Evaluating the Correctness of Airborne Laser Scanning Data Heights Using Vehicle-Based RTK and VRS GPS Observations

In this study, we describe a system in which a GPS receiver mounted on the roof of a car is used to provide reference information to evaluate the elevation accuracy and georeferencing of airborne laser scanning (ALS) point clouds. The concept was evaluated in the Klaukkala test area where a number of roads were traversed to collect real-time kinematic data. Two test cases were evaluated, including one case using the real-time kinematic (RTK) method with a dedicated GPS base station at a known benchmark in the area and another case using the GNSSnet virtual reference station service (VRS). The utility of both GPS methods was confirmed. When all test data were included, the mean difference between ALS data and GPS-based observations was ？2.4 cm for both RTK and VRS GPS cases. The corresponding dispersions were ±4.5 cm and ±5.9 cm, respectively. In addition, our examination did not reveal the presence of any significant rotation between ALS and GPS data.