Updated: Sep 11, 2018
The project calibration is typically an abbreviated version of the system calibration. Generally, you’ll fly this at the project base of operation (for example, the airport), at the project collection elevation, or on a series of cross flights flown over the project location before and/or after the project collection for a given mission. This helps reference all the flight lines together so that mismatches of the flight lines will be eliminated or minimized.
Most specifications require a relative accuracy of between 5 and 10 centimeters vertically. The relative accuracy is the relationship of all the points and flight lines within itself.
Young, James. LiDAR for Dummies. Hoboken: Wiley Publishing, Inc., 2011.