INTRODUCTION 
The method reported here is a continuation of earlier work 
which determined the approximate numbers of livestock on dairy 
or beef farms in southern Ontario. (Ryerson 1971). A short 
discussion will be presented on a different approach to visual 
interpretation and the application of this new approach to an 
agricultural problem. 
An attempt will be made to obtain the dollar output per 
individual farm from the method's application to 1:15 840 pan 
chromatic imagery; this will be based on estimated crop, live 
stock, and milk products produced. 
APPROACH TO INTERPRETATION 
The approach used and the consequent results are founded 
upon the author's methodological position which may be summarized 
by four statements: 
1. Interpretation procedures can be further developed 
for the most simple imagery types. 
2. The most consistent and accurate interpretations 
result from logical, reproducable methods. 
3. Logical procedures are as useful for specialized 
interpreters as for inexperienced interpreters. 
4. Quantifiable guidelines may be developed for the 
analysis of both spectral (tone) and spatial (pattern) 
elements of imagery. 
The aerial photograph and most other remote sensing output 
may be regarded as two dimensional (spatial) data sources. 
Photographic stereopairs yielding height information are three 
dimensional data sources. These data could be considered as 
additional dimensions, although they are related to the frame 
work provided by the first two or three dimensions. 
In order to obtain relevant information the interpreter 
essentially 'questions' the data source, or image. (IS THIS WHAT 
I AM LOOKING FOR? IS THIS A, OR B, OR SOMETHING ELSE?"). It 
is obvious that the way in which the image is questioned or 
interpreted is very important in the analysis of the features of 
interest on the image. 
Two approaches to questioning an image are identified here: 
1) unstructured, and 2) structured. These correspond respectively 
to interpretation based on the user's prior knowledge of reference 
level (vink 1964) and interpretation or air photo reading using