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Digital Elevation Data
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Overview:
Lidar-Derived
Elevation Data
Light
distance and ranging (lidar) technology
has been used to acquire high-resolution
elevation and return pulse intensity data
for western
King County and the southwestern portion
of Snohomish County.
This
data set is a combination of the Puget
Sound Lidar
Consortium (PSLC)
data collection effort for Vashon Island
and the Seattle-area (2001–2002), and a comparable
collection for the remainder of the county
and the WRIA 8 portion of
Snohomish County through King County’s ESA/SAO
Project from 2002 - 2003.
See
the
Project Area map
(172Kb JPG) for
project area boundaries phases.
Multiple data products include
the Digital Ground Model (dgm) ascii, tin, lattice and hillshade data sets; Digital
Surface Model (dsm, aka top-of-vegetation) data in the same
formats, plus supplemental Last Return and Intensity data.
The PSLC’s extensive cooperation in this data sharing
arrangement has allowed us to develop a seamless digital elevation database,
along with related derived products, for the entire area of interest
(AOI).
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Summary
of Lidar Data Products
There
are sixteen unique lidar data file sets
available from the Spatial Data Warehouse.
Some of these products are available
only at a single tiling level but the
key elevation data sets are provided
in more than one format to assist in meeting
a range of business and analytical needs.
Please contact King
County GIS Client Services for assistance
in determining the correct data set and
format for your requirements.
This summary table can
assist you in understanding the various data set, formats and tiling levels available. Please see the
data description section for a more detailed description
of each data set.
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Summary
of Lidar Data Storage Requirements
The complete county project area and detailed level of the elevation data requires
significant storage capacity. Storage requirements vary depending on the data set of interest and the format in which it is stored.
This summary table provides a
general overview of the data sets, their overall size and individual file size specifications.
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Details: Lidar Data
Products
There are six primary data products developed from the lidar
acquisition projects, some in more than one data format to help meet a range of
business needs and software applications.
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USGS Digital Elevation Data
To supplement the detailed elevation data to be provided by
lidar, Digital Elevation Models (DEM) from the USGS National Elevation Database
(NED) have been downloaded and added to the Spatial Data Warehouse in order to centralize all
elevation data to a single locale. The USGS data covers the entire Puget Sound
lowlands at two different resolutions and is generally the best elevation data
available outside the lidar project areas. In addition to the elevation grids,
the data is available as hillshade images and as a 500-foot index level contour
set. The lower resolution data is provided as a single AOI piece, while the
higher resolution NED data is provided as county-by-county pieces. State-wide elevation data is
not online though a hillshade image covering the entire state is available.
Extent of USGS NED for Puget Sound Lowland
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kingco_ned028 – King County and adjacent counties 28-foot resolution
elevation data. King County model as ArcInfo Grid in \\gisdw\kclib\keyregion\elevation. Other counties also as grids
in \\gisdw\kclib\keyregion\elevation\adjcounty as 'countyname'_ned028.
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reg_dem086 – Entire Puget Sound Lowlands as single ArcInfo Grid at coarser 86-foot resolution. Also available as
hillshade, reg_demghs086.jp2, and as 500-foot generalized contours, reg_demctr500, in shapefile format.
USGS National Elevation Database Metadata
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reg_srt086 – Shuttle Radar Topography Mission elevation data for Puget Sound Lowlands at 86-foot resolution. Alternative
version of regional elevation data. Hillshade available as reg_srtghs086.jp2
Shuttle Radar Topography Elevation Metadata
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wa_demghs999 – Generalized statewide version of ground hillshade provided by WA Dept of Natural Resources.
Statewide ground hillshade Metadata
reg_psdem030, reg_pshsd030, and reg_psctr050 – Digital elevation model, Greyscale hillshade and 50-foot generalized contours for combined bathymetry and elevation model of Puget Sound lowlands. Provided by University of Washington (Finlayson, D.P, 2005).
30-foot combined digital elevation model Metadata
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Access
to Data
for King County
Government Users
Plibrary3 Mapping
Users with access to the King County Spatial Data Warehouse
(i.e., Plibrary2 and Plibrary3) can access the elevation data in a
range of formats and tile sizes. All lidar-derived and USGS elevation data is
found in Plibrary3 at
\\gisdw\kclib\plibrary3. King County users are encouraged to map their ‘J’
drive letter, if available, to
\\gisdw\kclib\ which will allow them access to all three libraries of the
Spatial Data Warehouse from a single drive letter.
Plibrary3 Index and Naming Conventions
In addition to the elevation data stored in Plibrary3, this
library will serve as the central point for all King County enterprise image and
raster data. All data will be organized into a standardized tiling scheme with a
structured naming convention to make data access easier and more informative. A
more in-depth discussion of Plibrary3 and the tiling/naming conventions can be
found in "Plibrary3
Reorganization"
(341 Kb Word Document). The tiling and naming convention is summarized in
the Excel
spreadsheet
Plibrary3 Naming Convention Codes (33 Kb).
Internal GIS users are reminded that they will find that most of
their data needs are met by accessing data prepared at the township-range tile
level (idxptrmbr), found at
\\gisdw\kclib\plibrary3\idxptrmbr.
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Distribution of Data to
Non-King County Government Agencies and the Public
KCGIS
Center Client Services will handle
distribution of the lidar DEM data
for King County. Data from both the
PSLC and King County areas is considered
public domain data and
can be released without any licensing
restrictions. There may be some cost
for media production and delivery.
Recipients and users of the data are
reminded to review all accompanying
metadata for use restrictions and the
discussion of data accuracy and validity.
Through agreement with the PSLC, King County and the
PSLC will serve as repositories and distributors of both lidar data sets.
As released through King County, the standard distributed set will be an
ArcInfo Grid Export file in Zip file format and an accompanying zipped
TIFF hillshade image. Both the Digital Ground Model (DGM) and Digital
Surface Model (DSM) can be provided. This is comparable to the data suite
released through the PSLC, though a different tile scheme is used. King
County data will be delivered in a township-range tile scheme as described
in the following metadata –
FGDC Style metadata
FAQ Style
metadata
ASCII text files of elevation data, image intensity
data and contour interpretations will be provided upon review of
individual request.
As a rule, King County does not redistribute
third-party data such as the USGS National Elevation Database. Users are
encourage to take advantage of the extensive data collection and data
delivery tools available at
http://seamless.usgs.gov/, the USGS National Map website. |
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Revised September 29, 2006
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