Understanding LIDAR Technology Brian Mayfield, CP, GISP, GLS Timothy A. Blak, GS, PLS, CFM.
-
Upload
melvin-maxwell -
Category
Documents
-
view
220 -
download
0
Transcript of Understanding LIDAR Technology Brian Mayfield, CP, GISP, GLS Timothy A. Blak, GS, PLS, CFM.
Understanding LIDAR Understanding LIDAR Technology Technology
Brian Mayfield, CP, GISP, GLS
Timothy A. Blak, GS, PLS, CFM
Brief IntroductionsBrief Introductions Brian Mayfield, CP, GISP, GLS
Dewberry Program Manager to VGIN
Tim Blak, GS, PLS, CFMAppendix A of the Map Modernization Guidelines (
http://www.fema.gov/pdf/fhm/frm_gsaa.pdf)NDEP (National Digital Elevation Program)
Guidelines for Digital Elevations Data (http://www.ndep.gov/NDEP_Elevation_Guidelines_Ver1_10May2004.pdf)
Our Role in the IndustryOur Role in the Industry Trusted Advisor
North CarolinaMaryland
Mapping Solutions ProviderUSGS GPSCNOAA CSCFEMA Regional IDIQ Study Contractor
Not a Mapping FirmNo Acquisition Resources (not tied to any specific
technologies or brands) Industry Leading QA/QC Services
NOAAStatewides
What is LIDARWhat 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
What LIDAR is NOTWhat LIDAR is NOT All-weather
Target must be visible within the selected EM spectrum
No rain or fogMust be below clouds
Able to “penetrate vegetation”LIDAR can penetrate openings in the vegetation
cover but cannot see through closed canopies
AnimationAnimation
LIDAR ComponentsLIDAR Components Three major
components of a LIDAR system
1. GPS
2. Inertial Measurement Unit
3. Laser Range Finder
Laser ReturnsLaser Returns First
Ideal for surface models
LastIdeal for generating bare-earth terrain models
IntermediateIdeal for determining vegetation structure
Laser ReturnsLaser Returns
Return Pulses
Incoming Pulse0
20
Time(nanosec)
0
40
60
80
100
120
140
20
Return#1
Return#2
Return#3
Return#4
Return Pulses
Incoming Pulse
Return Pulses
Incoming Pulse0
20
Time(nanosec)
0
40
60
80
100
120
140
20
Return#1
Return#2
Return#3
Return#4
0
40
60
80
100
120
140
20
Return#1
Return#2
Return#3
Return#4
Courtesy of EarthData Technologies
LIDAR data points - X, Y, ZLIDAR data points - X, Y, Z
Top View
Side View Courtesy of Terrapoint
Intensity ImagesIntensity 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)
Intensity ImageryIntensity Imagery
Full Point Cloud Surface ModelFull Point Cloud Surface Model
Surface ModelSurface Model
Cityscape Surface ModelCityscape Surface Model
Cityscape Ground ModelCityscape Ground Model
Full Point Cloud Surface ModelFull Point Cloud Surface Model
LIDAR UsesLIDAR Uses
Courtesy of Terrapoint
LIDAR UsesLIDAR Uses
Accuracy StandardsAccuracy Standards FEMA – Guidelines and Specification for
Flood Hazard Mapping Partners Appendix A: Guidance for Aerial Mapping and Surveying
NDEP Guidelines For Digital Elevation Data
FEMA’s Criteria for Topographic FEMA’s Criteria for Topographic DataData
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 = 1.9600 x RMSEz
Accuracy equivalent to 4’ contours or better for rolling to hilly terrain (Accuracyz = 2.4’ at 95% conf level)
Accuracy EquivalenciesAccuracy Equivalencies
NMASContourInterval
NMAS90%Conf
NSSDA95%Conf
NSSDARMSEz
2’ 1’ 1.2’ 0.6’18.5 cm
4’ 2’ 2.4’ 1.2’37.0 cm
Quantitative Verification Quantitative Verification NDEP Standards as of Jan. 2003NDEP 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 1.9600.”
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.
ContoursContours 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”
ContoursContours
Two Types of Contours1. Engineering
2. Topographic
LIDAR ContoursLIDAR Contours
BreaklinesBreaklines 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
PricingPricingApproximate Costs Per Square Miles Sq Miles - Tw o Foot Equivalency
0
200
400
600
800
1000
1200
20 50 100 200 500 1000
Sq Miles
Questions?Questions?