1. Understanding LIDAR Technology
Brian Mayfield, CP, GISP, GLS
Timothy A. Blak, GS, PLS, CFM

2. Brief Introductions Brian Mayfield, CP, GISP, GLS
Dewberry Program Manager to VGIN
Tim Blak, GS, PLS, CFM
Appendix A of the Map Modernization Guidelines (
NDEP (National Digital Elevation Program) Guidelines for Digital Elevations Data (

3. Our Role in the Industry
Trusted Advisor
North Carolina
Maryland
Mapping Solutions Provider
USGS GPSC
NOAA CSC
FEMA Regional IDIQ Study Contractor
Not a Mapping Firm
No Acquisition Resources (not tied to any specific technologies or brands)
Industry Leading QA/QC Services
NOAA
Statewides

4. What is LIDAR LIght Detection And Ranging Active Sensing System
Uses its own energy source
Measures range distances
Based on time between emission, reflection and receive time
Direct terrain measurements, unlike photogrammetry which is inferred
Day or night operation except when coupled with digital camera
LiDAR provides a point cloud with X.Y,Z positions

5. What LIDAR is NOT All-weather Able to “penetrate vegetation”
Target must be visible within the selected EM spectrum
No rain or fog
Must be below clouds
Able to “penetrate vegetation”
LIDAR can penetrate openings in the vegetation cover but cannot see through closed canopies

6. Animation

7. LIDAR Components Three major components of a LIDAR system GPS
Inertial Measurement Unit
Laser Range Finder

8. Laser Returns First Last Intermediate Ideal for surface models
Ideal for generating bare-earth terrain models
Intermediate
Ideal for determining vegetation structure

9. Laser Returns
Courtesy of EarthData Technologies

10. LIDAR data points - X, Y, Z
Top View
Side View
Courtesy
of Terrapoint

11. Intensity Images Measures the amount of light returning to the sensor
Developing technology – infancy stage
Can now be used for stereo-compilation to generate 3D breaklines (“LIDARgrammetry)

12. Intensity Imagery

13. Full Point Cloud Surface Model

14. Surface Model

15. Cityscape Surface Model

16. Cityscape Ground Model

17. Full Point Cloud Surface Model

18. LIDAR Uses
Courtesy
of Terrapoint

19. LIDAR Uses

20. Accuracy Standards
FEMA – Guidelines and Specification for Flood Hazard Mapping Partners Appendix A: Guidance for Aerial Mapping and Surveying
NDEP Guidelines For Digital Elevation Data

21. FEMA’s Criteria for Topographic Data
For either photogrammetry or LIDAR:
Accuracy equivalent to 2’ contours or better for flat terrain (Accuracyz = 1.2’ at 95% confidence level)
Vertical accuracy at 95% confidence level = Accuracyz = x RMSEz
Accuracy equivalent to 4’ contours or better for rolling to hilly terrain (Accuracyz = 2.4’ at 95% conf level)

22. Accuracy Equivalencies
NMAS
Contour
Interval
90%
Conf
NSSDA
95%
RMSEz 2’ 1’
1.2’
0.6’
18.5 cm 4’
2.4’
37.0 cm

23. Quantitative Verification NDEP Standards as of Jan. 2003
Fundamental Vertical Accuracy. For open terrain only, compute RMSEz. Report Accuracyz as: “Tested __ (meters, feet) Fundamental Vertical Accuracy at 95% confidence level in open terrain based on RMSEz x ”
Supplemental Vertical Accuracy. For all other land cover categories, determine 95th percentile error(s). Report Accuracyz as: “Tested __ (meters, feet) Supplemental Vertical Accuracy at 95th percentile in weeds, crops, scrub, forests, urban areas, etc.” and document outliers. AND/OR
Consolidated Vertical Accuracy. Report Accuracyz as: “Tested __ (meters, feet) Consolidated Vertical Accuracy at 95th percentile in open terrain, weeds, crops, scrub, forests, urban areas, etc.” and document outliers.

24. Contours
Once the elevation model is created - contours are just a click away…or are they?
The key to creating good contours is to control their behavior
Controlling their behavior can be expensive using traditional methods
New methodologies are being developed for LIDAR such as hydro-enforced contours or by “LIDARgrammetry”

25. Contours
Two Types of Contours
Engineering
Topographic

26. LIDAR Contours

27. Breaklines Linear features that control surface behavior
Can be 2D or 3D
Traditionally derived from stereo photogrammetry or from surveys
Can use LIDAR and Intensity to create breaklines or can use Hydro-enforced method

28. Pricing

29. Questions?