pression is not 
ymputers. 
reduces the 
‘ale DRG to 
egabytes. 
available in 
er Standard 
996. 
compliant with 
hic Data 
standard, will 
| set. Metadata 
eparate physical 
S OF DRG's 
new, it is 
for how long, 
3IS community. 
inly to provide a 
appealing 
or data. Like 
rom which they 
rnish consistent 
untry. 
d with other 
c data. Shaded 
uickly and 
3s with digital 
Digital 
iade by 
ound and area 
| combining the 
0S. 
Revision 
can be digitized 
computer 
fective for such 
5. For most 
reen digitizing 
alternative to 
scanning or table digitizing, both of which 
require more equipment and training. The 
DRG combined with a digital orthophoto- 
quad image can be used to combine vector 
collection with monoscopic revision. The 
combined image significantly reduces total 
collection time by contrast to a two-step 
process of collection from a graphic 
followed by revision from imagery. 
DRG's can be used for some types of 
vector data quality control by allowing fast 
visual comparisons between a map and 
derived vector data. For some data 
categories, spatial accuracy of nonbase 
data can be verified by overlaying vectors 
on a DRG base map. 
3.3 On-line Indexes and Catalogs 
The USGS is developing a network- 
accessible system for display and ordering 
of products. Digital map indexes are 
seamless and can display more product 
information than paper indexes. 
Appropriate filtering of DRG data 
produces a map image small enough to be 
transmitted over the network (typically 
several hundred kilobytes in GIF format), 
while retaining enough quality to make a 
full quadrangle image visually appealing. 
This DRG browse image allows users to 
preview maps quickly and easily. 
4. USGS DRG PRODUCTION AND 
DISTRIBUTION 
Mass production of USGS DRG's will be 
accomplished using an Innovative 
Partnership. Production is expected to 
start in the late summer of 1995. 
4.1 Map Series and Production Schedules 
DRG's will be made of standard USGS 
quadrangles at 1:24,000,1:25,000, 
1:100,000,1:250,000 and (Alaska only) 
1:63,360scales. The order and rate of 
production will be driven by user 
29 
requirements and by partnerships with 
Federal and State agencies. 
Although requirements of other Federal 
agencies are not fully documented at this 
writing, full coverage of the contiguous 48 
states likely will be achieved in 1995 for 
1:100,000- and 1:250,000-scale maps. Full 
coverage at 1:24,000 scale is expected in 
about 3 years. 
Investigations into making DRG's of 
nonstandard maps are just beginning. The 
raster graphic concept extends easily to any 
kind of map, and DRG's of thematic and 
historical maps will become important. 
The Library of Congress is currently 
exploring options for producing DRG's of 
its historical maps. 
4.2 Product Packaging and Distribution 
DRG's will initially be distributed on 
CD-ROM. Each CD will include technical 
and user documentation in addition to the 
DRG data and metadata. The data will 
initially be packaged in regularly shaped 
blocks; for example, 1-degree squares 
(64 quadrangles) for 1:24,000-scale data. 
Network distribution for some types of 
product orders is being considered. 
The USGS will also make DRG's available 
in SDTS format in 1996. The distribution 
media for these data have not yet been 
determined. 
4.3 Contracted Production 
The USGS plans to produce nationwide 
coverage for placement into the public 
domain using an Innovative Partnership 
agreement with Land Information 
Technology Company, Limited (LandInfo), 
of Aurora, Colorado. This agreement is 
the first of its kind between the USGS and 
the private sector.