How sioseis process geom
calculates rp numbers

According the process geom documentation (22
October 2002)

The shot is assigned an
X-coordinate by adding (type 1) or multiplying

(type 2) DFLS (distance from
the last shot) to the X-coordinate of the

shot. Each receiver is assigned an
X-coordinate by adding the

shot-receiver distance to the
shot X-coordinate. The RP X-coordinate

is calculated by assuming the
RP is halfway between the shot and

receiver. The RP number is the RP X-coordinate divided
by DBRPS

(distance between RPs) and
truncating to an integer. The
coordinate of

the first shot of the job is
the shot number (from the header) times the

distance from the previous
shot. i.e.

xs = FLOAT(lhead(3)) * dfls

rx = FLOAT(lhead(10))

xr = xs + rx

xrp = (xr + xs) / 2.

lhead(6) = NINT( xrp/dbrps )

Type 2 geom example where the
first shot is shot 9711, dfls = 50,

dbrps = 6.25, range to trace
1 = -6168:

xs = 9711. * 50. = 485550.

rx = -6168.

xr = 485550. -6168. = 479382

xrp = (485550 + 479382.) / 2.
= 964932/2 = 482466

rp_number = 482466 / 6.25 =
77194.56 = 77195

Type 9 geom example where the
first shot is 33000, dbrps = 6.25, and

range to trace 1 = -6168:

(type 9 geometry sets dfls =
1. for the first shot)

xs = 33000.

rx = -6168.

xr = 33000 -6168 = 26832

xrp = (33000 + 26832) / 2 =
59832 / 2 = 29916

rp_number = 29916 / 6.25 =
4786.56 = 4787

Type 9 geom example where the
first shot is 58309, dbrps = 6.25, and

range to trace 1 = -6168:

xs = 58309

xr = 58309. -6168. = 52141.

xrp = (58309. + 52141.) / 2.
= 110450. / 2. = 55225.

rp_number = 55225. / 6.25 =
8836