Airborne laser swath mapping (ALSM) data of the San Andreas fault

This airborne laser swath mapping (ALSM) data of the San Andreas fault
zone in northern California was acquired by TerraPoint, LLC under
contract to the National Aeronautics and Space Administration in
collaboration with the United States Geological Survey. The data
were acquired by means of LIght Detection And Ranging (LIDAR) using
a discrete-return, scanning laser altimeter capable of acquiring up
to 4 returns per laser pulse. The data were acquired with a nominal
density of 1 laser pulses per square meter achieved with 58% overlap
of adjacent data swaths (all areas were mapped at least twice and
the data combined to produce final products). The data set consists
of 3 parts: (1) the LIDAR point cloud providing the location and
elevation of each laser return, along with associated acquisition
and classification parameters, (2) a highest-surface digital
elevation model (DEM) produced at a 6 foot grid spacing, where each
grid cell elevation corresponds to the highest laser return within
the cell (cells lacking returns are undefined, usually associated
with water or low reflectance surfaces such as fresh asphalt), and
(3) a "bald Earth" DEM, with vegetation cover and buildings removed,
produced at a 6 foot grid spacing by sampling a triangular irregular
network (TIN). The TIN was constructed from those returns classified
as being from the ground or water based on spatial filtering of the
point cloud. Comparison to GPS-established ground control in flat,
vegetation-free areas indicates that the DEM vertical accuracy is 17
cm (RMSE for 85 points). Bald Earth elevations under vegetation and
for water bodies are less accurate where laser returns from the
ground or water are sparse. The highest surface and bald Earth DEMs
are distributed as georeferenced geotiff elevation and shaded relief
images. The grid cell values in the elevation images are orthometric
elevations in international feet referenced to North American
Vertical Datum 1988 (NAVD-88) stored as signed floating point values
with undefined grid cells set to -99. The shaded relief images are
byte values from 0 (shaded) to 255 (illuminated) computed using ENVI
4.0 shaded relief modeling with an illumination azimuth of 225
degrees, illumination elevation of 60 degrees, and a 3x3 kernel
size. The images are mosaics based on USGS 7.5 minute quadrangle
boundaries. Each mosaic is an east-west strip covering the northern
or southern half of adjacent quadrangles. File names include the
quadrangle names, a northern (N) or southern (S) half designation, a
bald Earth (BE) or highest-surface (FF) designation, and an
elevation image (elev) or shaded relief image (SR) designation. FF
refers to full-feature indicating vegetation and buildings have not
been removed.These data were developed in order to study the
geomorphic expression of natural hazards in support of the National
Aeronautics and Space Administration (NASA) Solid Earth and Natural
Hazards (SENH) Program, the United States Geological Survey (USGS),
and the Geology component of the Earthscope Plate Boundary
Observatory.

Spatial Data Organization Information -

Direct Spatial Reference: Raster
Raster Object Type: Pixel
Row Count: 1285
Column Count: 4398
Vertical Count: 1

Spatial Reference Information -
Horizontal Coordinate System Definition -
Planar -
Map Projection Name: Lambert Conformal Conic
Standard Parallel: 38.333333
Standard Parallel: 39.833333
Longitude of Central Meridian: -122.000000
Latitude of Projection Origin: 37.666667
False Easting: 6561666.666667
False Northing: 1640416.666667
Planar Coordinate Encoding Method: row and column
Coordinate Representation:
Abscissa Resolution: 6.000000
Ordinate Resolution: 6.000000
Distance and Bearing Representation:
Planar Distance Units: survey feet

Geodetic Model:
Horizontal Datum Name: North American Datum of 1983
Ellipsoid Name: Geodetic Reference System 80
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257222