Resource Description: The data are being provided on an 'as is' basis. The Corps specifically disclaims any warranty, expressed or implied, including, but not limited to, the implied warranties or merchantability and fitness for a particular use. The entire risk as to quality and performance is with the user. In no event will the Corps or its staff be liable for any direct, indirect, incidental, special, consequential, or other damages, including loss of profit, arising out of the use of these data even if the Corps has been advised of the possibility of such damages. All data are intended for resource management use.
United States Army Corps of Engineers, 20080217, 2007 MrSID Image of St. John Utilized to derive Benthic Habitat Maps (18064_c6_nw.sid): 3001, Inc., 401 Dividend Drive, Suite K, Peachtree City, GA 30269.
This is a Raster data set. It contains the following raster data types:
The map projection used is Lambert Conformal Conic.
Planar coordinates are encoded using Row and Column
Abscissae (x-coordinates) are specified to the nearest 0.304800
Ordinates (y-coordinates) are specified to the nearest 0.304800
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
The purpose of the project is to provide the United States Army Corps of Engineers with current year digital orthophotos covering all of Puerto Rico and the US Virgin Islands. The Corps regularly uses digital orthophotos to support regulatory, land management and acquistion, planning, engineering and habitat restoration projects. The data may also become available to local, state and other federal agencies for their specific management and analysis needs. The one-foot resolution data collected for this project is higher resolution than the previous island-wide collection in 2004, which was one-meter resolution.
3001, Inc., 20080217, Digital Aerial Imagery for 2006-2007 PRVI Orthophotography: 3001, Inc., 401 Dividend Drive, Suite K, Peachtree City, GA 30269.
RLDA, 20070115, Ground Control for 2006-2007 PRVI Orthophotography: RLDA, PO Box 41033, San Juan, Puerto Rico, 00940.
3001, Inc, 20050201, DEM for Orthorectification of 2006-2007 PRVI Orthophotography: 3001, Inc., 401 Dividend Drive, Suite K, Peachtree City, GA 30269.
The triangulated strips were rectified with a recent DEM of the area provided by 3001, Inc. The vertical accuracy of the DEM varies based on the elevation postings and is generally estimated at 30-45cm. The red, green and blue bands were combined to generate a final natural color orthophoto, and the near - infrared, red and green bands were combined to generate a final false color infrared orthophoto.
The ADS40 sensor collects twelve bit image data which requires radiometric adjustment for output in standard eight bit image channels. Converting to eight bit results in a reduction of the color range from 4096 to 256 - thus loss of radiometric detail is inevitable. The extra dynamic range of the sensor permits greater object differentiation in shadows and in bright areas. The sixteen bit dynamic range permitted the imagery to be more effectively color balanced than is possible with eight bit imagery. This was accomplished by performing tonal enhancements immediately prior to the reduction from sixteen bit to eight bit data. In addition to color banancing these eight bit images were adjusted to create seamless imagery to the highest extent practically achievable.
The imagery was mosaicked using a combination of automated and manual seamlines generation. Project pecified tiles were extracted from the mosaic. Final image tiles were reviewed for artifacts and anomalies and adjusted as part of quality control procedures. When necessary, local corrections to the imagery were performed to minimize such effects.
Person who carried out this activity:
(770) 631-0903 (voice)
(770) 631-0820 (FAX)
The accuracy value was determined by measuring photo-identifiable control points collected with GPS survey methods in the orthophotos.
These data cover all of the islands of Puerto Rico, Culebra, Vieques, and the US Virgin Islands. Each orthophoto has an overedge of approximately 30 meters on all sides of its centering 1.875 minute cell.
Sample points taken from overlapping areas of adjacent image strips that contributed image chips to each orthophoto tile are typically consistent to the 2-3 pixel level. This not only ensures that a consistent mosaic can be created from the adjacent image strips acquired with the ADS40 pushbroom scanner but also means that the images have good precision and as a group are spatially self-consistent.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- None. Acknowledgment of the United States Army Corps of Engineers would be appreciated for products derived from these data.
Translation of files to formats other than those described here is the sole responsibility of individuals downloading the data.