Please select Into the mobile phone version | Continue to access the computer ver.
Possible Bug with Elevation EXIF tags? FW: 01.05.0600
302 3 2018-6-6
Uploading and Loding Picture ...(0/1)
o(^-^)o
DroneMapper
lvl.4
Flight distance : 6880 ft
United States
Offline



Hello DJI and P4 Pilots:

We are working with a client trying to build photogrammetric maps with our desktop software and noticed a possible issue with the latest Phantom 4 firmware and the GPS Elevation EXIF tags. It seems like the tags between images are duplicated and rounded (truncated). Has anyone else seen this issue with the latest firmware? The original flight was flown using Map Pilot and the actual data collection is good. (See attached image)

Capture.PNG

I've also attached a log of the GPS positions and elevation tags:

DJI_0002.JPG        -108.648323305556        39.1244638888889        1531.652
DJI_0003.JPG        -108.648303388889        39.1247776666667        1531.752
DJI_0004.JPG        -108.648292944444        39.124973                        1531.752
DJI_0005.JPG        -108.6482775                39.1252869722222        1531.952
DJI_0006.JPG        -108.648267111111        39.1254975555556        1531.952
DJI_0007.JPG        -108.648251444444        39.125813                        1531.852
DJI_0008.JPG        -108.648239888889        39.1260232222222        1531.852
DJI_0009.JPG        -108.648228277778        39.1262351111111        1531.752
DJI_0010.JPG        -108.648214444444        39.1265526111111        1531.752
DJI_0011.JPG        -108.648205                39.1267619722222        1531.852
DJI_0012.JPG        -108.64818925                39.1270793055556        1531.852
DJI_0013.JPG        -108.648178138889        39.1272889722222        1531.952
DJI_0014.JPG        -108.648167083333        39.1274998611111        1531.952
DJI_0015.JPG        -108.648151972222        39.1278179166667        1531.852
DJI_0016.JPG        -108.648147388889        39.1279220555556        1531.952


Gray orthomosaic preview without geo-reference:

preview.png

Each elevation EXIF tag should be different, not a duplicate or rounded to the previous tags value. This causes problems geo-referencing and running photogrammetry routines in most cases. Any ideas DJI?

Thanks,
JP

https://dronemapper.com
Capture.PNG
2018-6-6
Use props
Labroides
Captain
Flight distance : 9991457 ft
Australia
Offline

It seems like the tags between images are duplicated and rounded (truncated).
I can't see the "problem" you are asking about.
The elevation details that you've shown don't appear to be duplicated or rounded.
Three decimal places is all I get using older firmware and it's quite normal to get repeated heights showing for images.  

0.001 metre is definitely far in excess of the ability of the GPS to accurately measure altitude.
I doubt your numbers have been rounded down.

Here are sample of elevations for consecutive images from a recent photogrammetry flight of mine (with older firmware) to compare.
They all end in 93 because the unit measures in 0.01 metre increments.
  
502.293
502.293
502.193
502.193
502.193
502.093
502.093
502.093
502.193
502.093
501.993
501.893
502.093
502.093
502.093

Each elevation EXIF tag should be different, not a duplicate or rounded to the previous tags value. This causes problems geo-referencing and running photogrammetry routines in most cases.
If the GPS altitude data was accurate, you would expect the altitude data to all be very close ... maybe +/- 0.5 metre and many would show the same altitude.
Does the exif altitude really matter anyway?
There's so much random error in GPS altitude data that relying on it would cause all kinds of problems anyway.
Doesn't photogrammetry calculate actual heights by performing millions of triangulations on identified common points?
2018-6-6
Use props
KedDK
Captain
Flight distance : 1133038 ft
Denmark
Offline

I have given up finding both head and tail in the altitude information from the EXIF in my P4P, you can see my attempt to get it in this thread.
Unfortunately I do not trust either the barometer information as i have noticed this having a strange behavior too, can only hope it is the aircraft and that it will show up better after i have send it to DJI later today.
2018-6-7
Use props
DroneMapper
lvl.4
Flight distance : 6880 ft
United States
Offline

Thanks for the additional info and feedback.
2018-6-7
Use props
Advanced
You need to log in before you can reply Login | Register now

Credit Rules