ALSM Data Collection Overview

1. ALSM Data Collection Overview Preliminary imagery from GeoEarthScope Northern California LiDAR project. Final data products will be freely available from www.earthscope.org in coming months.

2. Acknowledgements • NCALM • Ken Hudnut (USGS) • Mike Bevis (OSU)

3. EarthScope • Funded by NSF and conducted in partnership with the USGS and NASA • EarthScope Facility • Seismic observatory (USArray) • The San Andreas Fault Observatory at Depth (SAFOD) • Plate Boundary Observatory (PBO) “EarthScope is a bold undertaking to apply modern observational, analytical and telecommunications technologies to investigate the structure and evolution of the North American continent and the physical processes controlling earthquakes and volcanic eruptions.”

4. GeoEarthScope • Includes acquisition of aerial and satellite imagery and geochronology. • Part of the EarthScope Facility project funded by NSF (MREFC). • Managed at UNAVCO. • Assist with EarthScope instrument siting. • Examine strain field at different temporal/spatial scales than geodetic & seismic instrumentation. • Data will be freely available.

5. UNAVCO • UNAVCO is a membership-governed consortium that supports and promotes Earth science by advancing high-precision techniques for the measurement and understanding of deformation • UNAVCO is funded by NSF and NASA • UNAVCO Facility supports PI projects • UNAVCO is constructing the EarthScope PBO • UNAVCO manages GeoEarthScope • UNAVCO hosts WInSAR • UNAVCO is based in Boulder, CO, with five regional offices to construct PBO

6. LiDAR and UNAVCO • UNAVCO manages Airborne LiDAR (ALSM) acquisition projects for GeoEarthScope • UNAVCO Facility provides GPS equipment and engineering support for Airborne LiDAR (ALSM) projects • UNAVCO Facility acquiring pool of Tripod LiDAR (TLS) scanning instruments to support community projects

7. Airborne Laser Swath Mapping (ALSM) Data Collection

8. Airborne Laser Swath Mapping (ALSM) Laser scanner Inertial Measurement Unit (IMU) GPS

9. Surface Point Spacing User definable to provide necessary point pacing on the surface

10. ALSM and InSAR Comparisons of Techniques for measuring surfaces and detecting changes in surfaces* * Ball park numbers for typical applications

11. ALSM Data Collection Parameters (NCALM) • Aircraft: Cessna 337 Skymaster • Personnel • One pilot, one operator in plane • GPS ground crew (2 to 10+ people) • Scanner: Optech near-IR • PRF: 33-125 KHz • Flying height: 600 – 1,000m AGL • Flying speed: 120 mph • Swath overlap: 50% nominal • Ground truthing: GPS (campaign & CORS) • Navigation solution: KARS • Point spacing: sub-meter • Nominal Accuracy (on open hard and flat surface) • Vertical: 3 – 6 cm. • Horizontal: 20 – 30 cm.

12. Some ALSM Acquisition Issues • Target identification and prioritization • Defining collection scheme and data product requirements • Tradeoffs concerning resolution vs. coverage • GPS ground control requirements • End use: geomorphology, geodesy, etc. • Cost (B4 ~$500/sq.km., NoCal ~$400/sq.km., DV ~$300/sq.km.) • Will the data be useful to users 5+ years from now? • Seasonal constraints • “Leaf off”, snow, heat, etc. • Data volume…lots of TB’s…yikes! • Standard data products? • Distribution scheme?

13. Workflow • Project planning • Target I.D., LiDAR parameters, GPS parameters, flight lines, permits, etc. • Data collection • Flying and GPS deployments • GPS data processing and trajectory generation • Kinematic software (KARS, TRACK, etc.) • LiDAR range processing and XYZ point cloud generation • Proprietary software (at present) • Filtered and unfiltered (e.g. full return and bare earth models) • Surface generation • Software (Surfer, Arc, GLW, etc.) • Algorithms (tinning, kriging, etc.)

14. ALSM Error Sources • Position and orientation of aircraft (trajectory) • IMU accuracy • GPS accuracy: • absolute vs. relative reference frames • GPS ground control points • Laser pulse rate frequency (B4 = 70 KHz, NoCal = 70-125 KHz) • Swath overlap • Atmosphere (GPS: water vapor, ionosphere, solar storms, etc.) • Flying conditions due to wind, terrain, etc. • Pilot skill • Topography • Dense / low-lying vegetation • Processing methods • Many more, many yet to be identified…new field

15. Corduroy scan edge SURFER 0.5 m DEM from NCALM - standard product

16. Corduroy There are two types of ‘corduroy’ in B4 data type 1 - ‘scan angle artifact’ scanner reads higher going one direction than it does in the other type 2 - ‘vertical swath offset’ aircraft first pass is vertically mis-aligned with second pass within a given area The second type, at least, can be mitigated or eliminated by increasing the accuracy of our GPS/IMU trajectories

17. Corduroy - type 1 Scan artifact - at scan edge on dry lake one sees a pattern of up-down consistently; as mirror flips, height reads differently

18. Corduroy - type 2 scan edge The inner scan is consistently lower than the outer scan; this is a different source of ‘corduroy,’ the second type.

19. GPS Positioning for ALSM Bill Elliott, USGS Volunteer Mike Sartori and the NCALM crew 1 Hz GPS base station from UNAVCO pool Surveying the B4 aircraft to determine the relative positions of the GPS antenna, the LIDAR, the IMU and the orientation of these vectors relative to the axes of the aircract.

22. B4 Project: Swath and GPS Points

24. Future GeoES LiDAR Projects • Southern/eastern California • Intermountain Seismic Belt • Pacific Northwest • Alaska