<?xml version="1.0"?>
<!DOCTYPE metadata SYSTEM "http://www.fgdc.gov/metadata/fgdc-std-001-1998.dtd">
<metadata>
<idinfo>
<citation>
<citeinfo>
<origin>
U.S. Geological Survey (USGS);
Stephen P. Teale Data Center
</origin>
<pubdate>1996</pubdate>
<title>$main.title$</title>
<edition>1.0</edition>
<geoform>map</geoform>
<serinfo>
<sername>USGS Digital Raster Graphics</sername>
<issue>
Digital Raster Graphics (DRGs) are scanned color images of USGS
topographic maps.
</issue>
</serinfo>
<pubinfo>
<pubplace>Sacramento, CA</pubplace>
<publish>
U.S. Geological Survey;
Stephen P. Teale Data Center
</publish>
</pubinfo>
<othercit>
Earth Science Information Centers (ESIC) offer nationwide information
and sales service for USGS map products and earth science publications.
For additional information, contact any USGS Earth Science Information
Center (ESIC), or call 1-800-USA-MAPS.
</othercit>
<onlink>http://www.teale.ca.gov/</onlink>
</citeinfo>
</citation>
<descript>
<abstract>
A digital raster graphic (DRG) is a scanned image of a U.S. Geological
Survey (USGS) topographic map. The scanned image includes all map
collar information. The image inside the map neatline is georeferenced
to the surface of the Earth. The DRG can be used to collect, review,
and revise other digital data, especially digital line graphs (DLG).
When the DRG is combined with other digital products, such as digital
orthophoto quadrangles (DOQ) or digital elevation models (DEM), the
resulting image provides additional visual information for the extraction
and revision of base cartographic information. The USGS is producing
DRG's of the 1:24,000-,1:24,000/1:25,000-, 1:63,360- (Alaska), 1:100,000-,
and 1:250,000-scale topographic map series.
</abstract>
<purpose>
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
</purpose>
<supplinf>
Digital raster graphic (DRG) data on CD-ROM are being produced
by the U.S. Geological Survey (USGS) through an Innovative Partnership
agreement with The Land Information Technology Company, Ltd., of
Aurora, CO. This series includes DRG's of USGS standard series
quadrangle maps of the United States, its Trusts, and Territories.
</supplinf>
</descript>
<timeperd>
<timeinfo>
<sngdate>
<caldate>$main.year$</caldate>
</sngdate>
</timeinfo>
<current>ground condition</current>
</timeperd>
<status>
<progress>In work</progress>
<update>As needed</update>
</status>
<spdom>
<bounding>
<westbc>$main.w_b_coord$</westbc>
<eastbc>$main.e_b_coord$</eastbc>
<northbc>$main.n_b_coord$</northbc>
<southbc>$main.s_b_coord$</southbc>
</bounding>
</spdom>
<keywords>
<theme>
<themekt>None</themekt>
<themekey>digital elevation model</themekey>
<themekey>DEM</themekey>
<themekey>digital terrain model</themekey>
<themekey>contour line</themekey>
<themekey>digital contours</themekey>
<themekey>DOQ</themekey>
<themekey>digital orthophoto</themekey>
<themekey>digital orthophotoquad</themekey>
<themekey>digital image map</themekey>
<themekey>aerial photograph</themekey>
<themekey>paper map</themekey>
<themekey>map</themekey>
<themekey>digital line graph</themekey>
<themekey>U.S. Public Land Survey System</themekey>
<themekey>hydrography</themekey>
<themekey>transportation</themekey>
<themekey>topographic</themekey>
<themekey>Universal Transverse Mercator (UTM)</themekey>
<themekey>scanner</themekey>
<themekey>raster</themekey>
<themekey>digital image</themekey>
</theme>
<place>
<placekt>None</placekt>
<placekey>US</placekey>
<placekey>United States</placekey>
<placekey>$main.mapname$</placekey>
<placekey>$main.state$</placekey>
</place>
<temporal>
<tempkt>None</tempkt>
<tempkey>true ground conditions</tempkey>
</temporal>
</keywords>
<accconst>None</accconst>
<useconst>
Acknowledgement of the U.S. Geological Survey would be appreciated
n products derived from these data.
</useconst>
<secinfo>
<secsys>None</secsys>
<secclass>Unclassified</secclass>
<sechandl>None</sechandl>
</secinfo>
<native>Unix</native>
</idinfo>
<dataqual>
<attracc>
<attraccr>
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.
</attraccr>
<qattracc>
<attraccv>00</attraccv>
<attracce>
DRG's are examined to ensure color consistency within a series.
Inspections are performed on selected DRG's to ensure that both the
order of digital numbers (see table 2-2) and digital number values
are correct. Colors will be checked for color compliance to map
series and for major color differences between features on the DRG
and similar features on the source map. Color consistency
throughout each series is checked by comparing a DRG to its
neighboring quadrangles whenever possible.
</attracce>
</qattracc>
</attracc>
<logic>
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.
</logic>
<complete>
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
</complete>
<posacc>
<horizpa>
<horizpar>
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.
</horizpar>
<qhorizpa>
<horizpav>0</horizpav>
<horizpae>
DRG's will retain the horizontal accuracy of the source maps. Most
USGS printed maps contain the National Map Accuracy Standards (NMAS)
note in the collar area. The NMAS states that for maps on
publication scales of 1:20,000 or smaller, not more than 10 percent
of the points tested shall be in error by more than 1/50 inch
measured on the publication scale. Test points must be "well-defined",
that is, easily visible or recoverable on the ground. For
DRG's this accuracy statement applies only to that area of the DRG
that falls within the neatline of the source map (excluding inset
areas). Overedge areas falling outside the transformation boundary
area (the map neatline), can exhibit anomalies or discrepancies.
These anomalies also will appear in the map inset areas and in the
map collar. For maps without the NMAS note, the horizontal accuracy
is unknown. However, the DRG will retain the accuracy of the source
map.
</horizpae>
</qhorizpa>
</horizpa>
<vertacc>
<vertaccr>
In the DRG the vertical positional accuracy is referenced in the DRG
collar.
</vertaccr>
</vertacc>
</posacc>
<lineage>
<srcinfo>
<srccite>
<citeinfo>
<origin>U.S. Geological Survey</origin>
<pubdate>0000</pubdate>
<title>USGS Topographic maps</title>
<geoform>map</geoform>
<othercit>
The source for DRG's are the standard quadrangle format USGS
topographic maps as described in the Federal Geographic Data
Committee "Manual of Federal Geographic Data Products." They
include 1:20,000-, 1:24,000-, 1:25,000-, 1:30,000-, 1:63,360-,
1:100,000- and 1:250,000-scale topographic maps. Included in the
1:24,000- and 1:25,000-scale series are provisional (P) maps and
color orthophotomaps.
</othercit>
</citeinfo>
</srccite>
<typesrc>paper</typesrc>
<srctime>
<timeinfo>
<rngdates>
<begdate>0000</begdate>
<enddate>present</enddate>
</rngdates>
</timeinfo>
<srccurr>ground condition</srccurr>
</srctime>
<srccitea>USGS Topo</srccitea>
<srccontr>
The standard area of coverage of a DRG is the entire area printed
on a USGS standard series topographic map including the map collar,
any overedge areas, and insets. These standard series maps include:

