Import Sensor Trajectory Files

In TerraScan the Import files command is used to import raw sensor trajectories into TerraScan. During the import, sensor trajectory information is converted into TerraScan trajectory binary files (*.TRJ). The TerraScan trajectory format is a publicly available format and is described in the Programming Interface section of the TerraScan User Guide.

The input files must contain at least time-stamped position and, for most processing tasks, attitude information. The input files can be:

  • text files in one of the implemented ASCII formats, see Supported file formats
  • binary files from Applanix or Riegl software, see Supported file formats
  • text files in a user-defined file format, see File formats / User trajectory formats

During the import, the software assigns some attributes to the trajectories and can apply coordinate transformations and/or a time stamp format conversion. Most of the settings defined in the import process can be changed later for the converted trajectory files by using the Edit information command or commands from the Tools pulldown menu.

To import a raw trajectory:

  1. Select Import trajectories command from the File pulldown menu. This opens the Import trajectories dialog, a standard dialog for selecting files.
  2. Select the raw trajectory file(s) and click Done. The Import trajectories dialog opens.
  3. Define settings and click OK.

This imports the trajectory file(s) and stores them as TerraScan trajectory binary file(s) into the active trajectory directory. The name of a file is determined by the seconds values of the first and last position in a trajectory file separated by an underline character.

Setting: Effect:
File format File format of the input file(s). This is usually recognized automatically for implemented input formats.
Attitude format Format of the INS file. This is only active if Merge from GPS and INS command is used to import trajectory information.
First number Number assigned to the first trajectory file. If more than one file is imported, the files are numbered incrementally.
Group Group number assigned to trajectory file(s). Groups may indicate, for example, different flight sessions and can be used by TerraMatch processes.
Quality Quality attribute assigned to trajectory file(s). Quality may indicate, for example, the accuracy of trajectories and can be used for TerraMatch and TerraScan processes.
System Scanner system used for data collection. This may add lever arm corrections to trajectory positions and thus, effect the computation of the scanner location at the moment of measuring a laser point.
WGS84 Transformation from WGS84 coordinates to another projection system applied during the import. The list contains projection systems that are active in Coordinate transformations / Built-in projection systems, Coordinate transformations / US State Planes, and Coordinate transformations / User projection systems categories of TerraScan Settings. For more information see the CueTip – Coordinate Reprojections, Datum Transformations and Geoid Adjustments in TerraScan
Transform Transformation applied during the import. The list contains transformations defined in Coordinate transformations / Transformations category of TerraScan Settings.
Input time Format of time stamps in the raw trajectory file(s): GPS seconds-of-week, GPS standard time, Unix time, or GPS time.
Store time as Format of time stamps in the converted files: GPS seconds-of-week, GPS standard time, or GPS time. If the format is different from the Input time format, time stamps are converted.
Survey data Date when the trajectory data was captured. The format is day/ month/year (dd/mm/yyyy). This is required for the conversion of time stamps from GPS seconds-of-week to GPS standard time and is only active if Input time and Store time as are set accordingly.
Input angles Format of angle values in the raw trajectory file(s): Degrees, Radians, or TopEye radians. This is usually set automatically for implemented input formats.
Adjust heading If on, the software applies a meridian convergence correction to heading values. The correction is based on the projection system set for WGS84 or the coordinate transformation set for Transform.
Thin positions If on, intermediate positions are skipped as long as the trajectory accuracy stays within the given tolerances.
Xyz tolerance Maximum allowed locational change of the trajectory caused by thinning. This is only active if Thin positions is switched on.
Angle tolerance Maximum allowed angular change of the trajectory caused by thinning. This is only active if Thin positions is switched on.
Break at long gaps If on, the software splits the trajectory if there is a gap between consecutive trajectory positions that is longer than the given Gap value. The gap value is given in seconds.

TerraScan and TerraMatch do not need highly accurate trajectory information. It is beneficial to remove unnecessary positions with Thin positions setting when importing a raw trajectory. This reduces the amount of memory consumed by the trajectory information and speeds up processes.

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