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LiDAR- Why Do We need it? Benefits of Having High Resolution LiDAR Data

September 16th, 2009GIS in The Rockies

Presented by: Jamie Young General Manager – LiDAR services

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LiDARLight Detection And Ranging

Aerial sensorCollects/scans data, either photons (reflected light) or laser pulses

Aerial GPS (Global Positioning System) Based on GPS satellite triangulation, measures the location of the aircraft up to 0.1 second.

IMU (Inertial Measurement Unit)Measures attitude (pitch/yaw/roll) of aircraft every .002 second.

Ground GPSMeasures the location of the aircraft up to 0.1 second relative to a known ground position

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LiDAR Collection Sensor for Your project

• Sensors • Optech• Leica• Toposys• Reigl

• Multi-pulse versus Single Pulse• Single Pulse =150khz• MPia–Multi-Pulse in air = 300khz

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• Standard LIDAR – 1.4m point spacing – 18.5 cm RMSEz, 1.0 m Horizontal

– General-use, Meets most needs for LiDAR-based DEM

• FEMA Compliant LIDAR – 1.4m point spacing– 18.5 cm RMSEz, 1.0m Horizontal

– FEMA Map Modernization specified product– Meets FEMA guidelines and specifications for LiDAR-based

DEM

• High Density LIDAR – 0.7m point spacing– 15 cm RMSEz, 0.5m Horizontal

– Special use, high accuracy and point concentrated data – Meets most needs for LiDAR-based DEM in very dense

vegetation and terrain constrained areas

• High Accuracy LiDAR – 0.7m or more Point spacing– 9.24 cm RMSEz, 0.5 Horizontal

– Supplemental 1 foot accuracy specifications– 50% overlap for very dense vegetation– Requires very good calibration: Keep overlap

Typical LiDAR ProductsStandard, FEMA, High Density

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Additional LiDAR products

• Data collection as required by client• Breaklines products• Contour products • Low Density Collection

– 2-4 meter point sample density

• Very High Density Collections– 20-40 points per meter

• 3-D Building extraction– 3-D Wire frames

– 3-D Building polygons

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Additional LiDAR products

• Clients requiring Additional Classification– Water

• Smooth water bodies

– Vegetation• Low

• Medium

• High

– Buildings• Points

• Foot prints

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Sanborn Developed Water Body Classification

Lake on 7.5 quad map

Lake before classification and elevation averaging

Lake after classification and elevation averaging

ARC surface model

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Roads 1.4 meter Density

Profile at 1.4 meter

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Road 0.7 Meter

Profile at 0.7 meter

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Road 0.3 Meter

Profile at 0.3 meter

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Best Practices

• Planning– relief– Vegetation– Application

• Collection– Calibration– Control– Check Points– Field verification

• Processing– Filtering– Manual editing– Smart editing

• QA/QC

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Accuracy Issues

Calibration – Process to help verify the Project Data

Relative Accuracy of the data is critical – should be able to achieve under 10cm RMSEz and most cases under 5 cm RMSEz Verification of LiDAR Data is critical Manufacture need to listen to LiDAR vendors concerns:

Hardware ErrorIntensity issues

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Checking CalibrationDZ ortho - GeoCue

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LiDAR Accuracy StandardsThings to Consider

Accuracy is dependent on:• Flying height• Sensor parameters

– Rep Rate– Scan Angle – 10 degree of scan angle?

– Scan frequency

• System accuracy • Terrain• Vegetation• Data processing

and more…!

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LiDAR Data Accuracy

•Data meets RMSEz and accuracy requirements•Data does not edge match

Why?

•Large Collections•Small Collections

What can we do?

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LiDAR Post-processing

• Development of Production Work Flow to facilitate large Volumes of data

• IT infrastructure to handle large volumes of data

• QC processes through out the workflow• Latest Filtering Processes and Software

packages to ensure the best product.• Manual Edit/QC on all Tiles – We look at

everything• Localized Filtered data based on

characteristics of data• Internal accuracy assessment on all

projects• Processes to deal with “Corn rowing”• GeoCue Work Flow• SC Stereo Pairs and Orthos to facilitate

editing process and breakline process

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LiDAR Software and ViewersProduction Software

• ESRI– ARCGIS®

– 3D Analyst™

• QCoherent – LP360

• Microstation– Terrasolid

– Terrascan

• Virtual Geomatics– New Bore site Total

• GeoCue• More…

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ROI

• I talked with several LiDAR Users Very difficult to get information….!!!!– estimates that their initial ROI is $1 spent = $4 to $5 return?What they do know is that they get their money backWhy?

• Much more detailed elevation model (NED)• Many uses and applications• Shelf Life• Find Things they did not see before

• Karst formations in Alaska• Sink Holes in Iowa• Archeological sites in Kansas

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What Else What clients have to say…

– Less expensive? – more economical than traditional surveying or Photogrammetry

– Faster data? much more detailed– Collection around the clock– No AT, orthorectification or mosaicing required– Reliable terrain data –penetrates canopy– Non-intrusive – no land access required for paneling or

surveying– More accurate then auto-correlation– Multiple uses

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What Else?

• Clear shortcomings in existing elevation data sets that make shareholders tasks impossible to complete

• LiDAR lifespan – Most states -10 years– FEMA -15 to 20 years

• Current elevation data does not meet business needs

• Consider different resolutions in different areas to get most money out of collection.

• Better, cheaper, faster?

• Remote assess to some regions a concern. Is it here?

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LiDAR Programs

• County Updates– Gwinnett County, Georgia –Every Year

– PIMA County, AZ – Every 2 years

• State Programs– Iowa

• Full state in 3 years

– South Carolina• Buy ups – Spec ups – additional products

– North Carolina• 1999-2002 – 2 to 5 meter data

• 2009-2011 – 1.4 meter

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What else?

• Consider including many agencies to spread the cost• Determine the best resolution for all• How do you prioritize collection?

– Population or money usually does this

• Set up a contracting vehicle or use an existing one

• Lastly- QA/QC cost to make sure your data is good

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LiDAR BLOGSubmit your LiDAR questions...

http://lidarblog.wordpress.com

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Thank You! and Questions

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