County, King, 20071005, Five (5) foot-interval index contour isolines for townships and the entire county. Index contours selected from 5 foot contours(10 foot, 20 foot, 40 foot, 50 foot & 100 foot) for entire county.: King County, King County, WA.
This is a Vector data set. It contains the following vector data types (SDTS terminology):
The map projection used is NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.00025
Ordinates (y-coordinates) are specified to the nearest 0.00025
Planar coordinates are specified in foot_us
The horizontal datum used is D North American 1983 HARN.
The ellipsoid used is GRS 1980.
The semi-major axis of the ellipsoid used is 6378137.0.
The flattening of the ellipsoid used is 1/298.257222101.
Sequential unique whole numbers that are automatically generated.
Integer value defining township and range of tile; i.e., T22R04 would be 2204
Coordinates defining the features.
The contour interval represents a best compromise between the vertical and horizontal accuracy of the source data and the need for a general use cartographic and analysis product. At the contour interval indicated for a given tile the data provide a reasonable depiction of the general shape of the land useful for determining general landform, slope, and elevation. As, by nature, LiDAR data contain some percent of non-ground points, the contours cannot be considered absolute or without error. The index contour attributes allow the data to be reselected or symbolized to display less detail for smaller scale areas.
King County ESA/SAO contract with 3di Technologies, Boulder, CO, 20030101, King County ESA/SAO Lowland LiDAR Project (Phase I) and King County ESA/SAO Upland LiDAR Project (Phase 2): 3di Technologies, Boulder, CO.
Elevation attributes are derived from the LATTICECONTOUR function within ArcInfo and are accurate relative to the vertical accuracy of the underlying bare-earth dgm data.
The contours were generated from ArcInfo lattice grids based on 6-foot center to center posting. Horizontal accuracy will be approximately 1/2 of the posting distance or about 3 feet in areas where point density is high (equivalent to 5-7 feet point spacing). Where point density is considerably reduced due to poorer to-ground penetration rates, the horizontal accuracy will be reduced proportionally and may be only accurate to 10-15 feet and locally accuracy will be even poorer. Areas of built-up manmade features do not have any 'bare-earth' points and any elevation interpretation, including contour delineation, is created by interpolation from the nearest bare-earth points outside the built-up area. In these cases the contour interpretation may accurately reflect the amount of overall slope change but cannot accurately depict the area covered by the built-up feature.
Vertical Datum is NAVD88. The elevation attribute, provided in integer feet, represents an interpretation of the tinned elevation values interpolated to a six-foot centered lattice. Limited testing has indicated that the contours represent LiDAR elevation values within 1/5 of the contour interval though in areas of steep terrain and dense vegetation canopy the contour elevation value should be considered accurate to only 1/2 the contour interval. Locally the contour interpretation of the ground elevation will be poorer, especially in areas of dense vegetation (particularly dense understory vegetation) and areas of steep slope. The contour interpretation is directly related to the vertical accuracy of the underlying bare-earth digital ground model from which it is created. Vertical accuracy of the bare-earth data varies considerably. Quality Assessment evaluation of vertical accuracy indicate that, as a whole, the data exhibits a RMSE (Root Mean Square Error) of 30 cm or less in areas without vegetation canopy or dense subcanopy. This is equivalent to a National Standard for Spatial Data Accuracy (NSSDA) of 58.8 cm at the 95% confidence interval (1.96 x RMSEz). In areas of dense vegetation canopy, but where some bare-earth penetration is available, the data generally has less than 60 cm RMSE, equivalent to 117.6 cm NSSDA Accuracy. Better accuracies are obtained in many areas, but poorer accuracies are also prevalent due to low penetration rates, incomplete vegetation and elevated feature removal, errant points due to multiple reflection travel paths and other edge-effects. Water and areas immediately adjacent to open water areas are always suspect due to the inability to obtain good returns from these surfaces.
Contours cover the entirety of each tile to the extent that LiDAR data is available for that area. No gaps occur within the contour lines.
Processing routines were adjusted and/or contour interval increased to mininimze, though not necessarily, eliminate all crossing contours, especially in areas of steep relief. All contours are labeled. Contours were created on a tile by tile basis, using a buffer of adjacent data to minimize edge effects and to have contours overlay as closely as possible. However township tiles have not been butt-joined and edge-matched. As stated in the Abstract not all tiles contain five-foot contours. This restriction is dependent on the tile's extent (i.e., amount of relief) and whether the tile has elevation ranges less than 1000 feet. For tile-based data stored in the Spatial Data Warehouse, the following image shows all tiles with with five-foot contours (either above or below 1000 feet) and then the only tiles with five-foot contours above 1000 feet. <http://www5.kingcounty.gov/sdc/raster/elevation/images/FiveFootContourDistribution.jpg> One copy of the tiles has been modified for storage in the SDE Geodatabase. These tiles have been clipped to a midline neatline between townships and edgematched. All 5-foot contours above 1000 feet have been removed for all tiles so that no dangling arcs will occur. These tiles will have five foot contours only if there are elevations less than 1000 feet within the tile's extent.
Are there legal restrictions on access or use of the data?
- A cooperative data sharing arrangement between the Puget Sound LiDAR Consortium and King County is allows certain formats of the LiDAR data to be distributed with out license or restriction. Certain processing and data handling charges for necessary cost recovery may apply. Access to raw mass point files is by special request and request evaluation only.
- King County data are made available with the understanding that they shall be used exclusively by the obtainer or his/her authorized agents. Digital products may not be reproduced or redistributed in any form or by any means without the express written authorization of King County. These contours are based upon LiDAR returns which inherently contain some "non ground-surface" values. In addition, the contours were smoothed, as outlined in the Process Section, to create a more traditional cartographic product. As such, these contours represent only the general shape of the land and do not meet the definition of topography per chapter 18.43 of the Revised Code of Washington. These contours do not depict the topography relative to any particular property. Any use of this information without additional verification by competent professionals is inappropriate.
King County disclaims any warranty of use of any digital product or data beyond that for which it was designed.
|Data format:||ESRI Shapefile|
Contact KCGIS Client Services for the cost of reproduction - <http://www.kingcounty.gov/operations/GIS/GISData/GISDataDistribution.aspx>