Without GCPs to lock into the site coordinate system, the orthomosaics generated by Site Scan will be accurate to within feet. Once ground control is added, accuracy improves to within inches. Using Site Scan Manager, it is possible to quickly georeference orthomosaics using survey points on the ground. You can also take a look to Adding Ground Control Points (GCP’s) with Site Scan Manager.
To georeference your orthomosaic and Digital Elevation Model (DEM), follow the steps below.
1.Open your Project and navigate to the “Job Data” tab. Here, I’ve displayed the GCPs using the eye icon next to text. It is obvious that this orthomosaic is sitting several feet to the southeast of its correct position.
2. Click the “Georeference” button next to your orthomosaic in the “Job Data” tab. You will be taken to the georeferencing tool where all of your GCPs are displayed on top of your orthomosaic.
3. Click each GCP you would like to use and place it on the orthomosaic with a second click. The original will become slightly transparent. If you make a mistake, just click the modified location a second time. Once you are finished click “Georeference”.Note: Site Scan Manager will only georeference using the points you elect to use. In this example, I have 95 points, but choose to use only a dozen or so.
4. The orthomosaic is now georeferenced and ready for analysis and comparison with design and engineering overlays. Notice that the difference between the image below and the original. The DEM will be automatically georeferenced as well, so any contours generated from the new ortho will be accurate to within inches.