1970's Mosaic of Aerial Photography of the Salt River Bay National Historical Park and Ecological Preserve

Aerial photographs taken by NOAA's National Geodetic Survey during 1977 and 1971 were mosaicked and orthorectified by the Biogeography Branch resulting in a single composite mosaic of both years of photography. The resulting image was used to digitize benthic, land cover and mangrove habitat maps of the Salt River Bay National Historic Park and Ecological Preserve (National Park Service), on St. Croix, in the U.S. Virgin Islands. The composite, rather than a single year mosaic, was used because the northward extent and water clarity of photos from any single year were inadequate for the project objectives. The mosaic is centered on the National Park Service Site, located on the north central coast of St. Croix, and extends beyond the park boundaries approximately 3 km to the south, 6 km to the west, 4.5 km to the east, and 0.5 km to the north.

The image was used to create benthic and mangrove habitat maps of the Salt River Bay National Historic Park and Ecological Preserve. The maps support current and future monitoring and management efforts at the site, and support programmatic objectives of the NPS service-wide Inventory and Monitoring Program. In addition to the habitat maps, the georeferenced image may by utilized by the park to examine other resource management issues, including development, deforestation, erosion, etc.

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The National Oceanic and Atmospheric Administration (NOAA) National Centers for Coastal Ocean Science (NCCOS) produced this data for Salt River Bay National Historic Park and Ecological Preserve. NCCOS Biogeography Branch does not guarantee the accuracy of the geographic features or attributes. Please see the metadata records for each data set for complete information on the source, limitations, and proper use. Disclaimer - While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

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Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; ESRI ArcCatalog 8.3.0.800

Fixed ground control points were selected through examination of imagery, and located in the field. GPS data was collected at each point, and approximately 10-15 points were utilized to orthorectify the imagery. Several additional points were subsequently used to calculate horizontal accuracy:Residuals in meters (root mean square error):1971x: 1.90, y: 1.38 1977 x: 1.83, y: 1.86 Pixel size: 0.5 x 0.5 m

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The composite 1971/1977 mosaic, rather than a single year mosaic, was used because the northward extent and water clarity of photos from any single year were inadequate for overall mapping objectives. Accordingly, areas within the following approximate bounding coordinates originated from 1977 imagery:NE: lon: -64.73161, lat: 17.79139 SE: lon: -64.72022, lat: 17.75467 SW: lon: -64.77546,lat: 17.73921 NW: lon: -64.78095, lat: 17.77758 Mosaicked images were originally photographed at 1:30,000 or 1:20,000, and scanned from diapositives at a resolution of 25 microns, with pixel size of 0.5 x 0.5 m.

These data are believed to be logically consistent, although not tested. Geometry appears topologically clean.