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Introduction 
This paper outlines the first stage of an air photo based 
study of urban open space which is being carried out in close 
co-operation with the Planning Authority of Merseyside 
Metropolitan County Council. 
With the change in government policy - from building new 
towns on the dwindling supply of agricultural land, to the 
redevelopment of the declining city centres - came the urgent 
need for a systematic and comprehensive inventory of the 
land utilisation of the city centres. 
One important aspect of urban land is the extent and distribution 
of open space, and it is this particular aspect that is the 
subject of the first stage of this research project. 
Figure 1 (The work flow) shows the way in which the project was 
structured in an attempt to satisfy the information needs of 
the Planning Authority. 
The problem was defined as the need to acquire in the most rapid, 
accurate and cost effective manner, details of the open space, 
and present this information in both statistical and map form 
in a way which would be of direct and immediate value to the 
planning authority. The proposed solution was to investigate 
the extent to which aerial photographs might provide the prime 
source material to supply this data. Vertical aerial photo- 
graphs were available at a scale of 1:10,000 in both black and 
white and colour infra red, and comparisons were to be made of 
their relative value for open space surveys. 
The information needs of the Planning Authority dictate the 
type and amount of open space information to be collected: hence 
an essential first step is to define and classify 'open space! 
in relation to these information needs. The first task in 
compiling a notation is to clearly define what is meant by the 
term 'open space!. 
Bearing in mind the applied nature of this study the authors 
worked in close co-operation with the County Planners to ensure 
that the end product of the work would provide the information 
required by them for their particular uses.  '!Open space! was 
defined as: "That land within the urban framework which is not 
covered by buildings". 
The compilation of a notation was based on: 
i) the needs of the planning authority 
ii) the type of information that could most likely be derived 
from black and white and colour infra red aerial photography 
iii) consideration of what other research workers had achieved 
and/or used. 
Figure 2 illustrates the notation finally developed for the 
first stage of this study. The notation contains fourteen major 
units which have been subdivided, mostly on the basis of 
  
     
   
   
  
   
  
  
  
    
  
  
   
   
   
   
  
  
   
  
  
  
   
    
   
   
   
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