U.S. Geological Survey EROS Data Center , 1996, Digital Raster Graphics (DRGs): USGS Digital Raster Graphics Digital Raster Graphics (DRGs) are scanned color images of USGS topographic maps. , U.S. Geological Survey EROS Data Center , Sioux Falls.Online Links:
This is a Raster data set. It contains the following raster data types:
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The DRG is used for validating digital line graphs (DLG's) 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 DRG's
and DOQ's for revising and collecting digital data, DRG's and
DEM's for creating shaded-relief DRG's, 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, 0000, USGS Topographic maps.
Person who carried out this activity:
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The DRG uses a standard palette to ensure uniform color
throughout a particular map series. The RGB values for a particular
color, therefore, will remain consistent throughout that DRG series.
Although the color values of the DRG may sometimes match those
of the paper source map, a user will usually notice small differences
between the colors on the digital image and on the paper map. Also,
the quality of the user's monitor affects the DRG color displayed.
Although the DRG generally contains the complete content of the
source map, features may occasionally be blurred because of
substandard source materials. The DRG also may contain
misclassified pixels (color noise).
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 DRG's will be accuracy tested. The accuracy
test will be performed by comparing the positions of UTM grid
intersections on the source graphic against the corresponding
location on the digital image. A visual inspection will determine
whether those coordinates fall within the pixels that define a grid
tick. DRG's duplicate the horizontal accuracy of its source.
In the DRG the vertical positional accuracy is referenced in the DRG
collar.
Image completeness is checked by visually inspecting a sampling of
DRG's. Each selected DRG will be 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
- Use_Constraints:
Acknowledgement of the U.S. Geological Survey would be appreciated
n products derived from these data.
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DRG CD-R
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. The USGS will warrant the
delivery of this product in computer-readable format and will offer
appropriate adjustment of credit when the product is determined unreadable
by correctly adjusted computer input peripherals, or when the physical
medium is delivered in damaged condition. Requests for adjustment of
credit must be made within 90 days from the date of this shipment from
the ordering site.
| Data format: |
To facilitate file manipulation by the widest possible range of potential users, data and text files on the CD-ROM conform to the DOS "eight plus three" (8.3) file naming convention. The associated DRG image (.TIF), world (.TFW), and metadata (.FGD) files incorporate an intelligent data set name (DSN) consisting of descriptive metadata wrapped around a standardized kernel that describes the spatial location of the file. The intent of this file naming protocol is to positively identify the spatial identity of the file and describe its categoric identity. The DSN is designed to geographically locate DRG's of quadrangles using the 7.5-minute grid, clearly identifying those that fall exactly on the grid. DRG's that are not aligned with the 7.5-minute grid can be named with this convention but additional consideration is required to relate these undersize, oversize, or offset quadrangles to their most logical and unique 7.5-minute grid location. in format Tagged Image File Format (TIFF) (version version 6.0) Download WinCATS USGS DRG and DLG-O & DRG viewing software available from USGS. Size: 5 to 15 megabytes. |
|---|---|
| Media you can order: |
CD-ROM
(Density 650
megabytes)
(format ISO 9660)
Note: None
|
The current costs are available at: URL: <http://edc.usgs.gov/glis/hyper/order_info/prices#DRG_CD> DRG File size may necessitate distribution on multiple CD-ROMs
Dataset searching and ordering capabilities are available through the
Global Land Information System (GLIS) at:
URL: <http://edc.usgs.gov/webglis>
ASAP
Adobe Acrobat Reader 2., CD-ROM drive
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