Spatial Data Catalog

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Layer information

Layer Name	SURFACE_WashingtonStateUSGSDEMHillshade
Subject Category	Imagery
Title	30-meter Mosaicked DEM, Greyscale hillshade, and elevation-shaded (colorized) hillshade for entire state of Washington
Feature Count	1
Feature Type	Polygon
Published Date	As needed
Spatial reference	NAD 1983 HARN StatePlane Washington North FIPS 4601 Feet
Open Data Availability	Yes
Place Keywords	Pacific NW, Washington State
Theme Keywords	Elevation, Colorized Hillshade, Elevation Model, Hillshade, Topography
Supplemental Information	All these datasets exist only at KeyRegion index level.

Attribute information

OBJECTID From ESRI	Description Internal feature number. Domain Sequential unique whole numbers that are automatically generated.
Shape From ESRI	Description Feature geometry. Domain Coordinates defining the features.
Shape_Length From Esri	Description Length of feature in internal units. Domain Positive real numbers that are automatically generated.
Shape_Area From Esri	Description Area of feature in internal units squared. Domain Positive real numbers that are automatically generated.
MosaicID No Source Noted	Description Not Found Domain Not Found

Purpose

DEM and greyscale hillshade are available as 30-meter grid data for subsequent raster processing and analysis for areas outside of extent of higher resolution Lidar and 10-meter USGS data.

Colorized (elevation-shaded) hillshade is resampled at 900 feet, providing a coarser but manageable file for cartographic backdrop.

Abstract

Single 30-meter mosaick for Digital Elevation data for Washington State.

Standard derived grey-scale hillshade and elevation-shaded hillshade using green to brown shading..

Contact information

Maintained by	KCGIS Center
Primary	KCGIS Center giscenter@kingcounty.gov

Constraints

Access	None
Use	These data are general elevation data and should be used at appropriate scale, even for general cartographic applications. They should not be used for detailed elevation analysis.

Change history

5/1/2005	Western washington mosaick was first converted from BIL format to ESRI Grid format. Then reprojected to King County Standard projection of WA State Plane N, Zone 5601, HPGN, Units Feet. The Z-value was not consistent with the original UTM units of feet. Comparison to more detailed Lidar data for King County area indicated that the DEM elevation values were 2.75x greater than the Lidar values. The Grid values were recalculated to the Lidar base by dividing the z-value by 2.75. Eastern washington mosaick was imported as a ESRI Grid. Reprojected from UTM Zone 11 to KC projection. Z-value in meters was converted to feet by multiplying z-value by 3.2808. The two state halves were merged using the GRID merge command in order of (eastdem,westdem). The merged DEM was processed using Setnull (washdem == 0, washdem) to convert the 0 values to Null. This was done so that the 0 values would not appear in the hillshade image. The DEM was hillshaded using the default arguments and converted to an image using the gridimage command. The colorized version of the hillshade was created using ArcGIS with 50% transparency for hillshade overlain on DEM. The colorramp was imported from a layer file (/plibrary3/keyregion/elevation/elevationcolorramp.lyr) to assign same values as used in the more detailed colorized hillshade created from the Lidar data.