If dude is right, then it especially makes sense if the measuring instrument in question has anything camera-like in its functions, because we often say "to shoot" when taking pictures (or when when filming).
On the other hand, "to shoot" can also mean to set off explosives, at least in mining, for example. Don't know if the work required for grading was that extreme in your case.
In my dictionary of scientific terms, definition 2 of "grade" is "a surface prepared for the support of rails, a road, or a conduit," and 3 is: "the elevation of the finished surface of an engineering project." (The first definition has it as a verb, "to prepare a roadway or other land surface of uniform slope.")