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Elevation Contours Dataset for Delaware

Elevation Contours Dataset for Delaware
Primary Data Category:
Elevation
Publication Date:
Nov 2008
Update Status:
Completed
Summary:

Elevation contours at 2 foot intervals for the State of Delaware were produced for New Castle and Kent Counties based on the 2007 LIDAR) and for Sussex County (based on the 2005 LIDAR.) Data are in line shapefile format.

Downloads and Data


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Geography
Accuracy Information

Sussex County
Compiled to meet 2-meter horizontal accuracy @ 95% confidence level. Meets or exceeds FEMA Accuracy standard for use in flood mapping and remapping work.

Compiled to meet 15 centimeter vertical accuracy @ 95% confidence level. Actual observed average accuracy for the original DEM base data is 10.2 centimeters.


Spatial Reference System(s)
NAD83 Delaware State Planre Meters (EPSG:26957, EPSG:2776, or ESRI:102257 should all work fine)

Use Constraints

Please give proper credit to the Delaware Geological Survey.

Additional Notes

Elevation contours at 2 foot intervals for the State of Delaware were produced for New Castle and Kent Counties based on the 2007 LIDAR) and for Sussex County (based on the 2005 LIDAR.) Data are in line shapefile format.

The Sussex County 2-foot contour dataset was created in a joint effort between the Delaware Geological Survey (DGS) and the U.S. Geological survey (USGS). These data are intended to provide both contour-data for use by the state of Delaware, and digital elevation data for use by USGS in the elevation layer of The National Map. The source of the digital elevation model is LiDAR data acquired between January 2002 and March 2005 using the NASA Experimental Advanced Airborne Research Lidar (EAARL) platform. Once acquired the data were processed by USGS personnel into both 2-foot contours and digital elevation models.

LiDAR data was acquired for New Castle and Kent Counties. Data was acquired at a 1.4/1.0 meter point spacing. An extract of this dataset was developed that represented the bare earth data. The bare earth was produced at a 10-20 interval to support contour generation. Once the LiDAR enhancement process was complete, overlapping tiles of DTM data are first extracted from the DTM. Overlapping DTM data enables the contours to be accurately generated to the tile edge, eliminating possible tile edge errors. Land use hydro polygons from Sanborn's updated land use dataset were integrated with the DTM to support hydro enforcement of contours and to flatten water bodies. A TIN was then derived and contours were generated. Isloated contours representing contours less than 75' in length were removed. Contour smoothing procedures were applied to achieve an aesthetic appearance in accordance with standards established by the State. Manual editing was completed on the datasets to complete the process. Contours were reviewed in comparison to the 2007 orthoimagery One developed contours were edgematched to existing Sussex County contour data. No spot elevations or contour labels were produced as part of this project.