- 1340 - 
A number of engineers questioned various aspects of the use of a grid 
pattern for model description and the definition of the network.  Propo- 
sals were made which would either refine the present computations or 
increase their flexibility. The following is a complete list of proposed 
modifications:- 
1) Changing the shape or size of the grid. 
2) Allowing movement on diagonals as well as forwards and side ways. 
3) Utilizing the table of nodes passed through by each alternative 
to search and tabulate the conditions, such as soil types, land 
use categories, etc., encountered by each choice. 
4) Modifying or adding methods of ranking the alternatives. 
5) Modifying the central percentage of links (originally set at 932) 
being removed from consideration before generation of the next 
alternative. 
6) Allowing for the optional complete removal of centain links in 
the network to prevent travel across certain areas. 
7) Allowing the retention of certain links in "control sections" 
so that many choices can utilize a bridge or tunnel crossing site. 
These evaluations continued in Canada, the United States and Europe 
(Figure 1) between 1971 and 1974. 
The GMAPS-GCARS System 
The GMAPS Programs 
In 1973 work began on a new system of programs which would incorporate 
improvements suggested by the experience gained in use of the earlier 
systems. The needs for environmental impact assessment required the 
development of much more sophisticated data base manipulation systems 
which addressed the needs for flexibility, speed and economy, compre- 
hensitivity, and increased quantification of data and conclusions. 
The GMAPS System computer programs were designed to address these needs. 
À cellular mapping format was selected because such a system appeared 
attractive to many government and private users. Cellular mapping 
techniques had been applied experimentally to several studies in the 
western states. Because considerable investment had been made on data 
bases for such systems, GMAPS was designed for data compatability with 
these. GMAPS differed from these existing, batch operated systems by 
virtue of its interactive, self prompting operation. This makes GMAPS 
very attractive to use because: 
1) the programs are self prompting; they ask a sequence of questions 
to which the user responds thereby defining the operations and 
sequence of operations the user wishes to perform; 
2) the programs allow the user to verify and correct commands, so 
that meaningless operations are eliminated; 
3) the system is easily used by laymen; 
4) the time sharing concept gives the user economical access to 
a high capacity computer. 
The GMAPS programs utilize a composite computer mapping technique. Com- 
posite mapping has traditionally been a manual procedure involving the