Georeferencing in QGIS 3 | burdGIS

I'm at plans today's video is part of an online course that I tutor for Oxford University I thought I'd put it on the YouTube channel just so that more people can access it and if you're interested in the Oxford course you can type into Google Oxford continuing education and GIS and if you google that you should see introducing mapping spatial data and GIS online if you go to that page you can see the course summary so if you'd like to book on this course please do it does run for 10 weeks and it's kind of self-paced but we do expect you to have each practical done by the end of the week you can see all the information on the side here so if you're interested in that please look it up and sign up any questions feel free to ask me [Music] Matt phones let's take a look at geo referencing in QGIS 3 I've got a blank project here and the first thing I'm going to do is bring in a base map so that we can have a look at our area of interest so if I go to view go to panels and go to browser and then scroll down to XY said tiles if you don't know how to get XYZ tiles loaded up don't worry about it I've got a video for that so just follow that and you'll be up to speed so I'll drop Bing Earth in here and there's the world fantastic now my area of interest is going to be white and woods today which is in Oxford and I do have a shared file that's in that area it's just a linear track that I recorded while I was there I'll add that in the only reason for adding this in is actually just to zoom to it so that I can find my area of interest and boom there it is okay so I can turn off that shapefile now and here's white and woods in all this glory now what I want to do next is add in the raster that is going to be G referenced so I will do that and there we have it at the end it's gonna ask me what CRS I would like now I'll just go back a bit here at elite and show you because I added in Bing virtual earth Bing virtual earth is a web layer it's in pseudo Mercator and so our project is gonna have is CRS set two three eight five seven pseudo Mercator reason for that being is that the first layer you bring in will set the project CRS for you so if we bring in the white an aerial photo it's going to ask what CRS we want for that and it'll be the same as a project it just defaults to that as we have no CRS for this layer at the moment if i zoom to this layer it's in the middle of nowhere in fact it's in the middle of the ocean and QGIS is having difficulty drawing it not surprising really because we have no way the world that is and that's the whole point of geo referencing so if we use our little shapefile just a zoom back to our area of interest then the next thing I need to do is make sure that I've got the geo referencing plug-in installed so check if we've got the plug-in installed I'll go up to plugins and manage and install plugins and if you just type up here gorf and you can see that geo reference if G Dell is available and in QGIS 3 this is now a cool plugin so you cannot install it I'm just going to put that checkmark next to it ok that's and close out now if you want to find the geo reference it it's quite logical it's a pin raster and you just go to geo-referencer click on that it opens up now I've been practicing this a little bit for this demo so my master is already loaded but it normally will open with a blank screen so I'm just going to go to open raster navigate to where my master is and open that again it's going to ask what coordinate reference system I'd like to use and I'll keep it the same as the base map 385 7 pseudo Mercator ok that so will be geo referencing this to 385 7 pseudo Mercator you can zoom in and out on this image and you can interrogate it look for some decent control points up here if we hang over these tools you can see we've got add points delete points or move GCP points now the GCP stands for ground control points and what were effectively doing is saying that this points on our rustic is going to be the same as whatever points on the map so I'm going to do this really rough and ready just to give you a demo we're going to start off up here in this kind of brown field banging the corner now normally unzoom going to get this a lot more precise but I just want to go quickly to show you how it works so I've clicked that and then it asked me where I would like to get the coordinates from and I'm going to get them from the map canvas so I can zoom in here follow that hedgerow up and I know that it's that corner there okay you really get to need a tat well whilst doing this the area of interest becomes much more interesting so I've got a road going over a railway here I'll do one on that as well go to the map canvas zoom out a bit where's my road rail cross over it is down here I just like being refresh there we go okay that's and what abnormally aim for is at least five points generally speaking the more points the better so long as they're accurate go from one on the roundabouts and what I try to aim for is one in each corner and one in the middle just get that point there and then we'll probably be over to the water body for the next one but I think yeah down here just on the edge of that from the map canvas find the same spots okay that and we just need one final point in the middle it's up to you how many points you do put in it's a bit of trial and error sometimes you might need to remove some control points you might need to redo them move them around whatever so I'll just go for this field delineation coming off the track and then going to the map canvas again it's not so clear on this one but that's going to do just for demo purposes I would be a lot less smart - in real life okay so now we've got my control points I've got five of them I'm gonna hit the start geo referencing button now the first time you press the start geo referencing button it will come up and ask you for some more info so I'm just going to okay that and we've got all these fun things that we can put in so I've been doing this like I said public practice runs so this is entered for me but you may need to add all of these we've got different transformation types I'm going to go with thin plates blind spend some time read up on these learn what the differences are between them but that's a bit beyond the scope of this video just know that there are different ways we can transform this there are also different resampling methods some of which may be familiar to you if you work with Rusty's before targets ers as I said I'm going to keep it three eight five seven just to match with our layout of the Bing Map and output raster I'm going to choose that to be wide mod okay that no compression thank you very much and I'm gonna load it into QGIS when it's finished so I'm gonna okay that when my mouth starts to work again there we go where is it why hasn't it geo-reference this because I need to press the star geo referencing button again and once I do that you can see the progress happening then it is done so I'm gonna close my geo referencing window I'm going to save my tcp points just in case I want to come back to this later on and I'm going to zoom out and have a look at how my picture is now you can see there's a little bit scoot and that's probably because this became this came from a different CRS to begin with it may have come from wgs84 is the most likely candidate or it might just be a wall to picture because that's the way that physics works so let's have a look we can kind of interrogate this and have a look how good our geo referencing has been so if we get rid of white and Maude it looks like it's pretty good and it looks like it might be an older image you can see here where Bing have got these kind of side roads come around it slightly that they were put in afterwards so working with an old image here but it looks relatively well geo-referenced not bad for a bit of a slapdash effort and that's how you can dereference with QGIS so thanks a lot for watching please don't forget to subscribe do hit the like button it really helps and leave a comment below I like to talk happy mapping

Channel: burdGIS

Views: 48,481

Keywords: burdGIS, GIS, mapping, geospatial, cartography, georeference, crs, raster, QGIS, QGIS3, gereffing, georeferencing, plugin, GCP, ground control point

Id: OS6jm81rr5s

Length: 10min 21sec (621 seconds)

Published: Tue Aug 14 2018