Title: Seeing through the trees: LIDAR for the Puget Lowland
1Seeing through the trees LIDAR for the Puget
Lowland
- Ralph Haugerud, Craig Weaver
- U. S. Geological Survey
- Jerry Harless
- Puget Sound Regional Council
- and thanks to TerraPoint LLC, Houston TX
2- Why LIDAR?
- What is LIDAR?
- How are we doing LIDAR?
- What are we finding?
3In some places, it is easy to see where the
active faults are.
30 km
4In other places, it is not.
Seattle
Tacoma
30 km
5What are the salient differences?
SF Bay area Puget Lowland
slip rate 3 cm/yr strike slip 4 mm/yr shortening
average tree height ? 10 ft ? 100 ft
age of landscape 106 years 18,000 years
6age ? slip rate feature size
- 18,000 yr ? 1 mm/yr 18 m
- 106 yr ? 1 mm/yr 1 km
- In the Puget Lowland, to see a fault with the
same slip rate as in the SF Bay area, we have to
look more closely.
7LIght Detection And Ranging
- Airborne scanning laser rangefinder
- Differential GPS
- Inertial Navigation System
- 30,000 points per second at 15 cm accuracy
-
- 4001000/mi2, 106 points/mi2, or
0.040.1 cents/point - Extensive filtering to remove tree canopy
(virtual defor-estation)
8(No Transcript)
910-meter DEM from contours
1012-ft DEM from LIDAR
11Picture Oblique view of S end Rockaway Beach
12High-resolution LIDAR topography
13Uses for high-resolution topography
- Finding faults (earthquake frequency, kinematics)
- Geologic mapping
- Landslide hazards
- Flood hazards, groundwater infiltration, runoff
modelling - Fish habitat
- Precision forestry
- Noise propagation
14Why is LIDAR better than photogrammetry?(Its
the trees)
Suppose timber allows 1 of 3 arbitrary rays to
reach ground 1/3 of ground can be surveyed by
LIDAR
Photogrammetry requires 2 separate views of a
point only 1/9 of ground will be locatable
15Bainbridge Island,KPUD1996-1997
Seattle
Snoqualmie, USGS-NMD 1998-2001?
Tacoma
16Puget Sound LIDAR Consortium
Participants Expertise
Kitsap County Kitsap PUD City of Seattle Puget Sound Regional Council NASA USGS (exclusive of USGS) Contracting Surveyor prior LIDAR experience Geologist GIS
17Puget Sound LIDAR Consortium
- No formal structure
- One agenda
- One contract
- Separate payments
- Share data
- Release all data to public domain
(www.GetItYourselfBob, to be hosted by UW
library)
18PSLC
Feb 2001
March-April 2000, Feb 2001
Tacoma
193M
LIDAR already flown
Seattle
to be flown Winter 2001-2002
Tacoma
3.3M
2015 km west of Seattle
Toe Jam Hill fault scarp
Waterman Point scarp
beach uplifted during 900 AD earthquake
21southern Bainbridge Island
22- Fly in winter, when leaves are off
- Near-infrared laser doesnt penetrate clouds,
rain - Errors
- Largest are in anglesup to 1 m x-y error
- Ranging error 15 cm z error!
- 2/3 of surveyed points on trees and buildings
remove with automatic geometric filtering - Multiple reflections from one laser pulse
better filtering
23- Optimum working distance circa 1 km
- Adequate reflection brightness
- Keep laser eye-safe
- Spot diameter decimeters to meters
- Spot spacing 1 to 5 meters
- Multiple passes
- multiple look angles
- higher point density
- internal consistency check
- 400 - 1,000 / mi2