USGS Earth Resources Observation and Science Center (EROS), 19981101, Digital Raster Graphic: TETON VILLAGE , WY: USGS Digital Raster Graphics Digital Raster Graphics (DRGs) are scanned color images of USGS topographic maps., USGS Earth Resources Observation and Science Center (EROS), Sioux Falls.
This is a Raster data set. It contains the following raster data types:
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 2.438400000000
Ordinates (y-coordinates) are specified to the nearest -2.438400000000
Planar coordinates are specified in meters
The horizontal datum used is North American Datum 1927.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.98.
The DRG is used for validating digital line graphs (DLGs) and for DLG data collection and revision. The DRG can help assess the completeness of digital data from other mapping agencies. It can also be used to produce "hybrid" products. These include combined DRGs and DOQs for revising and collecting digital data, DRGs and DEMs for creating shaded-relief DRGs and combinations of DRG, DOQ, and DLG data. Although a standard DRG is an effective mapping tool, its full potential for digital production is realized in combination with other digital data.
U.S. Geological Survey, 19981101, Digital Raster Graphic: TETON VILLAGE , WY.
Person who carried out this activity:
+001 573-308-3577 (voice)
The DRG is an 8-bit color image that employs a color palette to ensure uniform colors throughout a particular DRG series. All DRG's within a series must have the same RGB value.
A random sampling of DRGs is accuracy tested. The accuracy test is performed by comparing the positions of UTM grid intersections on the source graphic against the corresponding location on the digital image. A visual inspection determines whether those coordinates fall within the pixels that define a grid tick. DRGs duplicate the horzontal accuracy of its source.
The vertical positional accuracy of a DRG is referenced in the DRG collar
Image completeness is checked by visually inspecting a sampling of DRGs. Each selected DRG is examined for gaps (missing data) in the main body of the map, the map collar, the overedge areas, and any insets.
The USGS DRG is produced with the intention of replicating as close as possible the original source map. Users of the DRG will note, however, that a certain amount of "noise" can be discerned when small areas are blown up or viewed under zoomed-in conditions. This noise is in the form of random specks or pixels of color and halos due to any number of factors, such as the quality of the source, the use of screens and patterns on the litho, and the unevenness of ink due to saturation and absorption. Discontinuities or breaks in linear features may also be present and are due to improper calibration or usage of the scanner, the condition of the source, and resampling. Descreening, quantizing, and noise filtering are methods used to reduce noise, which, besides creating a more aesthetically pleasing image, have the added benefit of reducing the size of the image file. Removal of lithographic screen patterns is preferred but not required.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Acknowledgement of the Geological Survey would be appreciated in products derived from these data.
Although these data have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made by the USGS regarding the use of the data on any other system, nor does the act of distribution constitute any such warranty.
|Data format:||TIFF (version version 6.0) Download WinCATS USGS DRG and DLG-O and DRG viewing software available from USGS.|
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