Does large variations in GSD screw up processing?


#1

I’ve read that for a large site where the topography has large changes in elevation, if you fly the same altitude AGL from the starting point, it can create issues in processing.

However, if you have a target GSD, and therefore a target altitude AGL, as long as you never exceed that altitude so that the variation in GSD will always be better GSD than the target, it would seem to me that shouldn’t cause any issue. The issue would be if the GSD was a lot worse than the target at certain points in the flight path. Or is the potential issue in processing just any big difference in GSD despite whether it better or worse resolution?

Example: I want to generate a topographic map (DEM/DSM) where I want the elevation measurements to be accurate within 12 inches. It is widely stated the elevation measurement are typically accurate within 3 times the GSD. So I need a GSD of 4inches/pixel. (In reality it will be better because that GSD allows for an altitude above 400ft). So if some of the photos have a GSD of 1inch/pixel because of high points on the site being surveyed, whereas others will be 4inch/pixel at the low points of the site, is that going to create a problem in processing?

If you increase the starting point number, the flight time decreases to the point the flight time is 0 at the last starting point. It would seem to me you want to get the


#2

Thanks Jeff for reaching out. The GSD is usually compiled as an average so there will be no major issues in processing. You can also break your map into multiple flights depending on the varying heights that need to be used to fly your plan. I would recommend using our “Overlap Optimizer” app located in our App Market.

Thanks!
Yusuf
@consultant