what is linear thermography?

Answer 1

The study of temperature along a line.

There are linear thermography machines used to take remote readings. Normally they are used in factories to look inside the furnace and get the temperature reading, but you can buy one for your barbecue from Sharper Image.

Now I don't know where you heard this term from or how it applies, but if you take the word apart it is linear = line and thermography = graphing of temperatures.