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Geolocation Problem: RMS error = 0m

Pix4Dmapper Pix4Dmapper Questions/Troubleshooting
#1

Hi,
I have a weird problem with Geolocation.
I’ve started a project with 2522 photos, then added 3 GCP’s and two CP (pointed them in Basic Editor) and later start Initial Processing.
After Step 1, P4D showed me Report where in Geolocation Details I can find an GCP errors about 0,00000…
In the Check Points section I can find errors in about 4-6 cm (X and Y) which are disturbingly inaccurate comparing to My other projects.
I’ve tried to add some MTP to it and reoptimize, but it didn’t change much.
Any ideas how to solve the problem? Maybe with GCP’s? Errors 0,00000…m are weird :stuck_out_tongue:

Chorazyce_report.pdf (136.6 KB)

#2

Hello,

The RMS value is zero due to the numbers and the distribution of the GCPs.The GCPs are too far from each other. I would suggest you add more GCPs and also mark more images.

#3

Hello, Thanks for respond. I don’t think the distribution of GCP’s is the problem. There is one GCP for every 1km, so it’s more than enough. About marking those on images, there are at least 5 marks on every photo, so this should be fine as well.

#4

A residual error cannot be calculated with only 3 points. You need at least 4 points to calculate a transformation error.

Three points will shift, rotate, and scale a dataset. Once you add a fourth point or more, residual errors can be calculated for the transformation.