I 
ACQUISITION OF DIGITAL TOPOGRAPHIC DATA 
AND THE 
NEED FOR A STANDARDIZED DIGITAL DATA BASE 
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Dr. M. Mosaad Allam 
Topographic Survey Division 
Surveys and Mapping Branch 
Department of Energy, Mines and Resources 
615 Booth St., Ottawa 
Canada K1A 0E9 
ABSTRACT. 
With the increasing use of computer-based digitizing units, there has 
been a strong and welcome trend towards the production of digital 
topographic data by means of: (1) digitizing photogrammetrically- 
produced graphic plots using manual digitizing tables, semi-automatic 
line following systems or automated raster scanning systems, and (2) 
direct photogrammetric instruments interfaced to digital computers. The 
various systems and techniques used in the acquisition phase of digital 
topographic data are described. With the completion of this phase, the 
compiled digital data is stored in a latent state, until the information 
necessary to satisfy a specific demand is called for, at which time the 
automated output system produces it in the form required. 
The successful conversion of the data from a quiescent to active state, 
requires the development of a comprehensive data base. This is an 
integral part of the data collection process either during digitizing or 
separately, depending on the level of sophistication and interaction 
needed with the data base. The essence of the data base is to provide 
an information base from which a variety of information as well as 
graphic products may be produced upon demands. The paper discusses the 
design concepts of the National Digital Topographic Data Base developed 
in Canada for the exchange of digital topographic information among 
various users. 
INTRODUCTION 
The increased appreciation of the advantages of map data in digital form 
is accelerating the application of digital mapping and automated 
cartography. Numerous government mapping agencies (at various levels), 
institutions and private industry throughout the world are actively 
engaged in computer-aided map compilation and production. This is 
basically done to achieve higher level of efficiency, cost effectiveness 
and improved responsiveness in the production of maps, charts and 
related information. 
This noticeable acceptance of the advantage of map data in digital form 
is attributed to numerous reasons including: 
- with digital technology, computational processing, drafting and 
scribing, changes of scale and projections can be achieved at a 
fraction of the manual cost,