7.5-minute map series: Conterminous United States, Hawaii, and
limited areas of Alaska at 1:24,000 and 1:25,000 scale.

7.5- by 15-minute map series: Covers limited areas of the
conterminous United States at 1:25,000 scale.

30- by 60-minute map series: Conterminous United States
</srccontr>
</srcinfo>
<procstep>
<procdesc>
Production of a DRG begins with the scanning of a paper 7.5-minute
topographic map (map1) on a high-resolution scanner. Scanning
resolutions range from 500-1,000 dpi with an output file of
160-300 Mb in size. Removal of screens (descreening) and color
quantization to reduce the number of colors also takes place during
the scanning phase.

The raw scan file is then transformed and georeferenced using UTM
coordinates of the sixteen 2.5-minute grid ticks, which are obtained
using the in-house produced program COORDAT and stored in a ground
control file. Those sixteen 2.5-minute ticks are interactively
visited and assigned their respective UTM coordinates. The USGS
program XSHAPES4 then performs a piecewise linear rubber sheet
transformation.

An output resolution of 2.4 meters (8.2 feet) is chosen to resample
the file to 250 dpi. The image file is converted to a TIFF 6.0
image and further reduced by converting the file to a run length
encoded PackBits compression (type 32773).

The color palette of the compressed DRG is then standardized by
replacing the original RGB values assigned during the scanning
process with standard RGB value combinations using the in-house
produced TIFFREMAP program.
</procdesc>
<srcused>map1</srcused>
<procdate>0000</procdate>
<proccont>
<cntinfo>
<cntorgp>
<cntorg>
Rolla-ESIC
U.S. Geological Survey
</cntorg>
</cntorgp>
<cntpos>Customer Services Representative</cntpos>
<cntaddr>
<addrtype>mailing and physical address</addrtype>
<address>1400 Independence Rd., MS231</address>
<city>Rolla</city>
<state>MO</state>
<postal>65401-2602</postal>
<country>USA</country>
</cntaddr>
<cntvoice>573-308-3577</cntvoice>
<cntfax>573-308-3652</cntfax>
<cntemail>esic@mcmcmail.er.usgs.gov</cntemail>
<cntinst>URL: http://mcmcweb.er.usgs.gov/drg/</cntinst>
</cntinfo>
</proccont>
</procstep>
</lineage>
</dataqual>
<spdoinfo>
<direct>Raster</direct>
<rastinfo>
<rasttype>Pixel</rasttype>
</rastinfo>
</spdoinfo>
<eainfo>
<overview>
<eaover>
Each raster entity or pixel contains a digital number from 0 through 12
referencing a color palette of RGB values from 0 through 255 in which
the standard colors used in the DRG are defined.
</eaover>
<eadetcit>Standards for Digital Raster Graphic.</eadetcit>
</overview>
</eainfo>
<metainfo>
<metd>19970904</metd>
<metrd>19970904</metrd>
<metfrd>19971230</metfrd>
<metc>
<cntinfo>
<cntorgp>
<cntorg>
Rolla-ESIC
U.S. Geological Survey
</cntorg>
</cntorgp>
<cntpos>Customer Services Representative</cntpos>
<cntaddr>
<addrtype>mailing and physical address</addrtype>
<address>1400 Independence Rd., MS231</address>
<city>Rolla</city>
<state>MO</state>
<postal>65401-2602</postal>
<country>USA</country>
</cntaddr>
<cntvoice>573-308-3577</cntvoice>
<cntfax>573-308-3652</cntfax>
<cntemail>esic@mcmcmail.er.usgs.gov</cntemail>
<cntinst>URL: http://mcmcweb.er.usgs.gov/drg/</cntinst>
</cntinfo>
</metc>
<metstdn>Content Standard for Digital Geospatial Metadata</metstdn>
<metstdv>FGDC-STD-001-1998</metstdv>
<mettc>local time</mettc>
<metac>None</metac>
<metuc>None</metuc>
<metsi>
<metscs>None</metscs>
<metsc>Unclassified</metsc>
<metshd>None</metshd>
</metsi>
</metainfo>
</metadata>