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Obtaining LiDAR Data, Contracting Considerations

Obtaining LiDAR Data, Contracting Considerations. Kenny Legleiter Project Manager Merrick & Company. Cost Considerations. $$$$. How much will LiDAR Cost?. Factors that Affect Price. Contracting mechanism Writing of the specifications/statement of work

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Obtaining LiDAR Data, Contracting Considerations

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  1. Obtaining LiDAR Data, Contracting Considerations Kenny Legleiter Project Manager Merrick & Company

  2. Cost Considerations $$$$ How much will LiDAR Cost?

  3. Factors that Affect Price • Contracting mechanism • Writing of the specifications/statement of work • Entity doing the QA/QC of the data • Disk space needs • Client project management • Acquisition parameters • Acquisition sensors (LiDAR, Digital cameras, hyperspectral, thermal)

  4. Factors that Affect Price (cont.) • Square mileage of area (cheaper by the dozen) • Shape of the project area (square or rectangular in shape is best) • Ground Sample Distance (GSD) • <1 meter • 1 meter • 2 meter • 3 meter

  5. Factors that Affect Price (cont.) • Final Product Deliverables • LiDAR only processed to bare earth • LiDAR with breaklines • Contour intervals • Imagery / Digital Orthophotography • Map Accuracy Specifications • ASPRS – Class 1, 2 or 3 • National Standard for Spatial Data Accuracy (NSSDA) • FEMA • Number of QA/QC Points

  6. LIDAR Cost Examples

  7. Contracts/Agreements What factors should be considered when contracting for LiDAR?

  8. The Keys to a Successful LiDAR Project • Understand your mapping requirements and the purpose for completing a LIDAR project prior to signing of the contract. • Utilize a qualification-based selection process to select your LIDAR consultant. • Hire a LiDAR firm that owns a LIDAR sensor. • Ask for quality control plan. • Dedicate the appropriate number of internal resources to the project. • Determine who will lead the effort, act as a Project Manager

  9. Keys to a Successful LiDAR Project (continued) • Know exactly how the quality control is going to be performed by the consultant and internally. • Understand the differences in LIDAR technology. The age of the sensor, pulse rate, roll compensation, field of view are unique to each system. • Determine which accuracy specification is going to be adhered to (i.e. ASPRS, NMAS, NSSDA, etc.). • Hybrid accuracy standards should only be used as long as there is accurate LiDAR specifications and is tailored to the project.

  10. Keys to a Successful LiDAR Project (continued) • Include a ground truth survey component in the project. Best if completed independently of LiDAR contractor. • Request a LIDAR flight plan in the Request For Qualifications that clearly demonstrates the consultants understanding of the acquisition issues. (side overlap percentages, eye safety requirements, flight line breaks due to extreme elevation change, multiple pass areas over very tall buildings, etc.) • Make sure LiDAR specifications are in the RFP or RFQ, don’t use a traditional photogrammetry specification or use a LiDAR specifications that is several years old

  11. Three Types of Contracts • Request for Proposals (RFP) • Price key factor • Common for local governments • Request for Qualifications (RFQ) • Qualifications key factor • Price worked out after award • Indefinite Delivery/Indefinite Quantity (IDIQ) • Multiple task orders/multiple years • Ex. USGS, Corps of Engineers

  12. QA/QC of Data Exactly how accurate is my data? Allows users to understand “how accurate is accurate”

  13. Sources of Error in LiDAR Data • DGPS, Differential GPS • Position of the plane (lat, long, elevation) • IMU, Inertial Measurement Unit • Attitude of the plane (pitch, roll, heading) • LiDAR Sensor • Accuracy of ranging and trajectories of shots. • Calibration of data • Relative accuracy of data which is typically the greatest source of error. • Ground control survey • Control creates absolute accuracy. • System Installation • System mounting • Flight Acquisition • Proper GPS and IMU collection procedures • Data Processing Problems • GPS processing and LiDAR boresighting • Filtering • Smoothing

  14. Helpful Hints • How is the data going to be QA/QC once it is delivered – BE PREPARED!! • Each delivery should be reviewed and commented on within 30-days of delivery • Software can be used to help with QA/QC the land cover survey points – determine accuracy by land cover • Other review methods to look for artifacts, quality of data, data formatting, flight lines not aligned, etc. • Recommend hiring an experienced company to do the review (ex. Dewberry)

  15. Land Cover Validation Methods QA/QC using survey equipment • Individual check points • Surveyed cross sections • Area surveys • Existing survey points

  16. Ground Truth Surveying Require a digital photograph of the survey shot

  17. Land Cover Ground Truth Surveying • Detailed land-cover and land-use classification survey • Used to determine accuracy in and under vegetation • FEMA guidelines for cover class surveys • Allows users to understand “how accurate is accurate”

  18. Individual Checkpoints • FEMA has general guidelines, but each region of the country will be different • Urban • Bare ground • Short grass • Brush • Forest • 20 or more survey points per category, minimum of three land cover types

  19. Area Surveys and Cross-Sections • Verify larger area (compared to single points) • Typically high degree of accuracy • Provides an accuracy assessment for real world applications • High Cost

  20. Existing Control, UtilityContour Databases • Existing databases with elevations attributes(i.e., geodetic, utility surveys) • Depending on vintage, may not truly represent present conditions • Be careful of basis of survey methodology • Wrong projections/datums

  21. Survey Control Report • Works upon analyzing control point elevations compared to their vertical intersection point of the LiDAR TIN, depending on the user defined classes enabled and disabled • Only reports vertical accuracy • Contour Interval Wizard to choose from: • FGDC/NSSDA/FEMA • ASPRS Class 1, 2, or 3 • NMAS • RMSEz or Vertical Accuracy requirement can by manually input • Control is analyzed to TIN of DSM surface • Statistics report: • Average Z Error • Median Z Error • Minimum Z Error • Maximum Z Error • Standards report for PASS or FAIL for: • Average Z Error • RMSEz • Vertical Accuracy • Achievable Contour Interval report for: • FGDC/NSSDA/FEMA • ASPRS Class 1, 2, or 3 • NMAS • Selectable classes to analyze from • Tabular readout of all control information • Export control report to Excel file • Export DSM data for the 3 points forming the TIN of analysis for each control point

  22. Contour Results Contours with breaklines DTM Contours without breaklines DEM

  23. Visual Inspection Should NOT See Any of These Artifacts

  24. Above Ground Points Not Removed

  25. LiDAR Not Properly Calibrated Flight lines should be within the vertical accuracy specification

  26. QA/QC of LiDAR Data DO NOT TAKE THIS STEP LIGHTLY, PLAN EARLY ON HOW YOU WANT TO DO THIS!!!

  27. Questions Kenny Legleiter Project Manager Merrick & Company 303-353-3837 Kenny.legleiter@merrick.com www.merrick.com

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