Drone2Map Thermal Orthomosaics

[TimGreg]

Hi,

I am trying to create a true thermal ortho from my data captured using the DJI H20T sensor. I have seen a post stating that, since last year, Drone2Map enables working with DJI thermal data, but the more I read on the internet and try things myself, the more confused I become.

Generally, one needs to transform RJPEG into TIFFs using Python code to obtain degrees Celsius, which I have successfully done (the min and max values of converted fiiles match those in the DJI Thermal Analysis Tool 3 viewer). For correct conversion, data about local relative air humidity, ambient temperature, and distance from the sensor is required. I imported the converted TIFFs into Drone2Map and tried to create a true ortho. A layer was created, but with completely random values.

Since I wasn't sure whether the software requires converted TIFFs or RJPEG files, I tried using the RJPEG files as well. Surprisingly, the layer "looked" correct, but the values didn’t, although they seemed more realistic. However, there’s no way the conversion could be right because there was no option to define the aforementioned ambient conditions inside of Drone2Map.

My question is: what exactly are the correct steps to create a true thermal ortho? Should I work with converted TIFFs or original files? What should I do with the correct files? I have seen that one can define K1, K2, K3, and other constants, but as far as I know, the H20T doesn't have those.

I hope my question is clear. Thank you very much in advance!

Best,
Tim

[CodyBenkelman]

Tim

Sorry this hasn't been answered yet.  You should be able to process the original RJPG files without conversion, although you're correct that we have not implemented any corrections for ambient conditions or distance to sensor.  I'd be curious to discuss your requirements.  (I sent you a direct message)

One detail to note, for DJI thermal sensors only, is software from DJI is required to perform the conversion from raw digital numbers (proportional to energy) to temperature units.  We don't install that software by default due to the security limitations I assume you've heard about. This doesn't impact geometric processing, so it's not required to run a project, but you won't get temperature units - I think that may be what you indicated above.

If you don't have the DJI download, check your MyEsri portal - let us know if you can't find it.  Also note you can choose Celsius or Fahrenheit but you have to make that choice before processing.

Cody B. 

[PaulHaverkamp]

Thanks for the information Cody. I had the same question about the calibration of the images. I have the DJI camera package loaded as well, but is there a way to set the distance, humidity, emissivity, and reflected temperature? I am mostly doing landscapes and want to know if I should use the Python script mentioned to convert the images before loading into D2M. Are there any plans to add options to set these values in the future?

Thanks again,

Paul