Trajectory Report Review for TrueView 3DIS (Applanix)

Requires an LP360 EVO Explorer or LP360 Drone license.

Applies to Cycles acquired using a TrueView 3DIS with an Applanix APX POS.

Once the sensor Trajectory Processing has completed, you will be prompted to view the Post Process Trajectory Report. Select Yes to view the Report, or No to move to the next step. You may reopen the report at any time by selecting Trajectory Report on the Sensor tab of the ribbon. There are several plots that one should review to ensure a viable trajectory solution before moving on to additional processing steps:

1. Rover Data Summary
   • Start/End time meets expectations.
   • Start of fine alignment is within a minute or two of takeoff. If it is exceedingly long, it may be due to a known POSPac v8.5 bug resolved in v8.6 that is clipping the ephemeris from the beginning of the Cycle. The issue can be worked around by adjusting the POSPac Processing Offset (LP360 -> File -> Project Settings -> EXP -> True View Experimental Settings) (Figure 1) value to a larger number (Default = 30s). Suggested to use 3600 or 7200 if there is an issue.

Figure 1: POSPac Processing Offset on Project Settings EXP Tab

2. Rover Data QC
   1. Primary Observables & Satellite Data
      1. GPS/GLONASS L2 Satellite Lock/Elevation
         1. Review this plot to ensure ephemeris information is available for all satellites for the entire length of the Cycle. If missing ephemeris information for any portion of the Cycle for satellite(s), there is a known POSPac v8.5 bug resolved in v8.6 that can be worked around by adjusting the POSPac Processing Offset (LP360 -> File -> Project Settings -> EXP -> True View Experimental Settings) (Figure 1) value to a larger number (Default = 30s). Suggested to use 3600 or 7200 if there is an issue.
         2. Review this plot to ensure there are not many cycle slips or data gaps throughout the Cycle.
      2. GPS, GLONASS, BEIDOU, GALILEO L2 SNR
         1. Review this plot for gaps or less than four satellites above 30°.

For mobile mapping, it is not unexpected to see significant cycle slips throughout the cycle if there are obstacles near the vehicle during the drive. It's important to look at the timing of the slips/gaps to determine if these are appropriate for specific sections of the drive.

3. Base Station Data QC
   1. Base Observables & Satellite Data
      1. Base GPS/GLONASS L2 Satellite Lock/Elevation
         1. Review this plot to ensure ephemeris information is available for all satellites for the entire length of the Cycle. 
         2. Review this plot to ensure there are not many cycle slips or data gaps throughout the Cycle.
      2. Base GPS, GLONASS, BEIDOU, GALILEO L2 SNR
         1. Review this plot for gaps or less than four satellites above 30°.
         2. If the plot is empty and you converted the manufacturer's file to RINEX for processing, reconvert including the SNR information.
4. Smoothed Trajectory Information
   1. Top View
      • Review the path of the trajectory solution and compare to the flight plan and the Cycle position feature files created during the Cycle Import .
   2. Altitude
      • Review the profile path of the trajectory solution and compare to expectations
5. Base Station Information
   1. Ensure the base antenna manufacturer and model is properly read from the RINEX file. Fix in the RINEX file if it says Unknown. Learn more about troubleshooting a missing antenna calibration 
   2. Verify the correct antenna height was used.
   3. Verify the correct base station coordinate was used.
   4. The Frame, Epoch and Ellipsoid should match that of the survey nail. For instance, a point from an OPUS solution should be Frame: NAD83_2011, Epoch: 2010, Ellipsoid: GRS_1980
6. GNSS QC
   1. GNSS QC Statistics
   • Look for 100% fixed solution, minimum four satellites (preferably many more) and a maximum PDOP less than 3.

For mobile mapping, it is not uncommon to have significantly less than 100% fixed solution if obstacles are present during the drive. This can affect other stats having elevated values for the following referenced steps as well. It's important to look at the timing of these in the plots to determine if lack of a fixed solution and other values that might be elevated are appropriate for specific sections of the drive.

3. Forward/Reverse Separation
   • Ideal 1-2cm in Easting/Northing and less than 5cm in down for single base processing.
4. PDOP
   • Ideally well less than three across the board
5. GNSS-Inertial Processor Configuration
   • Verify the correct GNSS lever arm and mounting angles were used for your 3DIS and drone configuration.
6. Smoothed Performance Metrics
   1. Position Error RMS (m)
      • Ideal 1-2cm in Easting/Northing and less than 5cm in down for single base processing.
7. Forward Processed Solution Status
   1. Processing Mode
      • Should be zero (Fixed NL) across the board. May have some portion at the very end that loses lock.
8. Baseline Length
   • Shows the 3D distance between the base station and the sensor throughout the Cycle. Ensure it falls within the 30km expectation. Review the Base Station Location used for processing if it does not.

The results of this process will be corrected position and orientation, which will be saved in a file named PostProcessedTraj.txt located in the POS folder in the LP360 Project Folder.