Troubleshooting ERROR_BASE_POSITION_ERROR (CHCNav)

📌 Problem

When using PPK processing in SLAM Processing or Trajectory Processing of a Cycle from a CHCNav powered system, such as the TVGO, TV539 or TV540, the TGO or PPT job fails with, "ERROR_BASE_POSITION_ERROR" message.

🔍 Root Cause

The "ERROR_BASE_POSITION_ERROR" message indicates that the GNSS processing engine cannot establish a valid base reference for trajectory computation. This typically occurs when base station data is missing, misconfigured, or incompatible with rover logs (TVGO, TV539 or TV540). Below are common causes, quick checks, and corrective actions.

1. Missing or Invalid Base Coordinates
   • No absolute position provided for the base station.
   • Base log does not fully overlap rover collection time.
2. Datum/Epoch Mismatch
   • Base coordinates in one CRS/epoch (e.g., NAD83(2011) @ 2010.0) processed as another (e.g., WGS84).
   • Elevation mismatches due to wrong base location selection.
3. Incorrect Antenna Metadata
   • Antenna type or height missing or incorrect.
   • Phase center offsets not applied.
4. Constellation Issues
   • Poor satellite geometry or problematic constellation (e.g., Beidou).
   • Initialization in GNSS-compromised areas.
5. Clock / Sampling Interval Problems
   • Base log interval mismatch (prefer 1-second sampling).
   • Gaps in base data relative to rover logs.
6. Device or Firmware Faults
   • Corrupt storage or firmware anomalies causing incomplete logs.

✓ Quick Checks

• ✓ Base Files
  • Confirm log spans full rover time range.
  • Verify sampling interval (1s recommended).
  • Validate coordinates (absolute position, correct CRS/epoch, ellipsoidal height).
  • Check antenna type and height.
• ✓ Rover (TVGO / TV539 / TV540)
  • Ensure initialization in open sky with ≥20 satellites.
  • For TVGO, use loop closures and multiple passes in GNSS-challenged areas.
• ✓ Constellation Settings
  • Start with GPS + GLONASS + Galileo.
  • Disable Beidou if suspected issues persist.

✅ Probable Resolutions

1. Verify Base Station Settings in LP360
   • CRS
   • Epoch 
   • Antenna model
   • Height
2. Recompute Base Coordinates
   • Use OPUS or CORS data.
   • Import with correct epoch and height type.
3. Update Antenna Metadata
   • Set correct antenna model and ARP height.
   • Adjust phase center offsets if using substitute antennas.
4. Re-Initialize Rover
   • Collect data in open sky.
   • Perform multiple passes for SLAM + GNSS fusion.
5. Constellation Sanitation
   • Disable problematic constellations and reprocess.
6. Firmware & Storage Check
   • Update firmware.
   • Inspect logs for storage errors; RMA if needed.

📚 LP360 Workflow Notes

• For TVGO in poor GNSS conditions, consider SLAM-only processing tied to ground control points.
• Always confirm base station metadata before processing.
• Initialize TVGO in open sky with strong satellite geometry.
• Keep firmware updated and monitor logs for anomalies.

📬 Need Help?

If you're still stuck, please Contact Support for assistance.