It would be useful if my GCPs could be exported in the same CRS as my project output during processing or separately. We have images in WGS84, Survey GCP shots in WGS84 and the project is being process with a target output of a NAD83 State Plane CRS. We take all of our data produced by Pix4D and go into other applications for the next step in the workflow as well as for verification and validation. Ideally we would be able to open the ortho image/tiles and then import the GCPs with something like Civil 3D and make sure everything is as expected.
Hi David,
Thanks for the suggestion!
I’d like to better understand your need, so that we have a good picture of what should be improved.
Could you describe the next step(s) of your workflow in more detail? and maybe how you do it at the moment?
We have survey equipment that supplies survey data/GCPs locations in WGS84 or in NAD83 (HARN) State Plane CRS. Our customers often ask for data in NAD83 or WGS84 or on a specific vertical datum. We can easily set the project output and get the point cloud or orthos in the desired CRS.
We move data from Pix4D into architecture, engineering and construction software. Applications like Civil 3D, Revit or Trimble RealWorks. The the first thing we do after importing the data is import our GCPs and check survey shots to validate the point cloud or ortho matches up horizontally and vertically with the survey data or existing survey data. In the attached screen shot we have about 18 actual GCPs placed over 250 acres with a lot of topography changes. Our survey crew provides me with a lot of check points in addition to my GCPs.
So the challenge I have is when WGS84 survey data and my project output is a NAD83 State Plane CRS which means I have to go convert the GCP/Survey points to the output CRS to pull them into other software. The horizontal is not so bad to convert externally, but vertical datum transformations are a big more challenging. Ideally we could get a .txt output of what we imported in the GCP/MTP manager in the project output CRS so it matches the las and ortho files CRS.
Thanks for the explanation.
From my understanding, you use the GCPs in the third party software as a check to make sure that the results are correctly aligned. Except that at the moment the transformation from the GCP coordinate system to the output coordinate system of the GCPs is problematic i.e. not automatic and not as accurate (or tricky depending on the coordinate system). Please correct me if I misunderstood.
In Pix4D projects with GCPs, outputs take into account the input of the GCPs and the accuracy of the project can be checked in the quality report (among others). Why is the second check necessary? Can something happen to the outputs when imported to the third party software? or is it a way to make sure the accuracy of the project is as said in the quality report?
Looking forward to your feedback.
If the measuring instruments allow it, a workaround could be that your survey crew directly measures GCPs in the output coordinate system, so that no conversion is required. Do you think this is a feasible option?
Your understanding of the workflow is correct. The reason we double check is we are combining a number of data sources. Subsurface utility surveys, gis data into Civil 3D and other applications. We need to verify that everything is aligning as expected with a high confidence in accuracy. The reason for so many double checks, thats what licensed surveyors do. Check, double check and then have someone else check before signing and delivering products/data to our customers.
I would love to have all of the input for GCPs be adjusted to the project output CRS, but we are staying in the vendor calibrated configurations so we can guarantee the accuracy device collecting the data.
We do like to verify the data to ensure it matches the quality report, but its also for ensuring other data is also as accurate. For example, we often have government survey data for manhole covers. We rarely use manhole covers as GCPs however so we will get a check shot of a manhole cover to validate the ortho and government records for the manhole are lining up as expected. Its just one more check in the workflow to ensure accuracy when bringing in multiple sources of data.
Very interesting! Thank you for the insights David. I have reported your request to our Product Management. Feel free to add new posts if you have other suggestions.