This manual will guide you through the patch test calibration procedure when using a Merlin LiDAR produced by Carlson.
The procedure can be used for other vessel mounted laser scanners.
The purpose of the patch test calibration for laser scanners is to determine the mount angles of the laser scanner, relative to the three axes of the local coordinate system of the vessel. These three figures are often referred to as the roll-, pitch- and heading mount angles.
Applying the angles in the software is crucial for a quality LiDAR survey in order to ensure proper overlap of consecutive surveys taken from different navigation lines.
This process needs to be done/redone each time the hardware (Merlin LiDAR or the IMU) mounting has been changed (eg moved at least one of them to a new location).
Once the calibration angles are calculated, the values can be re-used accordingly.
It is recommended that a patch test calibration should be done each time a different mounting angle and corresponding values are used.
This guide will follow the instructions from the Merlin System Calibration Manual, which is provided with the device, calibrating first the heading offset, then roll and pitch.
We recommend interfacing the laser scanner using PPS time synchronisation to account for latency.