Trajectory Processing Wizard

Requires an LP360 Drone license.

Generating the lidar point cloud and orthophoto from the source data requires that the data be correctly positioned using the trajectory of the drone.  This is a post-processed kinematic (PPK) solution accomplished using one of several GNSS post processing software engines fully integrated into LP360's Trajectory Processing Wizard on the Sensor tab of the LP360 ribbon to combine the GNSS observations, both base and in-air, with the angular and acceleration data recorded by the onboard inertial measurement unit (IMU) in the position and orientation system.

How to Create a Post-Processed Trajectory File

Input Settings Page

1. Check the Cycle section to validate the correct cycle name and raw position file are being referenced. If you are using the default folder structure, these should not need to be changed.

Enable Payload Profile

Override Mounting Parameters File

Processing Range

LP360 Drone will attempt to automatically set the start/end time for the sensor trajectory processing based on the kinematic motion of the sensor. This works in the vast majority of cases, however, there are times where the user may want to change the start time of processing due to a mismatch of when the sensor and base station observation started or GNSS issues with either the sensor or base station during the beginning or ending of the flight. If you are unsure about what time to change, look at your current Post Process Trajectory Report, or generate one with the QC-Only (Realtime) option, and use the charts to determine areas where you may want to exclude due to GNSS data quality issues.

2. Select the Processing Mode you want to use to calculate your positions. 

Compare the Processing Modes for post processing the sensor trajectory

Single Base: Single Base Positioning is a GNSS processing mode where a single dedicated base station is employed to provide differential corrections to the rover GNSS receiver. 

SmartBase: Applanix SMARTBase is a web service that uses existing ephemeris data from public base station infrastructure around the world to generate a virtual base station at your trajectory.

PP-RTX: PP-RTX (Post-Processed Real-Time Extended) is a GNSS processing mode that utilizes Trimble® CenterPoint™ RTX technology. It provides centimeter-level post-processed positioning accuracies without requiring local reference stations.

QC only (Realtime): If available for your system, use this mode for field checks to verify the quality of the rover data. Only available for Applanix based sensors.

3. You need to select which Run Location you intend to use for processing:

• If you intended to run using a local desktop copy of POSPac UAV or POSPac MMS, select Local. This will require a licensed copy of POSPac UAV or POSPac MMS installed on the processing machine. Local processing with a Classic/Owned TrueView sensor does not consume LP360 Points.
• If you want to use cloud-based processing, select Cloud and enter/verify your LP360 Online login information is correct.  All cloud-based processing is subscription-based and may use LP360 Points from your pool as presented in the cost estimate.

4. GNSS Settings

• Use all Constellations - Select this option to include all available GNSS constellations (e.g., GPS, GLONASS, Galileo, BeiDou) in the trajectory solution. Using multiple constellations generally improves positioning accuracy and reliability, especially in environments with partial satellite visibility.
• Use Only GPS Satellites - Enable this option to restrict processing to GPS satellites only. This can be useful when other constellations introduce inconsistencies or gaps in data quality, or when compatibility with specific workflows is required. Note that limiting to GPS may reduce redundancy and positioning robustness compared to multi-constellation solutions.

5. Review the Cycle Summary section. If using LP360 Points, an estimate for the job plus your current account balance will be shown.

6. Press Next.

Base Station Settings Page

1. Verify the path for the Base Station Observation File(s) is correct.  This is the observation file you downloaded from the base station and copied to the Cycle\System folder on the USB. It was automatically moved to your project folders during the import and project set-up.  If you did not copy the observation file to Cycle\System earlier, you will need to browse to it and select it now using the button.

LP360 reads the base station antenna model from the observation file to determine whether a valid NGS antenna calibration is available. If the antenna model is recognized, it is displayed normally. If the antenna model is missing, unknown, or no calibration exists, the antenna name is shown in red.

Hovering over a red antenna model displays a warning tooltip indicating that no antenna calibration was found and that APC‑to‑ARP offsets will not be applied if processing continues. In this case, LP360 will prompt for confirmation before trajectory processing proceeds.

For a detailed explanation of this warning, when it may be acceptable to proceed, and how to resolve missing antenna calibrations, see Troubleshooting: Missing Antenna Calibration.

2. Enter your base station information in the lower section and verify it is correct.  

• Use Computed using Trimble CenterPoint RTX to compute the base station location from the submitted base station file to obtain a coordinate for that survey nail/reference mark. Only available for Applanix based sensors.
  Learn more about using the Base Station Location Computed using Trimble CenterPoint RTX
• Use the Survey Nail Manager in the Base Station Location section middle of the dialog to Save your base station definition for future reference.  You can use the dropdown section to recall previously saved Survey Nail locations.

