Uncalibrated thermal images from Autel 640T


I recently did a mapping mission of a field using the Autel Evo II Dual 640T V3, which has both an RGB and thermal camera. The thermal camera has a smaller footprint, so flights were conducted so that there would be 80% front and side overlap for the thermal imagery. Conditions were normal at the site at the time of flying.

When producing a reflectance map for the thermal imagery in Pix4Dmapper, only 37% of the thermal images were shown as calibrated. Additionally, despite the RGB and thermal images being taken at the exact same time, the flight path for the thermal camera appears crooked in P4Dmapper. The RGB orthomosaic was generated perfectly.

Below are the quality reports for both projects. Does anyone know how to fix the issue with the thermal imagery?

09-29-23 Midville RGB_report.pdf (3.1 MB)
09-29-23 Midville thermal_report.pdf (1.9 MB)


The GCPs were evidently messing up the reflectance map. I attempted to re-process without the GCPs and using a 1/2 image scale and changing the point density from high to optimal. Here is the new quality report:
09-29-23 Midville thermal_report.pdf (1.4 MB)

The reflectance map was much improved, however there are some very splotchy sections. An example of this is in the image below comparing the top 2 rows with the bottom 2. Is there a way to fix this?

Because of the very low resolution of thermal imagery, we recommend having 90% overlap for both front and side. Anything lower most likely will not calibrate. I also looked at your quality report and you have very high camera optimization error. Please enable All Prior for the internal camera optimization.

Enabling all prior appears to have produced a similar result to the first example I tried. I am confused as to why there is a huge cluster of images that are calibrated in the middle and produce a clear reflectance map whereas near all cameras outside of that cluster are not. I am not seeing an obvious difference in terms of picture quality or content, as they are all of an agricultural field. Below is the quality report. Any further suggestions for calibrating these areas? Thanks!

09-29-23 Midville thermal_report.pdf (1.7 MB)


The issue has been solved. I followed this video and used the optimized camera parameters following the initial processing. The reflectance map looks perfect. Here is the final quality report:

09-29-23 Midville thermal_report.pdf (1.4 MB)