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Header Conventions

The header keys in SEPlib90 are the key to our solution to deal with irregular data. In many cases we will superimpose a grid to ease navigation through a data set (for example we might grid the offset access) , but the main routine will use the higher order of accuracy provided by the header values. SEPlib90 is designed to be as flexible as possible, the user is allowed to create as many header keys, of various types, in any order he wishes. This flexibility is one of the most attractive elements of SEPlib90, but complete anarchy is also unwanted. Without some standards a core set of programs will require an enormous set of user supplied parameters. For example, a NMO routine would require you to supply Such a situation would detract too much from the ease of use that SEPlib is known for. As a result we have reserved certain key names that our core set of programs recognize. To allow ease in transferring from different data types we have based a number of our naming on Colorado School of Mines' Seismic Unix (SU) standards which in turn is based on Barry et al. (1975).

Name Type Description
sx integer Source x location
gx integer Receiver group x location
sy integer Source y location
gy integer Receiver group y location
trid integer Trace status (1= exists 0=padded)
offset integer offset
cdp integer cdp ensemble number
cdpt integer trace number within ensemble

In addition, we have included several other header key conventions that make traversing the data easier, and/or find common use in 3-D processing:

Name Type Description
data_record_number integer Location of trace of given header record
s_x float Source x location
g_x float Receiver group x location
s_y float Source y location
g_y float Receiver group y location
cmp_x float Common mid-point x location
cmp_y float Common mid-point y location
azimuth float Source-receiver azimuth
offset_x float Offset in x location
offset_y float Offset in y location

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Next: UTILITIES Up: DATA FORMAT Previous: Gridding information
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