-01570.- 
he most promising satellite MSS data for multitemporal studies of 
earth resources can only be obtained if careful consideration is given to the followin 
factors (Figure 2): cloud cover, image quality, snow cover, bio-climate 
(soil moisture), vegetation/crops and sidelap. The above factors are 
important for both visual interpretation as well as digital analysis of 
Landsat MSS data. 
The selection and ordering of Satellite MSS data for earth resources 
surveys is a time consuming process, taking six to eight weeks (depending 
on postal services and customs clearance) for a non-US resident even 
when the order is placed at the most efficient of all distribution centres 
EDC, USA. In Europe, airmail parcels valued at less than $ 100 
generally meet with no delay during delivery. 
Landsat reference systems, maps, catalogues and micro fiches 
The US Geological Survey has published in 1975 a series of 1:9 million 
and 1:18 million Landsat maps covering the whole world with five cloud 
cover classes. The World Bank issued a Landsat Atlas (1976) of the 
Developing Countries of the World, in which Cuba and China have been 
omitted together with Western Europe and the USSR, but countries like 
Ireland, Spain, Israel and Iran, to mention just a few, have been included. 
Telespazio, Italy,and the Instituto de Pesquisas Especiais (ENPE), Brasil 
have issued maps with path and row number of the area over which they 
can receive Landsat MSS data in real time. One may conclude that existing 
maps and catalogues provide partial and out-of-date information on 
available imagery. 
Two new reference systems that will provide users with quick and inexpensive 
access to Landsat data have been developed by the EROS Data Center with 
support from the National Cartographic Information Center. 
Called the Landsat micro-catalog and Landsat micro-image systems, these 
products use standard microfiche records to replace the paper catalogues 
and roll microfilm of 'browse' images that were previously the basic tools 
tools for Landsat information (Landsat Users Note, No. 2, May 1918). 
A subscription to one of the above reference systems is of great use to 
major customers requiring areas which are not covered by Telespazio & 
INPE. 
  
  
  
  
  
  
  
   
  
   
  
  
  
   
   
   
   
  
  
  
  
  
  
  
  
  
  
  
   
  
  
   
  
  
  
   
  
  
  
    
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