Significant Topographic Changes in the United States

Methods

Given that the primary input datasets, NED, SRTM, and NLCD, each have a spatial resolution of 30 meters and the fact that the study area covers the conterminous United States, a considerable amount of data processing was required to detect and quantify areas of significant topographic change.

The NED and SRTM data are each supplied as 1x1-degree tiles defined by lines of latitude and longitude, and these tiles provided a convenient and useful scheme for organizing and processing the input data. A total of 934 1x1-degree tiles cover the conterminous United States (see figure below). Even though the NED, SRTM, and NLCD were partitioned into 1x1-degree tiles for processing efficiency, each dataset is truly seamless-there are no artificial discontinuities across the tile boundaries. Data processing was accomplished with standard geographic information system (GIS) and statistical software tools and was automated as much as possible with scripted command files to standardize the procedures.

Coming Soon

Accuracy Assessment of Elevation Data
Significant Change Thresholds
Filtering of Elevation Difference Mask to Identify True Topographic Changes
Tabulation of Stats ....

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Date published: December 13, 2018
Status: Active

SRTM NED Vertical Differencing

Image differencing has long been used as an effective change detection technique for coregistered digital remote sensing datasets.  One image is simply subtracted from another image on a pixel-by-pixel basis.  As applied to gridded DEMs, the result of image differencing is a differential surface, which is a measure of the spatial distribution of mass displacement.  In a differential surface,...

Contacts: Dean Gesch