Mixing reference systems between camera and GPS

[travis_b]

Surveying with UAV. Camera utilizes WGS84 system coordinates. The GPS coordinates utilized in camera allow more efficient initial alignment.

GCP's then may be on a local coordinate system. If this is the case, is there a problem?

I have a project whereby the photos were input, alignment done initially, GCP's registered and thereafter uploaded the local coordinate GPS points of the GCPs. Result is a mess. Not sure why.

Any experience with similar issues?

Thanks in advance.

[Alexey Pasumansky]

Hello travis_b,

At the moment it is not possiblt to use coordinates of the reference points (for cameras and markers) in the different coordinate systems in the same chunk, so after you've placed markers (GCPs) and loaded their coordinates you need to uncheck cameras in the Reference pane and switch the coordinate system to the one used for the GCPs surveying.

NAD83, Zone 12 has EPSG code 6341, so you can search it by the code in the coordinate system selection dialog.

[travis_b]

Alexey - thanks for the response. Appreciate it. Not sure how you managed to figure out NAD83 was what I was looking for but needless to say I am impressed.

In addition, practically most of the surveyors, etc I have been working with prefer using Northing and Easting instead of lat/long. My understanding is that Photoscan will only work on the lat/long and the Northing/Easting is not an alternative. Is this correct?

Thanks again.

[Alexey Pasumansky]

Hello travis_b,

You've given a hint about the coordinate system in another thread.

As for the column labels for the coordinates, they are selected according to the coordinate system used. For WGS84 and geographic coordinate system it would be Lat and Long, for projected coordinate system Northing and Easting (or Southing and Westing for south-oriented systems). Local coordinates will have just X and Y.

[DoraZ]

Hi!
When I flew over an object with my DJI Phantom4 drone, camera coordinates were geographical (phi, lambda). Then I measured GCP points on the land with my GPS device, but in local system of our country (x,y coordinates). Now I am interested: how do I "transform" camera coordinates into markers coordinates?
I have a picture of a problem. I want my camera coordinates to be just like these in a red rectangle. Can anyone help me please?

[Alexey Pasumansky]

Hello DoraZ,

To transform the coordinates in the Reference pane from one system to another it is necessary to use Convert button on the toolbar in the Reference pane (providing that transformation between two coordinate systems is possible).

In the version 1.2 it should be performed before loading markers, since all coordinates in the Reference pane will be converted accordingly. So I can suggest to do the following:
- export markers to XML file using Tools Menu -> Export Markers option,
- remove all markers from the project,
- switch the coordinate system in the Reference pane settings dialog back to WGS84,
- use Convert button on the Reference pane and select desired coordinate system,
- import markers from the file back to the project.

But please note that altitude values written by DJI may be incorrect - by default PhotoScan expects height above ellipsoid for the coordinate systems, unless different vertical datum is used.

Also in case you are not going to use the camera position data anyhow (leave cameras unchecked in the Reference pane), you do not need to convert the coordinates, as coordinates of unchecked instances wouldn't be used.

[jkova96]

Hi Alexey and others,
 
Did this feature of "mixing coordinate systems" between camera and markers been solved in Agisoft Metashape 1.8?
I'm getting strange results and strange offsets from ground when applying these two.
Camera XYZ and orientations have big errors according to Agisoft Metashape processing report.
Drone, from which pictures have been captured, has georeferenced in mean error from measurement side - 2 - 4 cm but...in Agisoft Metashape I got staggering 1 - 2 meters...
Please tell me what I'm doing wrong...

THIS IS MY WORKFLOW...

1. SET COORDINATE SYSTEM FOR CAMERAS AND MARKERS (Image_01 in attachments)
2. IMPORTING PHOTOS (Workflow --> Add photos)
3. GEOTAGGING PHOTOS (in WGS 84 --> Image_02 in attachments )
4. ALIGN PHOTOS (Generic preselection, according to Processing report)
5. IMPORTING MARKERS AND SETTING COORDINATE SYSTEM FOR MARKERS (Image_03 in attachments)

My errors from Agisoft Metashape report is shown on picture Image_04 in attachments.

But at the end I got really Huge errors...

I can send you original files (csv file for cameras and markers)
Maybe I'm doing something wrong...I really don't know....something is not good anyway...
PLEASE HELP !!

[jkova96]

Hi Alexey,
I follow your advice which you gave to DoraZ...
But when I do that, I got "nan" errors both for camera and markers?
I really don't understand...Is there any tutorial for these things?
Thanks
Bye.
J.K.

[Alexey Pasumansky]

Hello jkova96,

Can you provide the screenshots of the Reference pane settings dialog and source values tab of coordinates for the cameras and markers in the Reference pane, after your workflow?

[jkova96]

Yeah, definitely I will do that.
Can you tell me where do you want to receive data?
Any email option, or do you want from me to contact Agisoft support?
I can share my project via Agisoft Cloud too.

By the way one of my colleague says that GCP and controls points have so so good values after optimizing cameras...but still there's, from my opinion TOO MUCH error from calculated drone data - I mean on cameras positions and orientations too.

Best regards

J.K.

[Alexey Pasumansky]

Hello jkova96,

You can share the project via Agisoft Cloud (if it is already uploaded) using share visa email option for support@agisoft.com. Or just send a download link via any convenient file transfer service to support email address.