Some processing functions require the use of trajectory information in conjunction with the laser points and gps timing information. Strip matching in TerraMatch for example, requires trajectory information in order to work. Therefore, increasingly, trajectory information is being required with the delivery of lidar point data. This information can be provided in the form of the SBET or in text format. Some software will have the ability to read the SBET format file directly, while others may require manipulation of the text file in order to work with the trajectory information. Below, two examples are given of how to trajectory information in different formats into the TerraScan software.
Choose ‘Set Directory’ option and navigate to, or create new trajectory folder in working project file structure (
see diagram)
Open “Manage Trajectories” dialog, choose ‘import file’ and select the required SBET file.
Draw into design on Level: Trajectory
Create a bounding polygon surrounding only trajectory portions of interest to the project
Choose ‘Delete outside polygon’ to split the trajectories and remove the turnarounds – use the tiles or lidar extent as a guide
Optional – delete trajectory element drawn into design and re-draw split trajectories.
Optional - SAVE the trajectories as text files – click ‘Output positions’, use TYXZRPH format, files will be saved in Set Trajectory folder.
Choose TerraScan settings, ensure the txt file type is set so trajectory information can be received:
TYXZRPH – 7 columns of data
Place in the project trajectory folder the text version of the trajectory file (output from POS)
Open the file in Textpad and remove necessary columns so you are left with Time, Lat., Long., Ellipsoidal height, Roll, Pitch and Heading
Import the trajectory file into TerraScan , making sure to select the correct zone number
Continue from Step 3 above
