Community 3.3.6

[Antoin_os]

Hello,
I am wondering if there is a module in C3D for processing thermal images?
Cheers,
antóin

[Mark Thompson]

Hello Antóin,

We also process Thermal data during certain times of the year and one of the first feedback I got from the Simactive team was to use Radiometric Tiffs rather than our colorized Jpegs, because they did not contain any absolute temperature values, once we completed the conversion to Tiffs, we proceeded with the processing. One more thing to add, the DEM generated from these images (thermal) was very low resolution, as you may know, thermal imagery is pretty low resolution in nature, so we proceeded to use a DEM generated from a previous lidar scan we had... you can also use a DEM generated from an RGB flight if you have one. One last recommendation, when you are about to create the mosaic, disable the color balancing option, this will prevent the software from modifying important values...

I hope my experience helps you Antóin....

Regards,

Mark

[Antoin_os]

Hey Mark,
Thanks for the response. Yes, we collected thermal quite a bit, too. Okay, it is interesting that you converted the radiometric image to a TIFF. Thanks!

Towards temperature measurement accuracy, a trick we figured out to increase the accuracy is aluminum foil. I am not sure what sensor you use. If you are using an uncooled microbolometer (like a FLIR Tau 2, or Workswell), when used with a drone they can suffer from fair bit of thermal drift. Typically, these sensors are black. As they are black, they can absorb a significant amount of solar heat energy during the flight. As the sensor is measuring emissivity and works via a relation between electric resistance and temperature - this can muddy the relationship that is used for radiant temperature estimation. By using HVAC aluminum foil, we were able to significantly, reduce the error in the radiant temperature measurements. This is super nerdy, but I figure folk here may have use for it. The paper that details this is below; it is open source - the story is in the figures, really.

Thanks again for the response!
*a

https://doi.org/10.3390/rs14246356 (Limiting External Absorptivity of UAV-Based Uncooled Thermal Infrared Sensors Increases Water Temperature Measurement Accuracy, O'Sullivan and Kurylyk, 2022)

[Mark Thompson]

That a great tip Antoin. I was unaware of this factor, thanks for the information.

We've used several sensors in the past, recently I have been collecting with a DJI Mavic 3 Thermal, minor issues like with any platform, however really maneuverable for our inspection jobs. We rarely process mosaics from our thermal data as we mostly use the colorized JPEGs for our reports.