Good Day Everyone...
I have a (more or less) a technical question as related to the Mav 2ED and the thermal camera.
Recently I am was trying to interpret thermal imagery of a building's roof.
Sunrise...sun not of roof yet...
Outside temp was approximately 40F...
I am approximately 75 feet above ground level / approximately 55 feet above building / a flat roof building...
I expect to see varying colors based on the roof's radiative temperature and the particular color palette I am using...
(Essentially the brighter the color, the warmer it is -- relatively speaking)...
Isotherm setting is off...
ROI set to 33%...
Gain set to auto...
Auto FFC is enabled...
Using the "Rainbow" pallet or the "Hot Spot", I see what I would expect. Varying colors based on how the roof was radiating in the cool morning.
Found varying hot spots (almost white) which suggest a "warmer / hotter" area(s) than orange or red 10 to 20 feet away.
Found varying insulated ductwork that is a deep shade of blue to almost black which suggests that this particular item was near to the current outside temp of 40F -- foil insulated duct and pipe.
All of which I would expect.
I enabled the "spot temperature" feature to take a spot temperature reading. I was curious to know how "warm" the roof is in varying spots.
I expected the roof to be warmer than the current outside temperature.
However, I received a spot temperature in the mid to upper 20's -- essentially below freezing on a cool day with the outside temp approximately 40.
The lowest temp was 39 or 38 during the night.
And to add "insult to injury", there is a roof-mounted temperature sensor located approximately 20 feet above the roof. I checked it and it read 38F / 39Fdurng my operation.
I do not understand. I would expect a spot temperature above the current outside temperature. It hasn't been below freezing for several days. The roof is "dry" -- no snow or rain recently.
Later at my desk, I held the Mav and aimed it at my forehead -- 96 and some change -- close enough. That suggests to me the sensor is probably ok?
Would someone be kind enough to explain why a roof's radiative temperature would be below freezing under this set of circumstances?
Thank You
===================================================================== JOHN TRACEY BENNETT – SIU / PSO Unmanned Aerial Vehicle Administrator FAA Certified sUAS / UAV Operator (active) Chief Engineering Draftsman CAD Systems / Archive Systems Coordinator
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