Source Position QC offline

This preplot has three sources. Which source fires at the anchored shot is set by the survey's anchored-shot spreadsheet. Load it so the app can check each shot's source and place the SP grid correctly. It is remembered for this survey, so you are only asked once.

Graphs use the current graph settings (inline/crossline view, Y range); the map follows the "Orient to line heading" option.

Which source fires which SP, per line family (from the survey's anchoring spreadsheet). A line belongs to a family when (line − base) is a multiple of step. Sailing with SP increasing ("up"): source = order[(SP − ref) mod 3] or order[(ref − SP) mod 3], as chosen per direction. The rule is used to check each shot's source and to place each line's SP grid so all source positions fall on a common source grid of the given length (in SPs).

Theoretical source position = preplot SP position + offset of the source that fired it. Values are read from the H0900 header lines (preplot first, then production). Crossline is measured perpendicular to the sailing direction, inline along it.

Some preplots give the centre of the sources, others the line one source must shoot on (the other sources are then offset from it). Remembered for this survey.