Scene-agnostic ALS boresight self-calibration

2026-06-22

AI Summary

This study addresses the limitations of conventional airborne laser scanning (ALS) systems, which rely on structured scenes and specific flight patterns for boresight calibration, rendering them unsuitable for routine mapping missions. To overcome this, the authors propose a scene-agnostic self-calibration method that replaces traditional planar constraints with automatically extracted point-to-point correspondences between overlapping strips, thereby eliminating dependence on terrain geometry and flight trajectory. The approach integrates raw INS/GNSS observations into two complementary calibration frameworks: a lightweight formulation suited for tactical- or navigation-grade inertial systems, and a factor-graph-based implementation that excels when inertial errors are poorly observable. Experimental results demonstrate that high-precision boresight calibration can be achieved across diverse flight missions and five classes of inertial measurement units using only three to four overlapping strips.

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...

Problem

• ALS boresight calibration
• scene-agnostic
• overlapping strips
• routine mapping missions
• plane-based constraints

Innovation

• scene-agnostic
• boresight self-calibration
• point-to-point correspondences
• factor-graph optimization
• ALS strip overlap