I have some UAV images, but unfortunately these images lost their longitude, latitude, elevation informations and POS informations.
I still used Pix4Dmapper software to process these images to derive DOM and DSM. But I found the DSM values are negative, and the range of the DSM value are from -22.2872 to -20.8671.
Now I have two questions, thanks to anyone who can give me the detail answers:
- The DSM values are negative. Can I say the unit of these DSM values was Metre?
- I want to know the reasons why the DSM values are negative? How does these negative DSM values been calculated in Pix4Dmapper? What is the principle of these calculation?
The following screenshots are about the DSM processing and its results.