At this point, those responsible for data exchange begin to search for a 
"machine independent" data transfer format. The first step is to look at 
existing "standards". There are usually a large number ‚of these, and 
typically the group concludes that they are too complex to implement and/or 
they cannot handle the data to be transferred in a reasonably efficient 
manner. 
It is useful to examine the efforts of various groups which have tackled the 
standardization problem in the remote sensing and GIS communities. However, 
it is important first to define the concepts of data definition and 
information content. 
Data definition information may be recorded in one (or more) of several 
different ways. Three common approaches are: 1) in-line definition of the 
structure of the data fields in the same record; 2) a separate record set 
consisting of a Data Definition Record and its defined Data Records; and 3) 
externally defined data structures. 
The ISO Applications Layer (Layer 7) is intended to carry the information in 
the file, as opposed to the data. In particular, this is the level in which 
the various segments and data fields have been arranged in a desired manner 
by the user in order to convey semantic meaning beyond the structure and 
relationships. The LANDSAT Ground Station Operators Working Group (LGSOWG) 
CCT Format Family and the Standard Formatted Data Unit (SFDU) constructions 
are two of. many examples of attempts to promote the use of similar 
structures for similar data. Each of these provides a defined structure and 
set of rules for assembling the required data fields. 
THE LGSOWG CCT FAMILY 
Because of various hardware restrictions in the first LANDSAT (ERTS) 
processing system, the first NASA-developed CCT format was awkward to use. 
There was little concern for standardization or application of the format to 
other types of data. The format was relatively easy to produce in a high 
throughput product environment, which was the driving force. 
Canada vas the second country to develop LANDSAT processing capabilities. A 
different format was developed. It was a little easier to use than the NASA 
format, but was still specific to Canadian LANDSAT Data Products. 
Because of the close proximity of the two countries and overlap of the 
station coverage, a small group of scientists from NASA, the Canada Centre 
for Remote Sensing (CCRS) and the U. S. Geological Survey (USGS) met in the 
early 1970s to define a nev, common format. The group learned about a data 
format which had been developed by NASA's Johnson Space Centre (JSC) for 
recording airborne image data. The format was found lacking in several 
respects for LANDSAT data. However, through negotiations with those at JSC 
responsible for maintenance of the format standard, it was possible to 
expand the definition to satisfy the LANDSAT MSS and RBV data transfer 
requirements. 
CCRS adopted the modified JSC standard not only for LANDSAT data but also 
for its own aircraft image data systems (Strome et al., 1975). Brazil had 
already adopted the original NASA format and could not easily change. The 
European Space Agency, however, adopted the new format. It was virtually 
accepted as the standard by the LGSOWG when it was discovered that NASA and 
USGS had let a contract to define the format to be used by the EROS Data 
Centre for provision of CCT data as this operation was transferred from 
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