preservation of accuracy and information; 
machine and language independence; i 
simple to use (but need not be simple to implement); taie 
allow for self-defining format (i.e., permit blind transmission) or very 
simple format (no definition); 
modular and easily extensible to handle new types of data, projections, 
etc. 
To produce tangible standards in a reasonably short time frame, the 
Committee decided to focus on the folloving: 
topographic data which can be represented on maps as point, line and area 
features, all of which may have attributes or text, and spatial 
relationships; 
a general Digital Topographic Information Model (DTIM) expandable to 
include as a second priority thematic data (e.g. forestry, cadastral, 
etc.) with locational and attribute components and spatial relationships; 
not to deal with image, grid or raster data; 
not to deal with cartographic representation or symbolization aspects of 
topographic data. 
Several standards were examined, including the LGSOWG, SDTF, and ISO 8211. 
The LGSOWG family were deemed unsuitable as they were optimized for image 
data, and the mixture of ASCII and binary data violates modern approaches to 
standardization. It was felt that the ISO 8211 was far too general, and 
thus complex for the purposes of the group. 
In 1982, the American Congress of Surveying and Mapping was chartered by the 
USA National Bureau of Standards to develop common formats for the various 
cartographic objects used in digital mapping. To achieve this goal, it 
founded the National Committee for Digital Cartographic Data Standards 
(NCDCDS). Several reports have been prepared and widely distributed 
(Moellering, 1985a, 1985b, 1985c). It has been recognized by this committee 
that images are a form of cartographic data, and thus image modules have 
been defined in a structure compatible with the family of polygon, line, 
point and other cartographic files currently being defined. It has examined 
several alternate file structures, including the Canadian Spatial Data 
Transfer Format (SDTF), the General Data Interchange Language (Billingsley, 
1986) and ISO 8211 (ISO, 1985). The SDTF has been rejected by the Committee 
as a candidate, as it does not follow the current standards philosophy. In 
particular, the mixture of ASCII and binary data in header records is no 
longer generally acceptable. 
ISO 8211 - A DATA DESCRIPTIVE FILE FOR INFORMATION INTERCHANGE 
The ISO standard is a transmittal format standard, to be used for any set or 
structure. As such, it defines the data coding and logical structures. It 
expects further standard ISO labels. 
The intent is to allow data structures to be easily moved from one computer 
system to another, independent of type. The standard specifies 
medium-independent and system-independent file and data record formats. It 
is intended to apply to physical media as well as communications media. The 
standard is intended for information interchange only, and is not intended 
to be used for general processing. The basic approach used is to map the 
sender’s information, including file structures such as sequential, 
hierarchical, relational, and indices, to the interchange format. The user 
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