Duet T processing thermal_ir values

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Hello,

I apologize if these are basic questions, this is my first time processing thermal images and I am struggling to find documentation. I am trying to process imagery taken from a Duet T rig and have downloaded and am using the template provided by SenseFly. I am not making any changes to the template and am following the directions on their page, but I am unsure about the results, as shown below

duetT_thermal_ir
duetT_thermal_ir1512×832 200 KB

In the Reflectance Map panel, it says Min = 0 and Max = 38.56. What do these numbers represent? This is a very large range and shouldn’t be the case for our data.

But then, in Index Map, the Min = -37.09 and Max is still 38.56. If I import the file into R or ArcGIS Pro, these are the Min and Max values I see as well.

When visualizing in Color Maps and Prescription, the Min = -4.89 and Max = 20.34. Why are these different from above? Also, this is quite a range and seems incorrect. If I unclamp the values, there seem to be holes in the data, which are where I believe the Min and Max -37 to 38 are.

Why am I getting these odd Min and Max values and is there a way to process the images to get an actual value? These areas are of interest as they are shaded and in direct sun.

Which values should I use and should I consider temperatures? Do I need to do a conversion? Why does the Color Maps and Prescription remove the odd Min and Max values?

Thank you for any help.

Paul

2

Hello,
The reflectance map provides the temperature reading as an output if you are using the thermal camera. As you are mapping a bigger area with multiple areas of interest the range you are getting is reasonable. But I am not sure why your temperature ranges to -37. This might mainly be due to the quality of the raw images.
The correct map to use is the index map or the reflectance map with the temperature range of -37.09 to 38.56. So, when you open it in the R or ArcGIS, you will have the temperature range from -37.09 to 38.56.
The reason you are getting unreliable data is mainly the result of bad raw images data which might have to do with camera quality.

3

Thanks Kapil. The raw images do show these odd values, so we will investigate the camera further.

Best,

Paul