Assateague Island Sand Areas Extracted from Orthoimagery, 1989 - 2013

Assessing the physical change to shorelines and wetlands is critical in determining the resiliency of wetland systems that protect adjacent habitat and communities. The wetland and back-barrier shorelines of Assateague Island, located in Maryland and Virginia, changed as a result of wave action and storm surge that occurred during Hurricane Sandy, which made landfall on October 29, 2012. The impact of Hurricane Sandy will be assessed and placed in its historical context to understand the future vulnerability of wetland systems. Making these assessments will rely on data extracted from current and historical resources such as maps, aerial photographs, satellite imagery, and lidar elevation data, which document physical changes over time. This USGS Data Series publication includes several open-ocean shorelines, back-island shorelines, back-island shoreline points, sand area polygons, and sand lines for Assateague Island that were extracted from orthoimagery (ortho aerial photography) dated from April 12, 1989 to September 5, 2013. This dataset consists of polygons that represent the sand areas found in orthoimagery taken on the date specified in the filename and in the Date_ field in the feature attribute table. Orthoimagery of Assateague Island were acquired in digital format from U.S. Department of Agriculture (USDA), U.S. Geological Survey (USGS) and Virginia Geographic Information Network (VGIN) courtesy of the Commonwealth of Virginia. Prior to processing, the images were trimmed to the Assateague Island area. Using ERDAS Imagine 9.3, the images were classified into 10-40 classes that were coded either sand or not sand. Using ArcGIS 10.1, the resulting coded raster datasets were converted to polygons and edited. The following list provides additional details about the orthoimagery used. The sand areas for each date is in a separate dataset (shapefile) named asis_sand_po_*.shp where the date, in YYYYMMDD format, replaces the asterisk. The orthoimage date for each polygon is also included in the shapefile attribute table Date_ field.
Date State Type Source Resolution
198904129(1) MD DOQQ USGS 1 meter (m) 19940320 VA DOQQ USGS 1 m 20041105 VA NAIP USDA 2 m 20050608 VA NAIP USDA 2 m 20050615 MD NAIP USDA 1 m 20060528 VA NAIP USDA 2 m 20060701 MD NAIP USDA 2 m 20070622 MD NAIP USDA 1 m 20080525 VA NAIP USDA 1 m 20090626 MD NAIP USDA 1 m 20090726 VA NAIP USDA 1 m 20090807 VA NAIP USDA 1 m 20110530 VA NAIP USDA 1 m 20110602 MD NAIP USDA 1 m 20120512 VA NAIP USDA 1 m 20130315 VA VBMP VGIN(2) 1 m(3) 20130905 MD NAIP USDA 1 m
DOQQ Digital Orthophoto Quarter Quads NAIP National Agriculture Imagery Program VBMP Virginia Base Mapping Program
(1)Color Infrared orthoimagery; all others are natural color. (2)Imagery courtesy of the Commonwealth of Virginia. (3)Resampled from 1-foot resolution imagery.