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The second objective, to convert the large number of existing maps to 
computer-compatible form, presented two conceptual problems. The first 
related to the technology to be adopted for digitizing. While it would 
be possible to digitize data at the photogrammetrie compilation stage of 
map preparation, such equipment is not suited for digitizing existing 
map separates and is overly restricted by the conventions of the current 
mapping process. Some data categories, e.g., boundaries, are not 
obtained from aerial photographs and it was not certain that efficient 
procedures could be developed to allow a plotter operator to capture all 
of the information needed to produce topologically structured data 
files. The second problem is largely economic. Until a sufficient 
number of maps were converted to computer-compatible form, the proposed 
applications would not be realized, and unless the digitizing process 
was rapid and efficient the NMD might incur a large initial investment 
for a data base with few immediate benefits. In economic terras, future 
benefits must be discounted to some degree. 
Thus, the Division has adopted a number of digitizing strategies for 
data capture. Basic to these strategies is a requirement to have a 
rigorously defined archival data file structure for data to be entered 
into the data base. This requirement was necessary to try to avoid a 
plethora of data formats developed only for an immediate application or 
an existing hardware configuration. At the same time, multiple types of 
digitizing equipment were installed and software was developed to pre- 
process the data into the standard format. Manual digitizing tables 
continue to be used and can be quite effective for capture of data cate 
gories consisting of many straight lines or single points. Some manual 
digitizing tables are integral components of interactive editing systems. 
A number of photogrammetric plotters have been retrofitted with digiti 
zers to obtain the usual data categories (such as transportation systems, 
drainage, and contours) that are depicted during compilation of new 
maps. Digitizing was also conducted under contract where automated 
line-following equipment was used effectively. The equipment used to 
prepare orthophotographs has been equipped to simultaneously deliver a 
matrix of digital elevations. Developmental work is underway in the 
area of raster scanning of existing map separates and the editing and 
conversion software needed to change this raw data into the standard 
data base format. 
The third objective, to establish a digital cartographic data base suited 
to geographic information systems, has also presented a number of prob 
lems. Like the chicken-and-the-egg riddle, geographic information 
systems require preexisting digital cartographic data while, conversely, 
a major part of the justification for digitizing maps is to serve large 
geographic information systems that, despite much fanfare, do not appear 
to exist. Many current prototype geographic information systems have 
either a deceiving emphasis on color cartographies but with data of 
marginal quality, or else an emphasis on (expensive) custom-developed 
thematic data without a link to a general-purpose digital cartographic/ 
geographic data base. It appears that a great deal of theoretical 
groundwork has been developed but the actual implementation of geographic 
information systems into a cost-effective range is moving rather slowly. 
The fourth and final objective in the NMD plan is to gradually recon 
figure the conventional mapping process to take full advantage of auto 
mation. The rapidly increasing capability of all types of computers and 
automated equipment coupled with decreasing processing costs (more bits 
for the "buck") makes this a very desirable goal especially in light of 
escalating personnel costs. The previously mentioned perspective that 
led to our delay in producing maps digitally is less true today. Recon-