Presentation on theme: "ALSM Data Collection Overview Preliminary imagery from GeoEarthScope Northern California LiDAR project. Final data products will be freely available from."— Presentation transcript:
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.
Acknowledgements NCALM Ken Hudnut (USGS) Mike Bevis (OSU)
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.”
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. GeoEarthScope
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
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
Airborne Laser Swath Mapping (ALSM) Data Collection
Surface Point Spacing User definable to provide necessary point pacing on the surface
ALSM and InSAR Comparisons of Techniques for measuring surfaces and detecting changes in surfaces* GPSInSARALSMTLS Sample Density 1 site/10 km 2 10,000 pixels/ km 2 1-10 hits/ m 2 1000 hits/ m 2 Position Precision 1-20 mm2-3 m5-15 cm0.6-5 cm Change Detection 1 mm1-2 cm10 cm1 cm Scale Global100 km10-100 Km1 km * Ball park numbers for typical applications
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. ALSM Data Collection Parameters (NCALM)
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?
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.)
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
SURFER 0.5 m DEM from NCALM - standard product scan edge 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
Scan artifact - at scan edge on dry lake one sees a pattern of up-down consistently; as mirror flips, height reads differently Corduroy - type 1
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.
GPS Positioning for ALSM Bill Elliott, USGS Volunteer 1 Hz GPS base station from UNAVCO pool Mike Sartori and the NCALM crew 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.
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