Abstract
Laser mapping has become quite popular in recent days due to its capability of providing information directly in three dimensions. A Terrestrial Laser Scanning (TLS) system operates by emitting and locating returned laser pulses. Locating the returned pulses requires knowing precisely for each laser pulse, the vehicle position (e.g. GPS), the attitude of the vehicle using Inertial Measurement Unit (lMU), the scanner angle when the laser pulse left the sensor, and the slant range to the surface for that pulse. One of the most critical sources of error in TLS or any other laser scanning system is the angular misalignment between the scanner and the IMU, which is called misalignment or boresight error. This error must be addressed before a TLS system can accurately produce data. The purpose of this research is to develop a method and identify the requirements for calculating the small misalignment angles between the laser scanner and the combined GPS/lMU solution for position and attitude. A mathematical model is developed in order to acquire the misalignment angles, using simulated data which consists of coordinates of target points, position of the scanner, rotation matrix of the IMU, and the product matrix (i. e. [LU., l1y, I1z]T) derived from the range and the MATLAB program which initially solves for the Projection Matrix using preset boresight angles (Rb). The equation is then rearranged to solve for the Rb as the goal is to obtain the same prearranged values that are initially used in the first part of the analysis. The calculation of the misalignment angles is considered to be successful as the prearranged Roll, Pitch, and Heading values are obtained after a few iteration, verifying that the mathematical model is sufficient for the purpose of calibrating the Terrestrial Laser Scanner.
Highlights
The past 20 years have seen an explosive growth in the demand for geo-spatial data
Other sensors cannot be fully geo-referenced by Global Positioning System (GPS) alone; such as pushbroom digital scanners, laser scanners and imaging radar systems, which are important in kinematic mapping applications (EI-Sheimy, 1999)
Based on the results of this study, it may be stated that the boresight mathematical model applied, is a successful and adequate method for calibration purposes of a Mobile Mapping System
Summary
The past 20 years have seen an explosive growth in the demand for geo-spatial data. This demand has numerous sources and takes many forms; the net effect is an ever-increasing need for data that is more accurate, has higher density, is produced more rapidly, and is acquired less expensively. Point-wise GPS data collection systems have become popular. These systems (similar to the traditional terrestrial surveys) still require each point of interest to be occupied, and they have not significantly reduced either the cost or time requirements of data collection. The use of GCPs often puts operational constraints on a specific flight mission. This situation changed fundamentally when GPS data were included in the block adjustment of aerial triangulation. The use of airborne GPS data made block triangulation entirely independent of GCPs. In principle. Other sensors cannot be fully geo-referenced by GPS alone; such as pushbroom digital scanners, laser scanners and imaging radar systems, which are important in kinematic mapping applications (EI-Sheimy, 1999)
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