Oval-Scanning Bathymetric LiDAR Internal Error Calibration

The patent segments the calibration process into two distinct parts: flight dynamic calibration for boresight misalignment error and a new pre-flight calibration method for internal errors. By dividing the calibration into separate stages with different methods, each type of error can be addressed appropriately without mixing calibration objectives, thus resolving the contradiction between comprehensive error correction and calibration complexity.

The patent introduces a pre-flight calibration procedure that must be performed before the actual flight measurement. This preliminary action calibrates the internal errors of the laser scanning system using a controlled laboratory environment with known reference targets, ensuring that internal errors are eliminated before field deployment, thereby improving overall measurement accuracy without relying solely on complex flight dynamic calibration.

The patent introduces a prism-free total station as an intermediary measurement device that works in conjunction with the airborne lidar system during calibration. This intermediary device provides highly accurate independent measurements of the same targets, enabling the detection and calibration of internal errors including ranging errors and structural errors that would otherwise be invisible to the lidar system itself.

The patent replaces traditional prism-based total station measurement with a prism-free total station that uses reflective properties of targets. This substitution allows for more flexible and accurate measurement of multiple targets without requiring physical prisms to be attached, enabling better characterization of the lidar system's internal errors while maintaining coordinate alignment calibration.

The patent segments the internal error calibration into three distinct sequential steps: laser ranging error calibration, collimation axis error calibration, and rotation angle error calibration. Each step focuses on a specific type of internal error using targeted measurements and calculations, which improves calibration accuracy by addressing each error source methodically rather than attempting to correct all errors simultaneously.

The patent performs preliminary measurements and data collection during the calibration setup phase, including capturing laser footprint positions and corresponding total station measurements for multiple targets. This preliminary action prepares all necessary data in advance, allowing the actual calibration calculations to proceed efficiently through the three sequential steps without requiring additional field time during the calibration execution phase.