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Abstract

Digital Raster Graphics are provided online by the California Spatial Information Library (CaSIL)

The Digital Raster Graphic (DRG) is a raster image of a scanned USGS topographic map including the collar information. The source maps for DRGs were georeferenced to the UTM grid, but images DRGs for California are available in Albers equal area projection, see the projection information.

A DRG is useful as a source or background layer in a GIS, as a means to perform quality assurance on other digital products, and as a source for the collection and revision of DLG data. DRG's can also be merged with other digital data, e.g. DEM's or DOQ's, to produce a hybrid digital file.

Series Information

There are multiple series of DRGs for different scales. The 1x2 degree series are at a scale of 1:250K. The 30x60 minute series are at a scale of 1:100K, and the 7.5 minute series are at 1:24K. Additionally, there are some 1:25K scale maps that are included in this distribution as belonging to the 7.5 minute series.

For the 1x2 degree series, there are 41 images covering the state of California and immediately adjacent areas. These DRGs were originally obtained from the California Department of Fish and Game (DFG).

For the 30x60 minute series, there are 127 images covering the state of California and immediately adjacent areas. These DRGs were originally obtained from the California Department of Fish and Game (DFG).

For the 7.5 minute series, there are 2853 images covering the state of California and immediately adjacent areas. Statewide DRG production was performed by the State of California, Stephen P. Teale Data Center, GIS Solutions Group (Teale). Additional acknowledgments include: Governor's Office of Emergency Services (OES): compilation of DRG quad dates and other attributes; California Department of Fish and Game, Information Technology Branch: non-standard quad boundaries, quad currentness year information and enhanced index compilation.

Obtaining DRGs

All California Digital Raster Graphics are available on CaSIL at http://casil.ucdavis.edu/casil/gis.ca.gov/drg, or via the interactive map interface.

In addition, the DRGs are mirrored at: http://casil-mirror1.ceres.ca.gov/casil/gis.ca.gov/drg/. Also, there is an additional web interface available at http://ims.gis.ca.gov/website/casil/drgquads/viewer.htm.

The map identifiers are organized into 1x1 degree blocks covering the state. Within these blocks individual maps, and ancillary data are located.

News Items

New Map Interface
waylandyu - 2004-03-30 10:06 Digital Raster Graphics
We are pleased to unveil a new map interface, based on USGS Mapsurfer technology, that now allows you to browse the DRGs (previously you were only shown the DRG boundaries), in addition to downloading the datasets. You can access the interface at:

http://drg.casil.ucdavis.edu/mapsurfer/


New NAD83 DRGs
waylandyu - 2004-03-30 10:06 Digital Raster Graphics
We have upgraded our DRG library to include NAD83 trimmed/untrimmed versions of the DRGs, as well as NAD83 mosaics. As always, you can access the new datasets at:

http://casil.ucdavis.edu/casil/gis.ca.gov/drg/


New Access Methods
qjhart - 2002-Jul-11 16:15 Digital Raster Graphics
A minor modification was made to the site allowing for indexing of the datasets by name, and pointing to NASA as a Mirror site. and Berkeley for a new map interface.
1:100K Trimmed Versions Available
qjhart - 2001-Dec-05 09:06 Digital Raster Graphics
The 1:100K (f-series) maps are now available online.
1:24K Trimmed Versions
qjhart - 2001-Nov-27 16:06 Digital Raster Graphics
The trimmed versions of the 1:24K (o-series) maps are now online.
DRG website online
qjhart - 2001-Oct-11 17:54 Digital Raster Graphics
A preliminary website for the California Digital Raster Graphics is online.

This website still needs review, some graphics, and a better package for the distributed ftp sites.
1:24000 Scale DRGS online
qjhart - 2001-Aug-28 14:16 Digital Raster Graphics
The 1:24000 scale DRGs have been made available via the anonymous ftp site at: ftp://casil.ucdavis.edu/casil/gis.ca.gov/drg.

Only the untrimmed versions of these files are currently available.
Access news items from the Digital Raster Project at casil.ucdavis.edu

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