Transcript Presentation: Understanding USGS LiDAR Base Specification Version 1.0 (Quantum Spatial)

High Accuracy Helicopter Lidar
& Mapping
Jeffrey B. Stroub, CP,RLS,PPS,SP
Vice President Business Development
September 9, 2014
Understanding
USGS LiDAR
Base Specification Version 1.0
Jeff Stroub CP, RLS, PPS, SP
Vice-President Business Development
September 16, 2014
USGS LiDAR Base Specification Version 1.0
Goal USGS Base Specification
• Consistency – all USGS funded LiDAR Collections
• USGS Interest is only LiDAR Derived Elevation Models
• USGS Scope specific to their mission
– Hydro-Flattened surface
– Hydro Enforced optional surface
• A carefully planned project may support other uses
– USGS Version 1.1 in concept stage
H. Karl Heidemann, GISP
Physical Scientist
U.S. Geological Survey/EROS
U.S. Department of the Interior
U.S. Geological Survey
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 …
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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 revision
5/25
6/25
ASPRS 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 quantities
7/25
Lidar Specification Changes
 QL2 is the minimum QL for 3DEP lidar collections.
 2 points/m2
 10 cm RMSEZ
 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.
8/25
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 square
LiDAR Accuracy
Accuracy is dependent on:
• Flying height
• Sensor parameters
– Rep Rate
– Scan Angle
– Scan frequency
• System accuracy
• Terrain
• Vegetation
• Baseline distance
– Location of base station to Aircraft
LiDAR Project Planning
• Plan based on
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Workable blocks of data
Delivery tiles
Baseline requirements
Flightline distance
limitations
Control locations
Accuracy
Application
Topography
Processing Steps
1.
2.
3.
4.
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9.
GPS Processing
QC GPS
IMU Processing
QC IMU
Calibration
Check Calibration
LAS point Cloud Output
Verify coverage
Classification
1. Sub sample for Macros
2. Breakline generation
10. QC Manual Editing
11. QC process
12. Generation products
13. Check Deliverables
Full Return Surface Model
LiDAR Classified .LAS File
Classification
Manual Editing
USGS Product
Hydrologically – Flattened (Hydro-Flattened) –
USGS Standard Product
Processing 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.
Breaklines
• Breakline specifications vary by project and point
densities
• Hydrologically-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 product
Bare-Earth Surface without Breaklines
Bare-Earth Surface with Breaklines
Breaklines
• If 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
development
• Breakline generation depends on source material –
formerly Photogrammetry now LiDAR derived
Breaklines
• USGS Spec.
• 100 Feet River
• 2 Acre
Breaklines
Breaklines
Breaklines
Breaklines
A 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.
Breaklines
After placing the red XBAR lines and setting their elevation so
they monotonic you are ready to drape water breaklines
Breaklines
This is a 5000’ x 5000’ Tile
This is a full tile with the
water bodies and river
collected. The red XBARs
have been placed and the
elevations have been set.
Breaklines
The Final check to make sure
the river breaklines are monotonic
is 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.
Bare-Earth Surface
Bare-Earth with Breaklines – Hydro
Flattened Surface
Bare-Earth Surface - Hydro Flattened
Bare-Earth with Contours processed
through a Hydro Flattened Surface
Hydro Flattened - Bare-Earth Surface
Hydro Flattened Surface with Flood
Stage Introduced
Bare-Earth with Breaklines – Hydro
Enforced Surface
Bare-Earth Surface Hydro Enforced
Bare-Earth with Contours processed
through a Hydro Enforced Surface
Hydro Enforced Bare-Earth Surface
Hydro Enforced Surface with Flood
Stage Introduced
Accuracy
Accuracy
Standard USGS Deliverables
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Hydro-flattening per USGS water surface requirements
No single line drain breaklines – optional
Metadata – extraneous
Raw point cloud in .LAS – file size fixed at 2gb
Classified Point cloud – USGS standard Bare-Earth
Surface (Raster DEM) per classification scheme
• Breaklines per USGS specification - ESRI feature class
• No contour processing
Project Reporting
• Designed to USGS and other agency requirements
Questions and Answers
Thank You