This page is a minor modification of the index file
on the CDROM.
PSNERP FY03 bathymetric lidar data
On this disk are final
data from the September-October 2003 survey of the saltwater nearshore of
the City of Seattle, WRIA9 (south King County, including Vashon and Maury
Islands), the Lofall reach of Hood Canal, and Skagit Bay. Note that coverage
of these areas is incomplete: voids range from minimal (City of Seattle,
Lofall) to extensive (Skagit Bay).
These data were acquired by the Joint Airborne Laser Bathymetry Technical
Center of Expertise (JALBTCX), using the new SHOALS 1000 instrument. Derivative
products (classified data points, grids, images) on this disk were produced
by Ralph Haugerud of the U.S. Geological Survey from the survey data acquired
by JALBTCX.
For further information about these data, please contact
Ralph Haugerud
rhaugerud@usgs.gov
206-553-5542
or
Eddie Culpepper
Eddie.Culpepper.Jr@sam.usace.army.mil
251-690-3487
Haugerud and Culpepper are preparing a final report, to be available
online, that will include the data on this disk as well as a revised Report of Survey,
an analysis of data quality, documentation of the processing used to classify
points, and documentation of the rules used to interpolate from surveyed
points to a continuous surface with no-data areas. In the interim, please
cite these data as follows:
Information in the area-specific directories, the draft Report
of Survey, and the information in the xyzc directory except for the point
classification: JALBTCX, written communication, 2004
Information in the composites and tiles directories, and the point classifications within the xyzc directory: R.A. Haugerud, U.S. Geological Survey, written communication, 2004
New filegeodatabase
New version 10 filegeodatabase
derived from the contents of the tile directory.
Disk contents
City of Seattle data, as received from JALBTCX.
Includes lidar data, aircraft trajectories, digital images, and metadata.
Most data are in Washington State Plane north coordinates, datum NAD83, vertical
datum NAVD88. Digital RGB images, located in the images subdirectory, were
acquired with a down-looking camera during lidar data acquisition. They are
accompanied by world files that position the images in the UTM10 coordinate
system. Note that the images are not orthorectified.
Caveat: Some images will appear unreadably dark if level adjustments
are not made. .jgw files contain a rotation component, so they will be unreadable in ArcMap, though they can be converted to grids. But not ones
with messed-up jgw files.
Lofall data, as received from JALBTCX.
Skagit Bay data, as received from JALBTCX.
WRIA9 data, as received from JALBTCX.
Draft Report of Survey as received from JALBTCX
ASCII files of lidar data points. Reformatted, sorted and classified by Haugerud. Format is
easting northing elev
time date classification
1230000.13 179166.98 -27.56 17:10:04.944036 2003271 G
1230000.50 179487.88 -50.03 17:10:06.047652 2003271 G
1230000.63 179814.94 -62.63 17:10:07.210224 2003271 G
easting (first 10 characters) and northing (characters 12 - 21) are Washington State Plane North zone feet
elev (characters 24 to 29) is in feet, referenced to NAVD88
time (characters 31 to 45) is hours:minutes:seconds
date (characters 48 to 54) is YYYYDDD
classification is a single-character code with values of
G ground or bottom
N not-ground, not-bottom (e.g. trees, structures, piers, boats)
B blunder (points with too-low values, perhaps because of multiple reflection)
Points are sorted into tiles with maximum dimensions of 10,000 ft X 10,000
ft. The file name corresponds to the position of the southwest corner of
the tile. That is, file x123y017.xyzc contains points with X-coordinates
(eastings) greater than or equal to 1,230,000 and less than 1,240,000 and
Y-coordinates (northings) greater than or equal to 170,000 and less than
180,000.
Points were classified with a combination of the 'despike' code described
by Haugerud and Harding (2001; see https://pugetsoundlidar.org)
and hand editing. The goal of classification was to identify survey points
on not-ground objects such as boats and floating docks (N) so that they could
be ignored when constructing a bottom model for environmental analysis, and
to flag survey points that are too deep and clearly unreal (B). With a few
exceptions, an effort was made to NOT flag points that appear to be not-ground
because of survey errors, such as some higher-than-average points in areas
of swath overlap. For most tiles, classification of upland points was perfunctory
and is clearly unsatisfactory; much better coverage of the upland areas is
available from the Puget Sound Lidar Consortium.
Zipped e00 (ESRI export format) files of Arc-Info grids. Two grids
are presented for each XY tile. "be" grids are built only from points classified
as "G". "ff" grids are built from all points. For many of the tiles, the be and ff grids are identical, or nearly so.
Grids are in Washington State
Plane North coordinate system, with 6-foot cells. Z values are 4-byte floating point numbers,
datum NAVD88. Six foot cells strongly oversample the lidar data (nominal
point spacing of 4 meters) but are used for compatibility with high-resolution
topography from the Puget Sound Lidar Consortium. Grids were built by constructing
a TIN and then sampling the TIN at regular intervals using the Arc TINLATTICE
command.
Large-area composite "be" grids:
sea_n Seattle north of Elliot Bay. Merged
with upland lidar topography from the Puget Sound Lidar Consortium
sea_s Seattle south of Elliot Bay. Merged
with upland lidar topography from the Puget Sound Lidar Consortium
wria9_n northern part of WRIA9
wria9_s southern part of WRIA9
lofall Lofall reach of Hood Canal, extending
along the SE shore from Salisbury Point to a point about 5 miles SW
skagit Skagit Bay
For each composite there is a corresponding TIFF image with world file. Note
that on the images the blue-to-green color transition is at Z=0 NAVD88, not
at MLLW.
Grids and images are in Washington State Plane North coordinate system.
This directory also includes grid n88-mllw. This low-resolution grid provides
the offsets necessary to convert the grids on this disk, except for those of the Skagit Bay area, to MLLW
vertical datum. To, for example, convert the SEA_N grid to MLLW datum, use
the following ArcInfo GRID commands:
Grid: setwindow SEA_N
Grid: setcell SEA_N /* necessary to force output to 6-ft cells
/* not the 300-ft cells of grid n88-mllw
Grid: SEA_NMLLW = SEA_N - N88-MLLW
n88-mllw was derived from datum translations given by NOAA's VDatum tool (https://chartmaker.ncd.noaa.gov/bathytopo/vdatum.htm).
At present VDatum for Puget Sound does not provide translations as far north
as Skagit Bay, thus n88-mllw does not extend to Skagit Bay.
14 July 2004