Jeffrey B Stroub CPRLSPPSSP Vice President Business Development September 9 2014 Jeff Stroub CP RLS PPS SP VicePresident Business Development September 16 2014 Understanding USGS LiDAR ID: 285145
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High Accuracy Helicopter Lidar & MappingJeffrey B. Stroub, CP,RLS,PPS,SPVice President Business Development September 9, 2014
Jeff Stroub CP, RLS, PPS, SP
Vice-President Business Development
September 16, 2014
Understanding USGS LiDAR
Base Specification Version 1.0Slide2
USGS LiDAR Base Specification Version 1.0Slide3
Goal USGS Base SpecificationConsistency – all USGS funded LiDAR CollectionsUSGS Interest is only LiDAR Derived Elevation ModelsUSGS Scope specific to their mission Hydro-Flattened surface Hydro Enforced optional surfaceA carefully planned project may support other usesUSGS Version 1.1 in concept stageSlide4
H. Karl Heidemann, GISP
Physical Scientist
U.S. Geological Survey/EROSSlide5
5/25
Background
In response to ARRA funding for USGS LiDAR collection, development of a common minimum specification was begun in early 2009; the
USGS NGP Lidar Base Specification, Version 1.0
was published in the summer 2012: .
Time marches on …
NEEA Study on national LiDAR value published
The 3DEP established
ASPRS Accuracy Standards developed
Technical advances in the industry
The now 5 year-old v1.0 Specification requires revisionSlide6
6/25Slide7
7/25ASPRS Accuracy Standard Alignment
Alignment to ASPRS Accuracy Assessment Methodology
NVA on point cloud assessed in single-return areas
VVA must be met (excluding delineated Low Confidence areas)
CVA is no longer reported
Use of ASPRS recommended check point quantitiesSlide8
8/25Lidar Specification Changes
QL2 is the minimum QL for 3DEP lidar collections.
2 points/m
2
10 cm RMSE
Z
LAS Version 1.4 is required.
OGC Well Known Text Georeference information required
LAS Point Record Format 6, 7, 8, 9, or 10 are required.
Proper use of Withheld and Overlap flags required.
Metadata for LiDAR files.
LiDAR metadata tags suggested in v1.0 are required in v1.1.Slide9
LiDAR Specification Changes
2GB limit on swath file size has been removed.
Flightline Overlap requirement has been removed.
Scan Angle guideline has been removed.
Classification:
Two added required classifications
Bridges (17)
High Noise (18)
Classification Accuracy for : QL2, QL1, and QL0
Test areas are now 1 square km, not 1 km squareSlide10
LiDAR Accuracy Accuracy is dependent on:Flying heightSensor parametersRep RateScan Angle Scan frequency
System accuracy Terrain
VegetationBaseline distanceLocation of base station to AircraftSlide11
Plan based onWorkable blocks of dataDelivery tilesBaseline requirementsFlightline distance limitationsControl locationsAccuracyApplicationTopography
LiDAR Project PlanningSlide12
Processing StepsGPS Processing
QC GPSIMU Processing
QC IMUCalibration
Check CalibrationLAS point Cloud OutputVerify coverageClassificationSub sample for MacrosBreakline generationQC Manual Editing
QC process
Generation products
Check DeliverablesSlide13
Full Return Surface ModelSlide14
LiDAR Classified .LAS FileSlide15
ClassificationSlide16
Manual EditingSlide17
USGS ProductHydrologically – Flattened (Hydro-Flattened) – USGS Standard ProductProcessing of LiDAR derived surface (DEM or TIN) so mapped water surfaces are flat from bank to bank, and rivers demonstrate a gradient change. Breaklines are used to establish elevations for water surfaces consistent with surrounding topography, and produce aesthetically acceptable water surfaces in final DEM or TIN. Hydro flattening is driven solely by USGS cartographic mapping needs.Slide18
BreaklinesBreakline specifications vary by project and point densitiesHydrologically-Conditioned (Hydro-Conditioned)Processing of a DEM or TIN so that the flow of water is continuous across the entire terrain surface whether flow in channel or not (evaluation basin / large areas)Hydrologically –Enforced (Hydro-Enforced)Process of mapping water bodies so that lakes and reservoirs are at level surface and so that streams flow downhill……(typically used for hydrologic and hydraulic modeling) – optional productSlide19
Bare-Earth Surface without BreaklinesSlide20
Bare-Earth Surface with BreaklinesSlide21
BreaklinesIf a DEM is required for a project and the breaklines fail acceptance, the DEM will fail acceptance.LiDAR industry has come along way in breakline developmentBreakline generation depends on source material – formerly Photogrammetry now LiDAR derivedSlide22
BreaklinesUSGS Spec.100 Feet River2 AcreSlide23
BreaklinesSlide24
BreaklinesSlide25
BreaklinesSlide26
BreaklinesSlide27
BreaklinesSlide28
BreaklinesA Cross Section is viewed to see if the red XBAR line is set at the lowest elevation.The red XBAR line elevation can be changed if not correct.Slide29
BreaklinesAfter placing the red XBAR lines and setting their elevation so they monotonic you are ready to drape water breaklinesSlide30
BreaklinesThis is a 5000’ x 5000’ TileThis is a full tile with the water bodies and river collected. The red XBARs have been placed and the elevations have been set.Slide31
BreaklinesThe Final check to make sure the river breaklines are monotonicis to run contours. A surface is created with the river breaklines only. Contours are developed for That surface and contours are created crossing only the river breaklines.Slide32
Bare-Earth SurfaceSlide33
Bare-Earth with Breaklines – Hydro Flattened SurfaceSlide34
Bare-Earth Surface - Hydro FlattenedSlide35
Bare-Earth with Contours processed through a Hydro Flattened SurfaceSlide36
Hydro Flattened - Bare-Earth SurfaceSlide37
Hydro Flattened Surface with Flood Stage IntroducedSlide38
Bare-Earth with Breaklines – Hydro Enforced SurfaceSlide39
Bare-Earth Surface Hydro EnforcedSlide40
Bare-Earth with Contours processed through a Hydro Enforced SurfaceSlide41
Hydro Enforced Bare-Earth SurfaceSlide42
Hydro Enforced Surface with Flood Stage IntroducedSlide43
AccuracyField surveying required to establish:FVA – Fundamental Vertical accuracySVA – Supplemental Vertical AccuracyCVA – Consolidated Vertical Accuracy
RMSE Fundamental Vertical Accuracy (FVA
) using check points in open terrain.
FVA = 1.9600 * RMSE(z) = Sqrt[(Σ(Zdata(i) . Zcheck
(
i
))
2 )/n]Slide44
AccuracySlide45
AccuracySlide46
Standard USGS DeliverablesHydro-flattening per USGS water surface requirementsNo single line drain breaklines – optionalMetadata – extraneousRaw point cloud in .LAS – file size fixed at 2gbClassified Point cloud – USGS standard Bare-Earth Surface (Raster DEM) per classification schemeBreaklines per USGS specification - ESRI feature class
No contour processingSlide47
Project ReportingDesigned to USGS and other agency requirements Slide48
Questions and AnswersThank You