How to Measure a SightSensor's Height?

When calibrating a SightLogix device in WebConfig, you are asked to input the device's height.  

This variable is always the height above the ground - not above sea level. 

The best way to measure sensor height is to use a tape rule and measure height from the ground to the lens. This will be the value entered for sensor height in the calibration dialog. 

Note as well that the two calibration points used in map based calibration must be on the ground, so height for Calibration Point 1 and Calibration Point 2 are always "0"