 Hello, this is Hans van der Krust, Senior Lecturer at IHE Delft Institute for Water Education. In this video I'm going to demonstrate image-to-image geo-referencing. I've made a video before on that topic, but in this video we are going to change some of the default settings of the geo-referencer GDAL plugin, which is a core plugin, in order to make it dock in the QGIS interface and also to synchronize the two windows when we take the coordinates. So let's first check if the geo-referencer GDAL plugin is activated. It's a core plugin, so you only need to check the box to have it, and then you'll find it under the raster menu under geo-referencer, which will open this new window, which is on top of your QGIS window. If we go to configure geo-referencer, we can change some of the settings. It's useful to show the IDs of the ground control points, and I also want to see the map units in meters, and not in pixels, and I want the geo-referencer to be docked, so that's what we see here now. It automatically docks to the bottom of the screen. I would like to have it on the side, so we will later have a reference image on the left side, and here I open the scant map on the right side in the geo-referencer window. I'm going to geo-reference using the quick map services plugin, and with the Google satellite. There it is. Now we need to find our location. We can use the geo-coding plugin. You'll also find it in the plugin manager. In my case, it's already installed, and then you can use this icon and type the name of something that you know in the area, which is Mount Marsy in this case, and then it puts the point on the map, and we can go closer to then see if we can recognize some features on the satellite image and on the map, and indeed those lakes, they look familiar. Yeah, that lake. Let's change the projection for project on the fly reprojection to the one that we need for our scan map, which will be an NAD UTM zone 18 North, and we keep the default transformation, and we do this because the coordinates that we'll take from the satellite image will be in the NAD UTM zone 18 North projection. So I see here a feature that we can recognize, hopefully on both images. So there's a dam. When I zoom in, I can find the dam here, and then I first need to set the transformation settings. You can do that through the menu or through that button, and I put it on linear first, and then a cubic resampling, I keep all the other defaults. I'm going to add point, click somewhere on the dam on the map, and then I choose from map canvas, need to move the window a bit, and then I click somewhere on the dam. The detail level of the satellite image, of course, much larger than of this topographical map. It fills in the coordinates, and there's our first point, which is point number zero, ID zero. Now for your ground control points, you need to choose stable features, features that don't change much in time. So these lakeshores are a bit difficult, although they have nice shapes that you can use, but that's your last resort. It's better to look at human-made features like dams, buildings, or bridges. This area is quite uninhabited, so it might be a bit difficult to find easy ground control points, but here we see some buildings, some shelters, so let's see if we can find those also on the satellite image. It's that lake. We zoom in a bit, see the big construction, and then one over there, and if I check the shapes a bit, then it's probably that building over there. Click somewhere in the building, and in the middle of the building on the satellite image, and the coordinates are added. Let's look for other ground control points. There might be a dam over there, and there is human construction, and there we find it also on the map. I'm going to add that point, and from the third point we see an estimate of the error with the red line, and it reports the mean error. Let's look for another point, and what's useful is after three points you can switch on link georeferencer to QGIS and link QGIS to georeferencer, and if these are switched on it will guess the location on both views. There's another dam there, and I want to see it on the satellite image. I'm going to switch on that button, and then I see where it is. Here's a bridge, also a useful thing that is stable in time normally, so it's important to have a good spread over the map with your ground control points. This one is normally not recommended, this meander, but we see that it has almost the same shape as in the past, so I think it's quite stabilized in this area, and because it's hard to find many points here, we are also going to use this one. At the bottom of the screen we see that the mean error is 72 meters, with the default setting it will show up in pixels, but now we have set it to meters. Here's another building that we can use, there's another dam, and we see this quite shifted in this part of the map, so it's good that we put a point there. See the red line is larger on this side of the map, seems to be another dam there, a bridge, another point is another building, so we got quite some spread now. The other area is a bit hard to find ground control points, but to increase the accuracy I switched to a polynomial one, and that looks more reasonable, we also have enough points to do that, so we are now at 20.7 meters, and we can check also how both views match, and that looks quite reasonable, so with those little legs. So let's transform, and there it is, so on the left side we now have the geo-referenced map, and when we use spacebar we can blink the map, and we can compare different parts and see how well it worked, we see also our original points there on the map, looks quite reasonable. Another nice way to compare the map with the satellite image is to use another plugin which is called the map swipe plugin, where I activate the map swipe tool, and I get this button when I activate it, it says active layer, small more c, so that means that it will show now both, if I zoom in to also work, we can compare very precisely two different layers, so we've geo-referenced the map using a satellite image, and we use the docking functionality of the geo-referencer plugin, I hope you like this video, please subscribe to my youtube channel if you like this video and you want to receive updates, if you want more free GIS materials please go to gisopencorsair.org