ChartTiff Countours

The National Elevation Dataset (NED) is a new raster product assembled by the U.S. Geological Survey. NED is designed to provide National elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, perform edge matching, and fill sliver areas of missing data. Artifact removal greatly improves the quality of the slope, shaded-relief, and synthetic drainage information that can be derived from the elevation data. NEDs have resolutions of one-third arc-second (approximately 10 meters) and one arc-second (approximately 30 meters) for the continuous United States, and one arc-secondor the Hawaii, Puerto Rico and Virgin Islands and a resolution of two arc-seconds for Alaska.

The figure below illustrates the results of this artifact removal filtering. NED processing also includes steps to adjust values where adjacent DEM's do not match well, and to fill sliver areas of missing data between DEM's. These processing steps ensure that NED has no void areas and artificial discontinuities have been minimized.

Figure. A shaded-relief representation of the Rockypoint, Wyoming 7.5-minute DEM is shown above on the left. The same area is shown on the right after NED artifact filtering has been performed. The super-imposed red lines are synthetic drainage networks derived from each elevation dataset.

Contour Data

Horizontal Resolution\
1/3 Arc Second resolution for Continental US
Approximately 10 Meters or 30 Feet
1 Arc Second resolution for HI, PR and VI
Approximately 30 Meters or 100 Feet
2 Arc Second resolution for Alaska
Approximately 60 Meters or 200 Feet
Vertical Resolution
1 DeciMeter or 10 CM or approximately 4 Inches
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