Associating a LiDAR Point Cloud with its Trajectory Data

Trajectory data provides information about the scanner’s position while capturing the LiDAR point cloud. The scanner positions should be ordered chronologically in the file.

Note:    Some .e57 files include internal trajectory information and therefore do not require an external one.

Trajectory data can be imported in a tab delimited .trjt (text format) file that includes the following lines:

§  First line: Define the LiDAR version (Should always be 1.0)

#version=1.0

§  Second line: Define the LiDAR’s coordinate system in WKT format.

#wkt=……

Note:        The WKT information must be in a single line without any line breaks. You can use the Coordinate System Generator to generate a WKT string defining the required coordinate system. See "Coordinate System" in the "Basic Concepts" chapter for more information.

§  Third line (optional): Indicates a time offset that should be added to the GPS time field in each record (default is 0).

#timebase=

§  For each known scanner position, add a separate line with the scanner’s position (X, Y, Altitude) and the time the position was recorded (GPS Time) in tab delimited format. The scanner positions should be ordered chronologically.

[x coordinate] <TAB> [y coordinate] <TAB> [altitude] <TAB> [GPS time]

Note:        The GPS Time is the double floating point time tag value at which the scanner’s position was recorded. This data must be in the same units and offset as the time data in the LiDAR file.

Example:

#version=1.0

#wkt=GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]

#timebase=0

9.63390819201651 <TAB> 47.4233597051724 <TAB> 401.463806152344 <TAB> 583.161876711994

9.63390818337074 <TAB> 47.4233597019402 <TAB> 401.463793239556 <TAB> 583.161876711994

9.63390817652904 <TAB> 47.4233597069347 <TAB> 401.463349871528 <TAB> 583.161876711994

9.63390818337074 <TAB> 47.4233597019402 <TAB> 401.463407984571 <TAB> 583.160397257656

To associate a LiDAR file with its trajectory file:

§  In the Project Tree select the LiDARs group, and then in the LiDARs list, select the required LiDAR and type the trajectory file's path in the Trajectory Path field.