Puget Sound LIDAR Consortium
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1998-99 Snoqualmie LIDAR survey
In 1998 the U.S. Geological Survey contracted for an experimental LIDAR
survey of the Snoqualmie valley. After an instrument malfunction that led
to reflying a large part of the survey in 1999 and the usual delays in
processing, the completed survey was delivered in 2000. With the permission
of the USGS, we are posting the gridded DEMs from this survey here.
DEMs are 5-meter grids in UTM10, horizontal datum NAD83, in rectangular
patches that enclose all or part of the relevant USGS 7.5-minute quadrangle.
Elevations are in floating-point meters and the vertical datum is NAVD88.
These data were considerably sparser than the PSLC surveys (nominal
5 meter spot spacing in X and Y, as opposed to 1.5 meter X-Y spacing for
the PSLC surveys). The Fall City quadrangle and the southern
part of the Snoqualmie quadrangle were double flown, giving a higher data
First-return data are not available. Here you will find bare-earth DEMs
and shaded-relief images of the bare-earth DEMs:
||ZIPped .e00 file of 5-meter DEM
||ZIPped JPEG of shaded-relief image
<quadname>.jgw (world file)
||JPEG of shaded-relief image
We have taken considerable care to ensure that these topographic survey
data and derived images are as accurate as possible. We believe most of
these data are adequate for determination of flood hazards, for geologic
mapping, for hydrologic modelling, for determination of slope angles, for
modelling of radio-wave transmission, and similar uses with a level of
detail appropriate to a horizontal scale of 1:12,000 (1 inch = 1,000 feet)
or smaller and vertical accuracy on the order of a foot. Locally, the data
are of considerably poorer quality.
Users should carefully determine the place-to-place accuracy and fitness
of these data for their particular purposes. For many purposes a site-
and use-specific field survey will be necessary.
Note about formats
for raster elevation data
We have posted DEMs as zipped .e00 files. The .e00 file format is verbose
ASCII, expanding gridded DEMs to approximately 4 times their binary size,
but is easily imported into Arcview and Arc-Info and carries projection
information. It can also be deciphered relatively easily: see, for example,
for format description. If this format doesn't work for you, please
The DEMs and images are in rectangular tiles that include the named
7.5-minute quadrangle. Adjacent tiles overlap along their margins. There
should be no invalid values in these DEMs.
As we approve data from the contractor they are posted here. Areas within
many of the bare-earth DEMs can be improved by further processing of the
all-return point data to better isolate bare-earth points. As we make
these improvements we will upgrade the bare-earth DEMs and derivative images
posted here. Users of these data may want to return to this web site to
check for updates, or register to receive automatic notification of updates
for areas they have downloaded.
If you have difficulty loading the data files into your software, cannot
easily transfer large files via the Internet, or would like advice on the
uses and limitations of these data, please contact
This page maintained by PSLC webmaster
--- Last updated : Mon 02 Jul 2001 03:39:42 PM PDT