Title:
USDA-NRCS-NCGC Digital Ortho
Originator:
Abstract:
The color infrared (CIR) multispectral compressed county
mosaics in this series were created using Erdas Imagine software. The input images range from 0.15 meter pixel
resolution orthoimage tiles (approximately 6-inch GSD) to 0.6-meter pixel
resolution orthoimage tiles (approximately 2-foot GSD) in GeoTIFF format. The
projected coordinate system is UTM with a NAD83 datum. An orthoimage is remotely sensed image data
in which displacement of features in the image caused by terrain relief and
sensor orientation have been mathematically removed. Orthoimagery combines the
image characteristics of a photograph with the geometric qualities of a map.
All files for the area of interest are processed into a
consolidated mosaic using geo-referencing information from the input images.
The range of compression applied to the mosaics varies from a compression ratio
of 1:10 to 1:25 to save on storage requirements and to accelerate computer
processing and display. All input images must be in the same UTM zone for MrSID
software to create a mosaic. In areas split by a UTM zone, images in the lesser
zone are reprojected to the dominant UTM zone using ERDAS Imagine or similar
software. As appropriate, tone or range adjustments are made to minimize tone
differences between individual tiles and along mosaic seam lines.
These data have been created as a result of the need for
having geospatial data immediately available and easily accessible in order to
enhance the capability of Federal, State, and local emergency responders, as
well as plan for homeland security efforts.
These data are prepared for use by the Natural
Resources Conservation Service for
Format: Raster - MrSID compression, with mosaic
option.
Spatial Reference Information: Universal Transverse Mercator (UTM), North American Datum of 1983
