scope:

The cloud height indicator (CHI) system specified herein will measure cloud height and provide digitized data to remote units which indicate cloud height in feet or meets. This data is used for pilot information during performance of National Airspace System Traffic Control. This equipment will automatically perform data generation, data conversion, transmission, and display. This eliminates the necessity for an observer to read cloud height from a chart or to estimate cloud height and then transmit to ATC personnel either verbally or in writing the value thus obtained.