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Author Topic: Camera Position Accuracy Setting For PPK + GCP  (Read 3458 times)

jazzyj

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Camera Position Accuracy Setting For PPK + GCP
« on: April 28, 2020, 09:37:29 AM »
My photos are geotagged using PPK however I did not have accurate coordinates for the position of the base station.  So relative camera position accuracy is high but absolute world coordinate position accuracy is low - typical GPS (3m horizontal, 10-20m vertical)

I also have several GCPs (I was unable to set the base station on one of them) which I have accurate coordinates for.

Theoretically I would think the PPK generated camera positions would improve relative accuracy of the ground surface between GCPs, where the GCPs would correct the absolute positional accuracy. 

I see there is a setting for camera position and marker position accuracy. My question is, in this circumstance do I leave the camera position accuracy at the default 10m because that is for absolute position accuracy, or do I change it to something like 0.1m?  I'm assuming I leave it assuming that is absolute position accuracy.  But the model should still be more accurate using PPK as the error in the GPS coordinates between photos should not fluctuate that much as compared to non PPK?
« Last Edit: April 28, 2020, 09:48:01 AM by jazzyj »

Alexey Pasumansky

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Re: Camera Position Accuracy Setting For PPK + GCP
« Reply #1 on: April 28, 2020, 12:40:45 PM »
Hello jazzyj,

If the absolute accuracy of the camera locations is not good, then I suggest to leave the default accuracy value and rely on GCPs mainly.

However, in principle you can try a two-step georeferencing procedure:
1. before adding GCPs set camera accuracy to 10 cm, align cameras and optimize,
2. add GCPs, uncheck cameras in the Reference pane and press Update on the Reference pane toolbar (do not optimize).
But I'm not sure if it gives better result compared to only marker based georeferencing and optimization.
Best regards,
Alexey Pasumansky,
Agisoft LLC

jazzyj

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Re: Camera Position Accuracy Setting For PPK + GCP
« Reply #2 on: April 28, 2020, 08:22:25 PM »
If I already did the first methos (10m camera accuracy > aligned cameras > loaded and marked GCPs > optimize with GCP only)

If I try the GCP update method with higher camera accuracy I am assuming I basically need to start from the beginning and re-align all the GCP markers, then use Update instead of Optimize?

Alexey Pasumansky

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Re: Camera Position Accuracy Setting For PPK + GCP
« Reply #3 on: April 28, 2020, 08:26:48 PM »
Hello jazzyj,

For the first method you can partially re-use the existing information, I can suggest the following:
- export markers (via File Menu -> Export Markers command) to XML file,
- remove markers from the project,
- select all cameras and reset alignment for them,
- check all cameras in the Reference pane and define proper camera accuracy,
- run align selected for all cameras (or Align Photos with the "reset current alignment" option disabled),
- optimize alignment,
- import markers from XML via File Menu -> Import Markers,
- uncheck cameras (or modify accuracy),
- check on all markers and press update button on the Reference pane toolbar.
Best regards,
Alexey Pasumansky,
Agisoft LLC

wizprod

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Re: Camera Position Accuracy Setting For PPK + GCP
« Reply #4 on: May 02, 2020, 10:54:43 AM »
My photos are geotagged using PPK however I did not have accurate coordinates for the position of the base station.  So relative camera position accuracy is high but absolute world coordinate position accuracy is low - typical GPS (3m horizontal, 10-20m vertical)

I also have several GCPs (I was unable to set the base station on one of them) which I have accurate coordinates for.

Theoretically I would think the PPK generated camera positions would improve relative accuracy of the ground surface between GCPs, where the GCPs would correct the absolute positional accuracy. 

Your GNSS base position and coordinates need to be the same for your GCP's and your PPK for the camera's, otherwise you will have a constant inconsistency between the camera positions and the GCP positions.