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Author Topic: Anybody have any tips for DEM building?  (Read 670 times)

ihb

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Anybody have any tips for DEM building?
« on: August 07, 2019, 09:56:20 PM »
Hi everybody!

I am trying to determine crop height by subtracting a digital surface model (DSM) from a previously-flown digital elevation model (DEM) using RTK ground-control points for accuracy. I am using a Micasense RedEdge MX as my camera, attached to a DJI Matrice 200. I fly at an altitude of 50 feet (50.24 meters).

I am not liking the consistency that I am getting; I fly weekly, and my height models differ from week to week. Are there any Agisoft Metashape settings I should change?

Here is what I currently work with:

-Double-overlap grid flight mapping pattern
-20 RTK ground-control points
-Tie point limit: 60K
-Sparse point cloud alignment accuracy: High
-No gradual selection procedure
-Dense point cloud alignment accuracy: High
-Depth filtering: Mild


Any help would be wonderful. Thanks everybody.

-IHB

metaMick

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Re: Anybody have any tips for DEM building?
« Reply #1 on: August 08, 2019, 03:05:57 PM »
To narrow things down, I would undertake 2 sets of flights on the same day and do the comparison using exactly the flight plan, same day, same GCPs and metashape settings. So the only variable is the images. I wonder what sort of discrepancies you will get and how the size of those discrepancies will compare with your week to week comparisons. I would ensure the imagery was being taken on a wind-free days.