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Author Topic: Error in GCP altitude  (Read 1858 times)

aophilly

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Error in GCP altitude
« on: February 20, 2017, 08:12:25 PM »
Hi everyone,
i've a project with this data available:
- 7 GCP measurements with GPS(Lat-Lon-Elevation in WGS 84) high accuracy
- Camera calibration file.xml
- 60 Photos form drone survey of a flat area (ground height about 211 m)

The goal of the project is to compare the estimation of the camera parameters (lat - Lon - altitude) with the one obtained from the drone telemetry.

The problem is that the altitude obtained from the estimation is really different from the one obtained from the telemetry (ground height + altimeter = camera altitude); this difference is approximately 10 meters.

If I try to change the parameters of the settings panel, the estimated value of the GCP is too different from the one measured and the surface results not flat, but this is not acceptable (survey in a flat  field).

Google Drive link: https://drive.google.com/open?id=0B4xQsdob-wezVEZQaFhYbzhCMzA

Someone can help me ?

Thanks in advance

Alexey Pasumansky

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Re: Error in GCP altitude
« Reply #1 on: February 20, 2017, 08:47:53 PM »
Hello aophilly,

I think that the main issue is caused by the fact that all the images are taken almost from the same camera position, instead of following common aerial survey paths.
Best regards,
Alexey Pasumansky,
Agisoft LLC

aophilly

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Re: Error in GCP altitude
« Reply #2 on: February 20, 2017, 09:19:26 PM »
Do you have any tips or suggestion to correct this error?

Alexey Pasumansky

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Re: Error in GCP altitude
« Reply #3 on: February 21, 2017, 01:35:00 PM »
Hello aophilly,

I think the best option is to re-shoot the data, taking the images from reasonably distance camera positions, but still keeping good overlap.

I think that one cannot expect any good results for images taken from almost the same camera position, due to very small stereobase distance, compared to the distance to surface of interest.
Best regards,
Alexey Pasumansky,
Agisoft LLC