[joshvm]

This is actually an issue with thermal imaging cameras. Typically you'll get calibrated readings back in Kelvin, not in Celsius. Usually it's well documented by the camera manufacturer, but if you're providing an API to users you need to make them aware what the units are and make a decision on what you're going to return. For example this crops up if the sensor only provides counts which you need to convert into a temperature.

From a hardware perspective it makes sense to use K because you can encode the image directly using unsigned numbers plus some gain to allow for fractional measurements.