2010 LiDAR Collection in West Virginia’s Coal Fields
West Virginia GIS ConferenceJune 9, 2010
AOC and future mining LiDAR
Slide 2
LiDAR collection specifications
• Horizontal postings: 1 meter
• Vertical accuracy: 15 centimeters
• Additional derived data products include:– ESRI elevation grid– Hillshade– 2 foot contours used in AML program– Intensity image useful in QCing LiDAR data
• ~ 2 TB of data before derived products
Slide 3
Slide 4
LiDAR Technology
LiDAR = Light Detection And Ranging•Capable of emitting 100,000 pulses per second at altitudes less than 1,100 meters•Day or night operation•Capable of collecting millions of elevation points per hour•All digital: no intermediate steps to generate digital XYZ•Rapid turnaround: Capable of processing within a week•Multiple returns per pulse •Airborne: Easy to mobilize and demobilize•Non-Intrusive: capable of accessing remote areas
Solid state Class IV laser
Swath width: Variable; 0 to 0.93 x altitude (m)
Horizontal Accuracy: 1/2000 x altitude
Elevation Accuracy: +/- 15 cm (or better)
Typical spot center spacing is from 0.5 m to 5.0 m
Slide 5
•Acquisition
NOAA
Processing
Product
Workflow
Slide 6
•Pulse rate frequency (PRF)•Scan frequency•Scan angle•Desired overlap•Altitude•Make sure above parameters yield an acceptable resolution
Flight Planning
Slide 7
• Pre-Flight– Check aviation weather– Review day’s mission with pilots and ground crew
• In Airplane– Check system– Power up– Communicate with ground control operator– Initialize GPS/IMU
• In Flight– Transit to project area– Begin collection– Constantly monitor conditions during collection– Keep flight log
• Post Flight– Final initialization on GPS/IMU– Power down– Retrieve removable hard drives for data decoding and processing
Acquisition Process
Slide 8
Two Topcon Hiper dual frequency static GPS receivers equipped w/ FC-100 controllers.
20 channel integrated GPS receiver
Signals Tracked – L1/L2 C/A Code and P
Code (dual frequency)
76 mb of Memory
Advanced Multipath Reduction
Logging Intervals of up to 20 times per second (20Hz)
Horizontal – 3mm + 0.5ppm
Vertical – 5mm + 0.5ppm
Cold Start - < 60 sec
Warm Start - < 10 sec
Reacquisition - < 1 sec
Ground Control
Slide 9
Ground GPS Requirements
• Base station must be within 30 km (18 miles) from airborne laser.
• Use dual frequency GPS receivers.• Use two highly accurate published geodetic control points
during airborne data collection to provide redundancy.• PDOP of 4 or less, optimal 3 or less.• Data collected from at least 6 satellites at 1 second
epochs.• Base stations must have a clear view of the sky with
limited mulitpath.
Ground Control
Slide 10
GPS Planning
Slide 11
SBET
Slide 12
ALTMStorage
DownloadHard Drive
QC Data
PosPac
Extract / Decode Laser Data File
Process GPS
ComputeLaser Points
Output Laser Points
Microstation
Raw Laser Data
IMUInformation
Processing Workflow
Slide 13
Calibration
Building an ICI (=isolated computing island)• Isolates one or more VERY high
performance computers from central IT C&C during VERY long compute jobs:– No pushes of server OS upgrades– … followed by the requisite reboots– Isolate from dependence for TIPS licenses
via pool of WVDEP licenses network outages
– Enough local storage to create a peer-to-peer within-the-room network
– UPS on each PC
Slide 14
PC specs• HP800 workstations with 64 bit OSes
super modular.
• Single quad core CPUs 5th fastest on the planet when we purchased the boxes
• 16 GB RAM & 6 TB each local storage
• 4 megapixel displays + CUDA card
• Isolated peer-2-peer network when working off the net
• Gigabit network connections for on Net
• Local licenses of all core apps Slide 15
Qcing LiDAR and LiDAR software
Slide 16
• QCing LiDAR deliverables– 2003 Statewide GCPs file– Multiple LiDAR datasets that overlap
difference grid calculation– Trimble R8 GNSS receivers for spot
checks– Outsource via FEMA monies
• Software 64 bit, use multicores– Virtual Geomatics– Applied Imagery’s Quick Terrain Modeler
WV CORS
The end
Slide 18