Vertical (z-axis) coordinate systems on images and gcp's

I was recently presented with images and gcp’s where the images and GCP’s don’t both use the same vertical coordinate system.

I see that Pix4D allows setting the vertical coordinate system for each.

And the output coordinate system is also selectable.

Can I assume that Pix4D will automatically do the reconciliation between these three possibly different coordinate systems? Are there any limitations or restrictions?

Also - is it possible to disregard the Z-axis values of GCP’s?

Many thanks!

Hi @joe.stroup

Yes, Pix4Dmapper allows for the setting of different vertical coordinate systems for your images, GCPs, and the output coordinate system. Here’s a detailed explanation based on the context provided:

  1. Automatic Reconciliation : PIX4Dmapper is designed to reconcile different coordinate systems during processing automatically. When you input GCPs with a specific vertical coordinate system, and if your images have different coordinate metadata, Pix4Dmapper will work to align these during the processing stage to ensure the output is georeferenced correctly.

  2. Limitations and Restrictions : There are some important considerations to keep in mind:

  • If the GCP coordinate system is arbitrary, the output coordinate system must also be arbitrary.
  • The GCP coordinate system needs to be geographically close to the output coordinate system, meaning they should cover the same area on Earth.
  • Compound and vertical coordinate systems are not supported by the software for defining the GCP or output coordinate system. If a .prj file has been used to define the GCP or output coordinate system, verify that the coordinate system is supported by the software.
  1. Disregarding Z-axis Values of GCPs : It is possible to disregard the Z-axis values of GCPs in PIX4Dmapper. If you choose to do this, the software will only utilize the X and Y coordinates latitude and longitude for georeferencing, and the elevation will not be taken into account. This can be done during the GCP input stage by omitting the Z values or setting them to a constant value if vertical accuracy is not a concern for your project.