Messages

1

General / Re: Altitude used in Processing UAV (DJI Phantom 4 Pro)

« on: January 25, 2018, 05:05:41 AM »

But as far as the accuracy of the Photoscan output, does it matter that Photoscan is using Above Sea Level (ASL) instead of Above Ground Level (AGL) data as far as determining relative elevation changes in the terrain?  That's relative elevation between points in the property, not absolute elevation ASL measurements of the terrain.

From the 3D reconstruction point of view, I guess the relative elevation should be pretty good. I'm also kinda curious whether the GPS inaccuracy will affect the relative elevation.

2

General / Re: Altitude used in Processing UAV (DJI Phantom 4 Pro)

« on: January 25, 2018, 05:02:42 AM »

This is a joke.

DJI company intentionally saved a "error" height value in Exif information!

The height shown in DJI GO App is the vertical height of the aircraft relative to the take-off point.

The two Altitude value are completely different.

I think it's time somebody came forward and sued the dji.

I think this is more like a problem with the GPS. DJI drones are using the built-in GPS for location data and we all know it's very inaccurate, so that's why we need GCPs to calibrate the results.

3

General / Re: How To Dummy Down Exports? Reduce Points

« on: January 25, 2018, 04:58:46 AM »

Hi jazzyj,

I would also like to hear some insights from users on this topic.

What I would normally do is generate satisfactory DTM (trees and irrelevant objects removed), and then export it either as Geotiff (can be used as grid) or XYZ format. This exporting process allows you to drop the file size and number of points by setting a bigger spacing.

Also I would think if you go back and drop the quality setting of your dense point cloud generation it might affect the accuracy of your model.

Hope this helps!

Cheers,
Thomas