SUPACK1 - pack segy trace data into chars

supack1 <segy_file >packed_file gpow=0.5

Required parameters:
none

Optional parameter:
gpow=0.5 exponent used to compress the dynamic
range of the traces


Credits:
CWP: Jack K. Cohen, Shuki Ronen, Brian Sumner

Caveats:
This program is for single site use. Use segywrite to make a portable tape.

We are storing the local header words, ungpow and unscale, required by suunpack1 as floats. Although not essential (compare the handling of such fields as dt), it allows us to demonstrate the convenience of using the natural data type. In any case, the data itself is non-portable floats in general, so we aren't giving up any intrinsic portability.

Notes:
ungpow and unscale are defined in segy.h
trid = CHARPACK is defined in su.h and segy.h

Trace header fields accessed: ns
Trace header fields modified: ungpow, unscale, trid