Sensors!

[daltore]

The short answer is there's no way to say for sure.

The long answer is there's a way, but it's really complicated. Basically, the amount of drift accumulated is very dependent on the code running the gyro. Gyros have different responses based on temperature, so some gyros contain internal thermometers that are also output to the microcontroller. Another factor is noise. If you have a gyro that communicates by serial (good luck finding one, I haven't seen any), it'll be more accurate than if you have a wire running around carrying an analog voltage that's varying. With the analog signal, you have to do averaging to get any kind of usable data, and when you average, you lose resolution. Since the cRIO has such a high data rate, you could probably get away with it a little more easily. Also, MEMS devices in general work by using capacitance between a central mass and an outer edge. If you have any static charge on your robot, it may or may not affect the gyro. Also, calibration of a gyro will not necessarily work if you move it to a different location on the robot, because overall capacitance will change, and may or may not affect the capacitive difference.