Seattle

ftp://green.kingcounty.gov/transfer

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.