Sub-disciplines under Earth Sciences 
Atmosphere 
32% 
    
Interior and Crust 
8% 
Land 
25% 
Ocean 
35% 
  
  
  
Figure 2 Distribution of the Earth Sciences 
datasets among the sub-disciplines Land, 
Atmosphere, Ocean and Interior & Crust. 
When a dataset of interest has been identified the 
user can automatically connect to data systems 
and catalogues in Canada and around the world. 
The development of the Directory service is 
based on catalog interoperability concepts which 
have been developed by the Committee on Earth 
Observation Satellites (CEOS) and widely 
endorsed by the international science 
community. This compatibility ensures that 
GCNet will provide Canadian users access to 
international datasets which are critical to global 
change programs [2]. 
¢ Inventory Service 
GCNet also supports an Inventory service which 
provides access to an image inventory data base 
describing all the satellite data in the CCRS 
archive. The database contains records of 
approximately 1 million scenes which have been 
archived at CCRS since 1972. All future satellite 
data archived by CCRS, such as RADARSAT 
data processed on CCRS FASTSCAN [6] 
system, will be added to this data base. 
The GCNet Inventory Service is provided by the 
CCRS QUERY program. QUERY provides the 
capability to search the Image Inventory data 
base which describes the CCRS data archive 
holdings. This capability is essential in view of 
the large volume of data presently available 
(Table 1). 
Table 1 CCRS satellite data archive content for 
the period between July 1972 and February 
1994. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Landsat MSS 387,000 
Landsat TM 106,000 
SPOT (Multispectral) 135,000 
SPOT (Panchromatic) 316,000 
MOS MESSR 31,000 
SEASAT SAR 462 
ERS-1 SAR 107,000 
"TOTAL | 976,174 
  
  
  
QUERY provides the following image inventory 
search capabilities: 
i) Selection of geographical area either by: 
Lat/Long rectangular box or Track/Frame 
rectangular box. 
ii) Selection of scenes based on any logical 
combination of the following fields: 
satellite identifier 
sensor identifier 
sensor mode (if applicable) 
view angle (if applicable) 
acquisition date 
cloud cover 
iii) Multi-inventory searches: i.e. the capability 
to do searches in many satellite/sensor 
databases from a single user session. 
For ease of consultation, the QUERY search 
results, in a tabular report format, can be e- 
mailed to th 
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