How to get a vex robot to consistently turn 180/90 degrees.?

I've tried using the gyro, and lowering the turn speed, but it is always a degree or two off. For my purposes, it needs to be pretty much perfect

?2016-02-10T18:25:26Z

Count motor revolutions via an encoder with an interrupt routine. Calculate the number required for a turn. Slow down when getting near the required count. At the right moment, apply motor braking. Wheels are important, as you don't need slippage. Possibly use an optical mouse to determine direction, or a magnetic direction sensor to verify long term accuracy.

?2016-02-11T05:14:27Z

No chance to the nearest degree - slippage on ground, etc. You have to correct afterward with independent measurement.

Philomel2016-02-10T18:44:12Z

Mapping routine.

leticia2016-09-18T14:49:00Z

I was asking myself about this too

Anonymous2016-09-20T00:46:58Z

it depends...