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Joint Airborne Lidar Bathymetry Technical Center of Expertise KGPS Challenges

Joint Airborne Lidar Bathymetry Technical Center of Expertise KGPS Challenges. Previous Support & Future Obstacles Jeff Lillycrop, Eddie Culpepper & Eddie Wiggins. Presentation Outline. Brief JALBTCX Overview Support for Mobile District International Operations Insufficient tidal model

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Joint Airborne Lidar Bathymetry Technical Center of Expertise KGPS Challenges

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  1. Joint Airborne Lidar BathymetryTechnical Center of ExpertiseKGPS Challenges Previous Support & Future Obstacles Jeff Lillycrop, Eddie Culpepper & Eddie Wiggins

  2. Presentation Outline • Brief JALBTCX Overview • Support for Mobile District International Operations • Insufficient tidal model • KGPS solution • USACE Coastal Mapping Mission • Requirements • Vertical control methods

  3. Joint Airborne Lidar Bathymetry Technical Center of Expertise May 19, 1998 • JALBTCX Mission: • Conduct coastal mapping and charting surveys in support of Partner requirements. • Continue development and evolution of lidar and complementary technologies for coastal mapping and charting.

  4. Joint Airborne Lidar Bathymetry Technical Center of Expertise Stennis International Airport New JALBTCX Location • April 2004 - Relocating to Stennis International Airport • All partners will be represented and contract support staff will be on-site

  5. Presentation Outline • Brief JALBTCX Overview • Support for Mobile District International Operations • Insufficient tidal model • KGPS solution • USACE Coastal Mapping Mission • RequirementsVertical control methods

  6. Dredge Contract Administration • Ecuador requested that USACE issue and administer dredging contract • Early quantity surveys were not repeatable • Challenged to determine a method to produce repeatable data referenced to chart datum

  7. Dredge Contract Administration • Project location: Estero Salado, Ecuador • Inadequate tide model to produce repeatable data • Tide station separation • Complexity of estuary • Geoid model too coarse to capture the detailed variability in this area United Nations, January 2004

  8. Estero Salado, Ecuador 9.7km 13.0km 18.5km • Establish control relative to ellipsoid • Relate each control point to MLWS • Determine the height, or offset, of MLWS relative to the ellipsoid • Create a grid, tied to the control points, that provides offsets for all locations within survey area

  9. Utilize Ellipsoid as Vertical Reference • INOCAR provided published ellipsoid heights for control points on top of structures • Tide datum referenced to platform on structures • Offset between ellipsoid and tide reference points taped Navigational ranges with MLWS reference points Recording gage at Posorja.

  10. Model Offsets Established • Model set up with offsets • Return trip to Ecuador to verify offsets and model through data collection

  11. Verification Survey

  12. Collect “stationary” data near control point for about 5 to 10 minutes • Boat over consistent bottom • Compare ZGPS with ZTide • Collect data along a planned line going away from and toward the control point • Water level changes during line collection • Overlap lines based on different control points

  13. Data Flow Real-time XYZ Base Station Vessel GPS Base Ashtech Z-Xtreme DGPS Trimble 5700 DGPS Trimble 5700 Sounding Data Echotrac MKII GPS Rover Ashtech Z-Xtreme Tides Office Post-Process for Z XY Tide Corrected Z XYZGPS XYZTide

  14. Sample Results • 78% ± 15cm • 63% ± 10cm

  15. Not an “Everyday” Solution

  16. Not an “Everyday” Solution

  17. Presentation Outline • Brief JALBTCX Overview • Support for Mobile District International Operations • Insufficient tidal model • KGPS solution • USACE Coastal Mapping Mission • Requirements • Vertical control methods

  18. Seamless Topographic and Bathymetric

  19. USACE Coastal Mapping Requirements 0 – 5 meters 5 – 15 meters 15 – 50 meters

  20. FY04 Coastal Mapping Requirements 0 – 5 meters 5 – 15 meters 15 – 50 meters Draft FY04 Interagency Plan

  21. Airborne Tool Necessary • King Air 200 • Collect 5m density, 230m swath, 180 knots • Cover up to 76.6km2/hr

  22. USACE Accuracy Requirements • Vertical Accuracy • Depths <15ft (~4.5m) ±1.0ft (~30cm) • Depths >15ft (~4.5m) ±2.0ft (~60cm) • Horizontal Accuracy • System Accuracy 16ft (5m) • Feature Location Accuracy • Planimetric features 10ft (3m) • Fixed Navigation Aids 10ft (3m) • Floating Navigation Aids 30ft (10m) All accuracy values at 95% confidence. USACE EM 1110-2-1003,1 Jan 01

  23. Vertical Datum • Tide Based • Areas with undefined datum (MLLW) • Discontinuity between tide zones • Ellipsoid Based • Consistent reference for raw data • Convert to NAVD88 using geoid model

  24. Control Options • Utilize CORS • Many sites operated by State of Florida are at 1sec sample rates • Other sites would need to be increased to 1sec • Ground based • 25 to 30 km baseline • Significant personnel impact

  25. Control Network Goal • Utilize long baseline carrier phase GPS methods to: • allow aircraft to collect in a regionally efficient manner • provide opportunity for redundancy • Vertical error < 15cm • Discussions with NASA to obtain their support service • Solicit long baseline experience from within this workshop group

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