topcon topf bisf lid shdp is nch vp1 vpn ir esh isa isv ira ita topf =file name of topcon .nez file bisf =file name of Bison file with data lid =line ID shdp =shot depth is =shot location number nch =number of channels (<48) vp1 =geophone location number channel 1 vpn =geophone location number channel nchanl ir =shot record number esh =elevation adjustment to be added isa =source polarization azimuth (deg.) isv =source polarization vertical (deg.) ira =reference polarization R-axis (deg.) ita =reference polarization T-axis (deg.)