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The first step in such an approach (after North 1971) is to define the area or 
areas to be surveyed and then to collect whatever environmental data are already 
in existence. While this ground truth data is being collected, a set of high 
quality aerial photographs of the study area should be flown. From this imagery 
skilled photo-iuterpreters would prepare land use maps. By measuring areas, it 
is possible to determine how much land is devoted to each activity. When these 
steps have been completed, the specific information can be extracted concerning 
the detection, identification and monitoring of environmental pollutants. 
Relevant information must be gained from the phoicgraphy to serve both as a base 
line against which to monitor subsequent changes and for taking and impiementing 
planning decisions. By careful examination of the photography, interpreters can 
be helped to carry out cataloguing and inventory of effluents, sewage plant 
location, smckestack plumes, etc., thus, a base map of pollution sources and 
indicators can be compiled. Once the basic photographic coverage has been 
analysed, the requirements for further photography will become obvious. It is 
at this point that specific sensors, altitudes and film/filter combinations will 
be required. 
The next step in determining environmental quality is to build up an information 
system and working model of the region. This involves the use of a conputer to 
store the available environmental information. One method is to digitise the 
photo-interpretation map overlays on the basis of grid cells, thereby facilitating 
data extraction and comparisons with subsequent data sets. Another method is to 
code and store the data so that it can be related to enumeration districts, 
allowing the data to be correlated with other census information. Thus, remote 
sensing is a systematic approach, which facilitates the future use of data for 
other purposes. Each new set of data may be entered and compared with previously 
collected information. 
The final stage in such a regional environmental quality study is to initiate 
corrective programmes. This involves decisions which must be made by adminisurytors, 
resource managers, ecologists, planners etc. Once corrective actions have been 
taken, it is usual to monitor the region to assess improvements. This, of course, 
can also be accomplished by remote sensing methods. Thus, if periodic coverage 
is acquired it can be used not only to produce new data but to assess the success 
or failure of the corrective programme. 
Environmental studies now play a major role in all phases of construction planning 
and operation. Collection of data necessary to establish base-line environmental 
conditions, as well as studies to determine the extent of impacts from existing 
facilities require massive field investigation programmes. Remote sensing 
technology provides an efficient and systematic approach to environmental data 
collection and field survey planning. The advantages of the modern remote 
sensors lie not only in the synchronous and synoptic observations of phenomena 
of regional studies, hut in the combination of results from various sources, 
aerial photography, imagery, computer data and field work. There will no doubt 
be cases where the use of any one method will satisfy the demands made on 
individual research projects. However, the multi-informational remote sensing 
systems, where interpretation from the various sources is undertaken by inter- 
disciplinary working groups, will provide the best over-view of the environment.