Ortho Shift error

PIX4Dmatic
1

This fall flying season we switched to matic from mapper. One issue we have not been able to fix is a 2.2 foot shift in the ortho tiff. This is very odd as the point cloud is spot on.
The error is confirmed by creating vectors from the GCP actual location to target visible in the ortho photo.
The ortho rectification is very good as the vector standard deviation is virtually zero. 0.04 -0.06’.
This error has occurred in all projects this Fall and is a consistent error both distance and direction so… it is likely a datum shift error that is occurring in the ortho but not the point cloud.
Any suggestions would be appreciated.

2

Hello Timothy,

May I ask which coordinate systems are you using and how did you realize there is a sift of 2.2 foot in the orthomosaic?

Is there a quality report and log file of a project you could share with us?

Best,

3

Nikoleta,

Attached is the last quality report from the last project we did. I will answer your questions on the forum.

03403-12-21-quality_report.pdf (380 KB)

4

Sorry, first time on the forum.
We do all of our projects in the local state coordinate system however we had problems assigning that in Matic so we select “Arbitrary” which significantly simplified the GCP marking. The GCP coordinates uploaded however, are in the local state coordinate system. The final products produced through Matic and Survey are transferred to Autocad including the ortho photo. The same surveyed GCP coordinates are used and that is where the shift is found. As described previously. We know the point cloud is good by using vectors in Survey to define the location of GCP’s visible in the cloud as well as other items ground located. We then DXF those vectors into the same Autocad project and check the location against ground surveyed locations. This problem seems to be unique to the ortho.
We can easily move the ortho over in autocad so it has not been a deal breaker however this is not a consistent problem with other ortho photo’s we use. As some techs delete the Ortho when not need to free up resources and speed up autocad and then re-insert the ortho if needed later. if the GCP’s are not rechecked we have a problem.

5

Hello Timothy,

May I ask which command line are you using to import the orthomosaic? Is it with command line GEOREFIMG? Can you have a look at this article and let me know if this resolves the issue?

Best,

6

We use the Raster Design tools add-on, from Autodesk in Civil 3D. It is a much more comprehensive management tool for raster images. Both techniques will utilize the georeferencing information embedded in the Geotiff file to orient the image, so they should both result in the same issue.

7

Hi Timothy,

Thanks for your prompt response.
Can you please try to import the orthomosaic, with the GeoRefImg command? To download the command, please click here.

To import orthomosaic, as described in the article I shared with you:

  1. Drag and drop the orthomosaic onto the main view of AutoCAD.
  2. Message asking for an insert point, scale factor and rotation angle will appear, press Enter three times.
  3. Double-click on the main window to zoom in to the orthomosaic.
  4. In command line type GEOREFIMG and press Enter.
  5. Select orthomosaic and press Enter.
  6. Double-click on the main window to zoom in to the extents of orthomosaic.

Please let me know how it goes.

Best,