![]() ![]() Save the changes to your QGIS project, you will continue from this point for the next lesson.The tools in TopoDOT 64bit (used in MicroStation CONNECT) are by default organized differently than TopoDOT 32bit (used in MicroStation V8i). Set the map transparency to 50% and compare it to the aerial image. Your map and this image should match quite well. To check that your data is properly georeferenced you can open the aerial image in the exercise_data\forestry folder, named rautjarvi_aerial.tif. Note that the raster seems to be slightly rotated, but that is simply because the data is KKJ / Finland zone 2 and your project is in ETRS89 / ETRS-TM35FIN. Now you can see the map in QGIS project as a georeferenced raster. ![]() Note that you named the file already as rautjarvi_georef.tif when you edited the Georeferencer settings.In the folder exercise_data\forestry\digitizing, name the file rautjarvi_.Once you are happy with your control points save your ground control points, in case that you will need them later, and you will: The error in pixels should not be higher than 10 pixels, if it is you should review the points you have digitized and the coordinates you have entered to find what the problem is. The error in pixels can be seen also in the GCP table in the dX and dY columns. With already three digitized ground control points you will be able to see the georeferencing error as a red line coming out of the points. You should end up with something similar to this: Digitize at least three more ground control points in the same way you did the first one. Try to get ground control points as far from each other as possible. Zoom out in the image and move to the right until you find other cross-hair, and estimate how many kilometres you have moved. You should be able to calculate the coordinates of those points in relation to the first one. Look for other cross-hairs in the black lines image, they are separated 1000 meters from each other both in North and East direction. The first coordinate for the georeferencing is now ready. In the Enter map coordinates dialogue write the coordinates that appear in the map (X: 2557000 and Y: 6786000).Select the Add point tool and click in the intersection of the cross-hairs (pan and zoom as needed).You will use this point as the first ground control point for the georeferencing your map. Zoom in to the left lower corner of the map and note that there is a cross-hair with a coordinate pair, x and y, that as mentioned before are in KKJ / Finland zone 2 CRS.You can use the zooming and panning tools as you usually do in QGIS to inspect the image in the Georeferencer’s window. The map contains several cross-hairs marking the coordinates in the map, we will use those to georeferenciate this image. Set the rest of parameters as shown below.Click the icon next to the Output raster box, go to the folder and create the folder exercise_data\forestry\digitizing and name the file as rautjarvi_georef.tif.Open Settings ‣ Transformation settings.Next you should define the transformation settings for georeferencing the map: When prompted find and select the KKJ / Finland zone 2 CRS, it is the CRS that was used in Finland back in 1994 when this map was created.Add the map image file, rautjarvi_map.tif, as the image to georeferenciate, File ‣ Open raster.Open the georeference tool, Raster ‣ Georeferencer ‣ Georeferencer.Activate the plugin using the plugin manager as you have done in previous modules. You will use the georeferencing plugin from QGIS, the plugin is already installed in QGIS. Save the QGIS project as map_digitizing.qgs. Make sure that Enable ‘on the fly’ CRS transformation is checked, since we will be working with old data that is another CRS. Open QGIS and set the project’s CRS to ETRS89 / ETRS-TM35FIN in Project ‣ Project Properties ‣ CRS, which is the currently used CRS in Finland. Follow Along: Georeferencing the scanned map ¶ ![]()
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