How to georeference a satellite image in QGIS
The Georeferencer dialog box will appear:
2. Click the “Open raster” icon to add the satellite image.
Navigate to the image, select it, and click “Open”. The image will appear in the dialog box.
The next few steps might take some practice. Do not get discouraged if the process does not seem to work perfectly the first time!
3. Open Google Earth. In Google Earth, open a kml file of one of the data layers that you have opened in QGIS, you will see that I’ve used this point data with pretty yellow dots. If you don’t already have any data just create 3 points spaced around the map but ensure they fall on recognisable features….you’ll see why in a minute!
4. Now we will use Google Earth to help us identify the locations of several points on the image we wish to georeference. The Georeferencer tool will use this information to correctly place the image within our map.
Pick 3 or 4 points that are located near the edge of the screen. We will use points “17”, “8”, and “7”.
We’ll start with point “17”. Zoom in a little bit in Google Earth.
5. Now zoom in on the same area in the Georeferencer. To do that, use this tool to draw a box around the area:
Here’s what we now see in the Georeferencer:
6. Let’s get even closer for greater precision. Repeat steps 7 and 8 as many times as need, so that the Google Earth image and the image you are georeferencing are so enlarged that they become pixelated and you can see clearly the individual cells:
7. Now create a reference point in the Georeferencer that corresponds to point “17”. To add a point, click this icon:
Use the point in Google Earth as a reference. When you are confident that you have found the right spot in the image that you are georeferencing, click it. A new dialog box will appear.
8. You have two options for filling in the X and Y coordinates. You may copy and paste the coordinates from Google Earth (right click the point, and select “Properties”) or you may click the “From map canvas” icon, which allows you to click on the point that appears in the QGIS map. If you chose to copy and paste coordinates, remember that X = latitude and Y = longitude.
This is where your use of Google Earth pays off as you have a good Lat/Lon position to relate your image to!
Click “OK”. The point will appear in the image, and the bottom section of the Georeferencer tool will display some descriptive information.
9. Now zoom back out in QGIS and in Google Earth, and repeat steps 7 – 11 for at least two more points.
10. Almost done. We must now provide transformation settings. Click this icon:
When your settings match the settings in the image below, click “OK”. Notice that you will have to choose a location and a name for the new tif image that you are creating.
11. To finish the process, click this icon:
The Georeferencer will now create a new file (a tif image) in the folder you selected and it will also add the image to your map:
This image will never need to be georeferenced again. Every time you open the tif file (not the original file, which is still just an image) in QGIS, the satellite photo will appear in its correct location.