Vertical difference between Calibrated target location and surveyed position

Hi, I have been exploring Pix4Dmatic as an alternative to Pix4Dmapper when it comes to getting corrections from a Real Time Network (RTN) on our RTK enabled drone. We connected the drone to the RTN and collected the images. Once the mission was completed we then connected our Trimble R10 rover to the same RTN to tie a handful of targets. Within Pix4Dmatic I specified the datum information and completed the initial calibration of the collected images. When I bring in the tied targets and mark them within the images as check points the horizontal error from the calibrated position to the surveyed position has showed great result being approximately 0.1’. My problem is when it comes to the vertical. Vertically I am seeing approximately 2.5’ from the computed position to the surveyed position. I can confirm it is not a rod bust. I am not sure where this vertical shift is coming from. My goal is to obtain the best results possible without constraining to the collected targets for the vertical difference. Hopefully someone has an explanation and solution?

Thank you.

Hi jlitts,
Can you confirm what coordinate system your RTN is correcting on? Is it NAD83 (2011)? In addition, can you confirm what vertical coordinate system your RTK drone is using. Is it the GRS80 ellipsoid, EGM96, etc. And then are you entering that information as the image coordinate system?

We have the same issue. We are a surveying firm and own the Mavic 3 enterpise with RTK module. Using a Custom Network NTRIP RTK on the drone should bring the data in at 93m in Pix4d matic after calibrations without the need for GCPs. But this comes out almost 50m off. We are using the pix4d coordinate system of OSGB36 - ODN Height - geoid OSGM15 .
Any reason why this is happening ?

Hi ben77,

Welcome to the community!

It sounds like there is a mismatch somewhere in the coordinate reference systems selected, most specifically the vertical reference.

Can you please describe the workflow you are following especially as it relates to Coordinate reference systems. They all need to coordinate, inconsistencies can add errors such as these.

  • What reference is used for this custom NTRIP network
  • Can you confirm what vertical coordinate system your RTK drone is using, and the images are tagged with?
  • You are selecting OSGB36 - ODN Height - geoid OSGM15 for the project in PIX4Dmatic. Is it safe to assume you are using EPSG:7405 with the OSGM15 geoid?


HI I’m having exactly the same problem. Did you find a solution?

Hi, I’m having the exact same problem. I do not seem to have EPSG:7405 as an option for either the coordinate reference or the vertical height reference.
If i have been connected to the Trimble VRS network (rtcm3 corections) and am looking for OSGB output what coordinate reference options should I be using?

Hi Tim,

As my colleague Mike mentioned in a post above, can you please confirm that the horizontal and vertical coordinate systems for the images are set correctly and reflect the coordinate system used by your RTK drone to fill in the geotags?