AI summaryⓘ
The authors describe a new way to calibrate the alignment of airborne laser scanning devices without needing special flight patterns or specific ground features like flat planes. Instead, they use automatically found matching points from overlapping flight paths to adjust the system. They propose two methods: a simpler one using GPS and inertial system data, and a more complex approach that uses detailed sensor data in a dynamic model. Tests showed both methods work well during regular mapping flights, with the simpler method sufficient for higher quality sensors and the complex method better for noisier data. This approach makes calibration easier and more flexible in everyday mapping missions.
ALS boresight calibrationairborne laser scanning (ALS)inertial navigation system (INS)GNSSfactor graphtrajectory adjustmentoverlapping stripslaser vector observationsmapping geometrysensor calibration
Abstract
ALS boresight calibration has relied for two decades on dedicated flight patterns over structured scenes containing planar surfaces of varied aspect and slope. While reliable, this approach imposes constraints on the scene content and operations, which limits its applicability to boresight recovery within routine mapping missions. We present a practical approach that substantially relaxes these requirements by replacing plane-based constraints with scene-agnostic point-to-point correspondences extracted automatically from overlapping ALS strips. Two complementary formulations are proposed to estimate boresight with laser vector observations: (i) a simpler parametric adjustment utilizing INS/GNSS trajectory; (ii) a rigorous formulation treating GNSS and raw inertial data within an existing factor-graph, i.e. a dynamic network, where boresight is added as an additional parameter. Both formulations are evaluated across four operational ALS flights equipped with five inertial systems, covering a wide range of flight altitudes, overlap geometries, terrain types and inertial sensor classes. The analysis draws a clear boundary between the legacy plane-based conditioning that falls short outside the calibration scenario and the proposed formulations, which either recover or absorb boresight effects under conventional mapping geometry. Among them, the lightweight formulation is sufficient for boresight recovery using tactical and navigation grade inertial sensors, while the general factor-graph approach is clearly superior when the inertial sensor errors are less observable within an optimal smoother. This supports the hypothesis that, for INS/GNSS trajectory of sufficient quality, the boresight calibration can be performed without particular scene prerequisites during routine mapping operations using a minimum of 3-4 overlapping strips, with either proposed formulation...