2006 USGS North Puget Sound LIDAR survey
Ralph Haugerud
U.S. Geological Survey
c/o University of Washington
Seattle, WA
31 March 2008
rhaugerud@usgs.gov
Overview of survey
In 2006 the U.S. Geological Survey contracted for a
lidar survey of most of western Whatcom and Skagit counties,
Washington, including
the area bordering the Skagit River as far east as Ross Dam. The
resulting data are presented here. Note
that these are not Puget Sound Lidar Consortium data. The data were
acquired to different specifications by a different contractor.
The survey was designed in accordance with FEMA lidar data
collection standards to
provide on-ground pulse spacings of no greater than 1.4 meters, or
approximately 0.5 pulse/m2. The task order for this survey
specified
horizontal accuracy of 1 m or better (RMSE), vertical accuracy of 18.5
cm RMSE (37 cm in vegetated areas), and return classification adequate
to remove 95% of all outliers, 95% of all vegetation, and 98% of all
buildings. Data were acquired in May, June, August, and September 2006,
using
Leica ALS-50 and Optech 2050 instruments. Data quality is discussed further here.
These data are in the public domain and there are no legal restrictions
on their use. If
you choose to note the source of the data, please credit the United
States
Geological Survey. The USGS does not warrant that these data are fit
for
any use. You are responsible for verifying that these data
are fit for the uses you put them to. Please see Data quality.
Acknowledgements--Vivian
Queija and H. Lee Case (USGS) coordinated and arranged for funding of
the North Puget
Sound survey, with support from Terry Curtis (Washington Department of
Natural Resources) and Josh
Greenberg (Skagit County). Data were acquired by The Sanborn Map Company under a
specific limited offer to the USGS for reduced-cost lidar data. The
acquisition contract was written
and managed by the National Geospatial Technical Operations Center
(NGTOC) of the USGS. Ralph Haugerud (USGS) rewrote ASCII XYZ files and
built DEMs and images from the point lists delivered by Sanborn.
Data layers and downloads
Two data layers were delivered: all-return point lists in LAS
1.1-format files, with each file covering an area 3,000 ft x 3,000 ft,
and ASCII-format XYZIR files (X,Y,Z, intensity, and return number) of
ground points,
tiled according to the same scheme.
The LAS files are presented here as delivered. All have been checked
for readability. ASCII XYZ data and
bare-earth DEMs presented here were constructed from the delivered
XYZIR files. Highest-hit DEMs were constructed from the data in the LAS
files.
All data are in Washington State Plane projection, North zone,
horizontal datum NAD83, units U.S. Survey Feet. The vertical datum is
NAVD88, Geoid03, units feet.
As delivered by the contractor. LAS 1.1
format, point record format 1. See
Documentation
for a
spatial index to these tiles. Note that no files were delivered for
tiles PS5494, PS5495, PS5496, and PS5497. 6,135 files.
ASCII XYZ files of ground points lists of
files
Comma-delimited, X (easting) Y
(northing) Z (elevation) data, one point per line. Zip-compressed. For
the most part, derived from the XYZ-intensity-return#
files delivered by the contractor. Retiled to 3,000-ft square tiles
with boundaries at even values of State Plane easting and northing and
named by easting and northing, e.g., file x1584y642.xyz.zip has its
southwestern corner at 1,584,000 feet easting and 642,000 feet
northing. See
Documentation for a spatial
index to these tiles. 6,514 files.
6-ft XY resolution floating-point Z
rasters constructed from retiled XYZ ground points. A triangulated
irregular network (TIN) was constructed from ground points, then
sampled to a raster via the ArcInfo TINLATTICE command with LINEAR
interpolation. The resulting raster was clipped at the data-area
boundary to avoid interpolation artifacts at re-entrants in the survey
boundary. See
Data quality for
discussion
of known artifacts.
Gzip-compressed ArcInfo export (.e00) files. Each file corresponds to
approximately 1/4 of a standard USGS 7.5-minute quadrangle.
Data in file is for minimum bounding rectangle for quarter-quadrangle,
thus file areas overlap slightly.
The naming scheme is described in
qq_scheme.pdf.
224 files.
6-ft XY resolution floating-point Z
rasters constructed from 1st returns as identified in the LAS files.
1st returns were isolated and
sorted into 6 ft x 6 ft cells.
Highest-hit
DEM elevation is the the elevation of the highest 1st return in each
cell. Cells with no 1st returns have value NODATA. See
Data quality for discussion of
known artifacts.
Gzip-compressed ArcInfo export (.e00) files. Each file corresponds to
approximately 1/4 of a standard USGS 7.5-minute quadrangle. Data in
file is for minimum bounding rectangle for quarter-quadrangle, thus
file areas
overlap slightly.
The naming scheme is described in
qq_scheme.pdf.
224 files.
6-ft XY resolution JPEG images of the bare-earth and highest-hit
surface models. Images calculated with illumination from NE at 45
degrees above the horizon. NODATA areas are white. There is some
degradation because of image compression. Users who need the utmost
possible detail should calculate their own images from the appropriate
DEM.
Each image corresponds to approximately 1/4 of a standard USGS
7.5-minute quadrangle. Images overlap slightly. The naming scheme is
described in
qq_scheme.pdf. For use
in a GIS, be sure to download the world (.jgw) file associated with
each image. 448 files for bare-earth images, 448 files for highest-hit
images.
Documentation