Hi everyone,

We're analyzing Persistent Scatterer InSAR (PS-InSAR) data near a bridge and noticed some residual vertical misalignment when comparing PS elevations with GNSS station measurements.

We suspect the issue may be due to a mismatch in vertical datums:

• Our GNSS points are in ellipsoidal heights (WGS84)
• Our DSM/InSAR outputs use CGVD2013 orthometric heights

Has anyone dealt with this kind of mismatch before?

I believe we need to transform the GNSS heights to CGVD2013 to make a proper comparison, but I’m unsure of the best method or tool to do this.

Questions:

How can we accurately transform WGS84 ellipsoidal heights to CGVD2013 orthometric heights?

Is there a recommended tool, geoid model, or workflow (e.g., NRCan tools, GDAL, or QGIS plugin)?

Once transformed, what's the best way to validate whether the alignment improved should we check Z-differences over flat areas like bridge decks?

Any help or examples would be greatly appreciated!