If the Kestrel reads “CAL CPS”, then you will need to calibrate the compass prior to using. To do so, press the center button when CAL CPS is on the screen. Spin and the number 30 will appear on the screen. Hold the Kestrel vertical and rest the bottom of the Kestrel on a table or your hand and rotate the Kestrel in place until the number reaches 0. You can spin the Kestrel in either direction but it is recommended not to spin too fast or you can get a bad calibration.