i have two DTMs and two DSMs created from LAS files......
first LAS files were created in autumn
second LAS were created in spring
when i compare elevations between DTM autumn and DTM spring.......differences are minimal, but to and fro are big differences, like -50 metres
same at DSMs..
what could have caused it? may it be caused by noise by scanning or even something else?
thank you so much
Sorry, I am not with you here.
When you say "differences are minimal, but to and fro are big differences, like -50 metres",
is this a difference between the surveys or a difference between the DEM (ground surface) and DSM (includes structures)?
Well 50m is a lot. Are these from 2 different survey companies?
There is a possibility that one has supplied ellipsoidal heights and the other geoidal.
Better get back to the supplier to check.
Did they use some local control for their ht measurements?