Follow-up of Monday’s Lab
Photoscan Workflow:
- Add Photos
- (Align Photos*)
- Insert/Locate ground control points
- Align Photos (again)
- Build Dense Cloud
- Build Mesh
- Build DEM
- Build Orthomosaic
- Export DEM and Ortho
Problem with GPS Altitude EXIF tag lab data set: Current Phantom 4 firmware populates the GPS Altitude tag with the GPS altitude – GPS altitude, as a rule of thumb, can exceed 3 to 4 times the horizontal error.
Solution: Use the relative barometric altitude (luckily, the aircraft stores this measure in the EXIF, too).
The greater the altitude, the lower the pressure. Over a short distance and period of time, this is considered a more-accurate measure of height above ground level (AGL).
EXIFTOOL
Useage Examples:
List all EXIF tags for photo DJI_0186.JPG
exiftool.exe -s -g DJI_0186.JPG
Print the Relative Altitude of the photo DJI_0186.JPG:
exiftool.exe -p $xmp:RelativeAltitude DJI_0186.JPG
Store the GPS Latitude, GPS Longitude, Relative Altitude of all photos beginning with "DJI" in a text file called headerinfo.txt:
exiftool.exe -T -FileName -GPSLatitude -GPSLongitude -xmp:RelativeAltitude DJI* > headerinfo.txt
Import this information into Photoscan
- Process in Excel
- Create a new Chunk, Import Photos, Import reference data from ‘Reference’ tab in Photoscan, …