is 18 here so where they intersect here is now our third ground control point so 35 and 18. 35 is the x and 18 is the y i'm going to just zoom in completely so that i'm i get the most precise point so 35 and 18 is somewhere here i'm going to click on the my yellow add point again and click on this and put 35 and 18 always make sure that you put the correct coordinates here because if you don't put the correct coordinates then you will have a wrong result so and then we click on okay so i have actually so far three points and i'm happy about the three points i am i'm satisfied i don't need to put many more points let's zoom out you can see my distribution of the points one point is here another point you see another point is here so the next step is to just perform there your referencing to perform the referencing i'm going to just click on this green play button here called the strategy referencing i'm going to click on it once it will tell you the progress and you can see and some few minutes you'll see the raster has been successfully referenced i'm just going to minimize this and i'm going now to my work area here remember we had only one file here and now we have two you can see now these are great nile modified and this was just a great knight i'm just going to zoom into the great nile modifier and you can see now i have a referenced scanned map so to know if it's your reference we can actually add a base map so that you can confirm if it was actually accurately jfs or we can just like look at the coordinates and you can see now the coordinates are very very much okay the coordinates are within that region actually so what i'm going to do is i'm going to add the bezel how do we add a baseline i'm going to use the head changes plugin and then i'm going to add a google satellite image and when i add a google satellite image actually it comes and covers everything so i'm going to just bring it below yes and now you can see our map is somewhere in the region of that so that you can actually see very clearly what is if this is really the exact location of where the map is supposed to be can actually do a little bit of modification let me just change the transparency of my great nail modified report it at say six nine or seventy i okay and now you can see actually there's a little bit of difference you can see this river coming here and then passing through here so i'll uncheck check so that you can actually confirm sorry and i uncheck you can see there is now the river on there then i check deliver on my map i can also do the same thing here you can see this is my map and then check them out you can see now the real river buses here so actually we have done excellent work on this during friendship now let's look at where our initial grade 9 was so what i'm going to do is i'm just going to zoom to everything and you will see now this was our great great name but now we have the rephrase that you can see it somewhere there so it has been actually placed in the right location let me just zoom in so that you can just see the difference you can see this was the great nail but now it's checked which was just pulled and put there in here in its right place now let's do for another example and see if it's going to actually work so what i'm going to do is i'm going to just remove the nail here remove the layer no longer need it thank you very much for that now we're going to do another geo referencing so i'm going to actually do the same thing go to raster your friends are then we're going to add now another image so i'm going to add an email maybe say that the map of sudan and we have a nice map here that was actually downloaded from the internet we want to perform the referencing to this and see if it's going to work nicely for us so remember the x is the longitude and the y is the latitude so where they meet is the coordinate so i'm going to just zoom in this and you can see the y is 10 degrees north and the x is 25 degrees east so where they meet is our meeting point so 25 degrees east x and 10 degrees not y so 25 and 10 so i'm going to add this point 25 and 10 okay why but i'm saying i'm going to say okay i'm also going to zoom out again then pan to another region maybe this one by the intersect again there is 25 and 20 north so 25 let me just zoom into that visible i'll zoom into this so it's 25 degrees eastern 20 degrees north so where the intersect is my my other next ground control point so 25 and 20. so i'm going to select this i'm going to say 25 and 20 i'm saying okay then i'm going to also do the same thing again i'm going to turn or maybe zoom out first then i'm going to look for another another point for proportionality you look for points that are a bit proportional so you can see there is 35 degrees east and there is 15 degrees north let's just follow this 35 degrees east 15 degrees north so that's our point at 5 and 15 where the intersect so it's 35 and i say okay i have three points i'm happy about i'm happy about them i'm going to actually run the geo refresher so i'm going to just click on and make sure the settings are okay transformation settings linear this is how we want it to be then okay then i'm going to just click on run and it has saved your reference successful the last has been refreshed so i'm going to look at my map and you can see it has already been added into our map i'm going to zoom out a bit and you can now see the sudan the map of sudan modified has been added onto our map i can even bring it down so that the grid line is up you can see the gridline is there and sudan map is nicely placed on its right location to confirm this you still use the best map and you see you can see if i if i zoom in here on the leg here you can see actually it is almost accurate you can see another also on the other side almost occurred so from this then on you can decide to get these information that you don't have like for example you can digitize the roads you can get the points like the airports you can actually create new layers of the airport you don't if you don't have this data you can even create the the names of these towns maybe and put them in on your new map as a new data and also you can also use these to actually then digitize and see some new information is within these and update your geodatabase so that's it you have performed your first geofencing if you found this video useful and you want to learn more in qgis subscribe to my channel hit the bell icon so that you can get a notification when i upload the next lesson otherwise i'm just happy you're here don't forget to give this video a thumbs up see you in the next lesson [Music] you

Channel: WiseGIS

Views: 565

Keywords: qgis, qgis 3.14, opendata, opensourcesoftware, foss, topographic map, georeferencer, georeferencing, georeference, sudan, topomaps, movavi, movavi video editor, google earth pro, qgis3, qgis 3, qgis tutorial, big data, open data, remote sensing, plug in, plugin, how to georeference

Id: UYZ25pXceC8

Length: 21min 22sec (1282 seconds)

Published: Thu Aug 27 2020