methods, using RRTS-1 data. Such a provisional map could then 
provide the framework for a ground checking program during the 
field season to follow. Meeting the objective would require that 
the boundaries between the terrain units could be accurately defined 
and, to a lesser extent, that the surface materials could be correct 
ly identified. 
Selected Method of Analysis 
The first group, concerning techniques of visual inter 
pretation, was examined using black and white imagery on all four 
bands, pseudo-colour composites, and several methods of image 
enhancement using variations in assigned-colour densities. This 
group was discarded., not because it did not offer possibilities for 
terrain analysis, but because it could not generate sufficient 
information to construct a suitable terrain map. 
The work, therefore, has been concerned with automated 
techniques of multispectral analysis using the Bendix Multispectral 
Analyzer Display (MAD) unit and PDP 10 computers at the Canada 
Centre for Remote Sensing. 
METHODS 
The criteria used to select the study area were those 
required by the technique to ensure reasonably valid data, that is: 
1) low to moderate vegetation cover, north of the treeline; 2) 
snow-free terrain; 3) high quality data in at least two bands, in 
this case, bands five and six. The area around Pelly Bay, N-.W.T. 
(figure 1) was selected as it most nearly fitted the foregoing 
requirements and from that frame, a small area on the Arrowsmith 
River (figure 2) was used for the study. 
Method of Analysis 
The statistical methods used are those described by 
Shlien and Goodenough (1974) for automated terrain classification. 
Two assumptions were made concerning the validity of the data: 1) 
that any atmospheric distortion of the spectral signatures would 
be constant, and; 2) that because of this, the spectral classes 
assigned to the terrain units would be internally consistent, that 
is, consistent within tne area bounded by the ERT3 frame. 
The technique used was to display a selected portion of 
the ERTS frame on the Bendix and to train on areas of terrain, 
identified, when necessary, by reference to conventional high 
altitude air photography, with a software cursor. It was found 
that using the cursor on full screen classification permitted a 
generalisation of the probably impure terrain units ( that is, 
representing a combination of several spectral signatures) which 
was more suited to pattern recognition than the more precise and 
purer breakdown of units provided by a computer printout of 
pixels. 
By this method, six units were identified, and another 
added for unclassified water areas. The units were: clear water 
with little or no silt content; water with high silt conten ;