Title:
USDA-NRCS-NCGC Digital Ortho
Originator:
Abstract:
The black and white or grey scale single band compressed county
mosaics in this series were typically created using Erdas
Imagine software from 0.6-meter pixel resolution (approximately 2-foot GSD) orthoimage tiles 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.
Purpose:
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
