To process images in PhotoScan using control points, it is important for the image heights to be relative to the same vertical datum as the control points. Some drone models cannot determine their height relative to a vertical datum but can accurately determine their height above the takeoff location. If the takeoff elevation is known, ASP Suite – Adjust Heights will allow the user to add or subtract elevation from the image heights. A text file is created with Lat, Lon, and altitude which can then be imported into PhotoScan.
Adjust Heights is part of the AirGon Sensor Package (ASP).
1. Determine the height of the takeoff location. If the drone is launched near a control point, then the elevation of the control point can be used. (If control is in feet, convert to meters.)
2. Open the ASP suite and click Import Files. (Figure 1)
3. Click on the Add File or Add Folder button, navigate to the images. Click OK. The photo locations should now populate the window. Click OK. (Figure 2)
4. Click the Tools tab. Click on Adjust Photo Height. (Figure 3)
5. Adjust Photo Height will automatically populate the label and reported elevation of the ground photo. Double check and make sure that the correct photo was chosen. Enter the correct height for the takeoff location. The offset will be calculated automatically. Click OK. (Figure 4)
6. A notification window will appear, showing that the image.txt file was created successfully. This file will be imported into PhotoScan, after importing the original photos, to correct the photo heights. (Figure 5)