3. Press Next.

Note: A message appears on the page to indicate the distance from the Survey Nail to the
approximate location found in the base observation file header. If this distance is greater
than 10 meters, the message shows in red, and you should verify the information as displayed
in the Location is correct. Over 50m will typically fail when processing the sensor trajectory.
Values in between are okay if you have verified the survey nail location to be correct. 

Ephemeris Settings Page

Required for TrueNav and DJI sensors. Not available for Applanix and CHC based sensors.

LP360 will only present the Ephemeris Settings page when required for the underlying GNSS post processing engine in use for the sensor being processed. The Ephemeris Settings page is used to configure the download of ephemeris or alternative navigation files, as well as configure additional GNSS processing settings. LP360 will attempt to download the necessary ephemeris files when the download button is pressed by the user or during the processing of the submitted PPT job.

• Ephemeris Mode:
  • Post-Processed (Downloaded from Internet) – Downloads the available mixed or GPS only ephemeris, and daily broadcast navigation file from the internet.
  • Broadcast (Use Alternate Navigation File (i.e., *.25N), downloaded from the Base Station (No internet connection required) – Uses the base station broadcast navigation file. No internet connection required.

• Ephemeris Files
  • Select to process using All Constellations (default) or to process using GPS only. You may elect to use GPS only if you are having issues processing a successful solution as one of the other constellations may be causing issues. Toggling this selection will trigger Auto-Download to download the corresponding ephemeris files.
  • Displays and allows for browsing to the ephemeris (.sp3) and/or the alternative navigation file (*.25N, *_GN.rnx for GPS Only, or *.25P, *_MN.rnx for All constellations).
  • Alternatively, manually download ephemeris files from the listed FTP links:
    1. Ephemeris FTP Server
    2. Ephemeris FTP Server (Mixed)
    3. Broadcast FTP Server (Daily)
  • The auto-download of the ephemerides is done via a connection to gdc.cddis.eosdis.nasa.gov (198.118.242.43) on port 21 using FTP-SSL. Your organization may only have a limited port range open and available for use by the auto-download function causing the auto-download to fail. You can use the Auto-Download Ephemeris Port Settings to limit the port range used by the FTP-SSL secondary data channel to auto-download ephemeris using only TCP ports within the specified range instead of the default, which is to use any port in the 1023-65535 range. A less accurate alternative, but possibly suitable for your needs, process using the Broadcast Mode and provide the *.25N or *_GN.rnx (GPS Only) or *.25P or *_MN.rnx (All constellations) file from your base station.
• GNSS Processing Settings
  • Elevation Mask (deg) and SNR Mask (dB) - The elevation mask and/or SNR mask can be changed by selecting the drop-down menu. The elevation mask is used to filter satellites low on the horizon, which can cause interference and reduced accuracy. Usually, it is best to start with the elevation mask set at 15, and then raise or lower it, as necessary. Getting all Q1 is the correct result. This means that there is fixed (2cm or less) accuracy. If there are Q2 or Q5 sections of the trajectory solution, then it may be necessary to check for missing/incorrect files or adjust the elevation mask and reprocess. For more information regarding GNSS quality levels, see GNSS Quality Levels Explained.
• Convert Base Observation File to RINEX 3.0 – This option can be used to convert your base station to the preferred RINEX 3.0 format. We do not have a good handle on when that is necessary. We have found it to be a viable solution in one instance if you cannot get a fixed solution (Q1) and are only achieving a float solution (Q2), yet everything looks like it should be achieving a fixed solution. However, we have also seen the opposite, where it was necessary to process without doing this conversion of the base station to get a fixed solution. We do not have a definitive answer yet as to when one or the other should be used.

Review / Results Page

1. Review batch processing job estimates. When you are satisfied, select Submit to submit your Post Process Trajectory (PPT) job to the Job Manager .
2. The session will finish processing and when:
   • Ready - Press Complete Job the Job Manager to review the Trajectory Report and/or the Trajectory Plot , depending on the GNSS post processing engine used. This can be useful as a rapid check on the results.  The Position Errors RMS section of the report can provide an accuracy assessment.
   • Failed - Press the Troubleshoot Job button in the Job Manager to open the applicable knowledge base article pertaining to the failure reason with probable resolutions.
     • GNSS Quality Levels Explained
     • Troubleshooting: "Error: Project Status: EXECUTION_FAILED"
     • Troubleshooting: "Error: An unexpected error occurred running POSPacBatch.exe
     • Troubleshooting: Unable to Locate the *.PosT File Below the Folder
3. Press Close to dismiss the dialog.

Note: Note that running a post process trajectory (PPT) job does not create any new layers in your project. If you need to externally check that the output was created and added to your project data set, you can browse to the Cycle\POS folder of your project and verify a PostProcessedTraj.txt file was written here. There will also be a new subfolder named POSPac_YYMMDD_hhmmss for each job you run. These subfolders contain detailed logs and files related to trajectory processing and are useful for troubleshooting issues.