First-break picking — g-Platform
First-break picking

First-break picking software

Interactive manual picking and robust semi-automatic picking, in one module, on 2D and 3D projects of any size. Pick in whatever domain suits the data — source, receiver, bin or offset gather — flatten the arrivals with a linear moveout guide, and let the automatic pass carry the picks across the survey while you correct what it gets wrong.

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Manual + automatic
Both in the same module
Any domain
Source, receiver, bin or offset
2D & 3D
Projects of any size
A source gather in g-Platform before first-break picking, beside an empty offset-time QC panel and the source and receiver location map
The same g-Platform source gather with first-break picks marked on the arrivals, and the offset-time QC panel now filled with the picked times
The g-Platform first-break picking workspace: a picked gather, the offset-time QC crossplot and the source and receiver location maps side by side
In view
Before picking
Every refraction solution starts as a set of picks. Statics computed from refractions need the first arrivals as mandatory input, and the quality of those picks sets the ceiling on everything that follows — the regression solution, the tomographic near-surface model, and the stack they eventually sharpen. So the picking has to be fast enough to cover a survey and precise enough to trust. g-Platform answers that with one module that does both halves: automatic picking driven by a moveout guide function, and hand picking on the same gathers with the same parameters. And because a first arrival is a measurement of where the source and receiver really were, the picks double as a geometry check — often the first place a swapped coordinate shows itself.
How picking works

Guide the picker, then correct it.

The automatic picker is not asked to find the first arrival unaided. You give it a linear moveout trend to follow, a search window and a phase to snap to, and it works outward from there — gather by gather, using its neighbours as statistics.

Pick in any sorting domain
Source, receiver, bin or offset gathers — pick on one and edit on another, with the current trace shown in both. The input does not have to be pre-sorted for picking, and the display can be re-sorted without leaving the module.
Linear moveout as the guide
A constant-velocity shift proportional to offset flattens direct waves and refractions. You pick the trend just above the first arrivals and the automatic picker follows it; a time-variant moveout function can be supplied instead of a single velocity.
Manual picking on first energy
Set picks by hand with a search window, a threshold, and a magnet that snaps to the chosen phase or to the type of energy you are picking. Rubber-band a region with the right button and the picks inside it are gone.
Automatic phase tracking
Pick to a nominated phase rather than to a raw amplitude threshold, so later arrivals stay on the same leg of the wavelet. A separate autopicker can re-snap an existing header pick to the strongest local peak of the expected polarity.
Offset-azimuth super-gathers
Build offset classes from an offset step, define the azimuthal directions a 3D survey needs, and pick across an aperture of neighbouring locations while a velocity scan runs from a minimum to a maximum in steps.
Extrapolation across the patch
Existing picks become the guide for the next ones inside a search aperture, so a tuned shot propagates outward rather than being repeated. One action then carries the pass across the entire dataset — which is what makes a large 3D tractable.
Tracking in four dimensions
Picks are interpolated across the survey in x, y, offset and azimuth together rather than gather by gather, which keeps a pick field consistent where the fold and the azimuth distribution change across the patch.
Condition the data as you pick
A filtering sequence can be applied inside the picking process, so the picker works on cleaned traces without the saved data being changed — flatten with moveout, attenuate the linear noise that flattening exposes, then take the flattening back off.
Picking modes

Four ways to set a pick, one set of parameters.

They are not alternatives so much as stages. Most projects tune on one gather, run the automatic pass, then use the guide-line and super-gather modes where the arrivals are weak and manual picking where nothing else will do.

Interactive
Manual picking

Pick and adjust arrivals directly on the current source, receiver, bin or offset gather, inside a manual search window with its own threshold and magnet phase. Picks made on a receiver gather show up on the source gather and the other way round, so the two can be reconciled without leaving the display.

Automatic
Auto picking

Auto-pick the gather in front of you, check it, adjust the automatic window and threshold, and then launch the pass across the whole dataset. The algorithm draws on neighbouring gathers for its statistics, so a full-survey pass is more accurate than the single-gather test that preceded it.

Enhancement
Super-gather picking

Picks are made across an aperture of locations either side of the current one, with a velocity scan between a minimum and a maximum, and the local solver's result fed back to improve them.

Guide line
Solve-guide picking

Pick inside an aperture around picks that already exist, optionally magnetised to a chosen phase with its own window and threshold — the mode that carries a good pick outward into ground that is harder to pick.

Workflow

Six steps from raw gathers to picks you can build on.

1
Read the gathers
Bring in the seismic with geometry already in the headers. Source-receiver sorted data is the usual input, but picking does not require any particular sort order.
2
Pick the moveout guide
Open the moveout window on a source gather and pick a trend just above the first arrivals. Add more trends where the relief or the near surface changes; the picked locations appear on the location map.
3
Tune on one source
Auto-pick the current shot, look at what came back, and adjust the automatic window, the threshold and the magnet phase until that one gather is right.
4
Run the survey
Launch the automatic pass over the whole dataset. Picks generally tighten at this point, because the picker now has neighbouring gathers to lean on rather than one shot in isolation.
5
QC and clean
Work through the offset-time QC maps for sources and receivers, draw a delete line across the outliers and remove what falls inside or outside it — the picks disappear from the map and from the gathers together.
6
Hand the picks on
Solve refraction statics from the picks in place, or export them — in binary for the tomography route — to build a near-surface depth velocity model instead.
QC & controls

Judge a pick field by looking at all of it.

A pick is easy to check on the gather it came from and hard to check across a survey. The QC maps solve that by plotting every pick against offset for a whole aperture of gathers at once, so an outlier stops being one bad trace and becomes a visible departure from a trend.

Picking controls
What the picker is allowed to do
Search windows
Separate windows for manual picking and for the automatic super-gather mode, each with its own threshold, so the two can be tuned independently.
Magnet phase
The phase a pick snaps to, with a magnet type inside the window and an option to find the magnet on click — the control that keeps picks on one leg of the wavelet.
Offset range
Minimum, maximum and step, so unreliable far offsets stay out of the pick field and offset classes can be built for the enhancement modes.
Moveout guide
None, a constant reference velocity, or a moveout function derived from bin-gather picks, with its own start time and velocity.
Azimuthal directions
One by default; on a 3D survey the number of azimuths the picking and the local solver work into is yours to define.
Sliding step
How far the display jumps to the next source or receiver gather, so a survey can be walked at a chosen stride rather than one gather at a time.
QC & geometry checks
What you look at before the picks are used
QC aperture
The radius of gathers each QC map draws at once. A 500 m aperture on a 25 m source interval puts twenty shots' picks in one display; widen it and the coverage gets denser.
Delete line
Drag a band across the QC map, choose remove inside or remove outside, and the picks it covers are dropped from the map and from the underlying gathers at once.
Connected views
Location map, source gather, receiver gather and QC maps stay in step: select a source anywhere and every other window follows it.
Geometry by first breaks
Compare the first-break hyperbola expected from a near-surface velocity against the automatic picks, gather by gather or as an automatic slide show with a delay you set.
Misfit maps
Peak and average misfit, per-receiver-line regression misfits and bad-line counts, coloured onto a map — how a swapped source or receiver coordinate becomes visible.
Export
Write the pick field out for downstream use; the tomographic statics route reads it in binary form.
Modules in this group
The picking and pick-QC modules named on this page — not the full list
Refraction FB picking - azimuthal solver Event autopicker LMO Check geometry by first breaks QC geometry by FB Geometry QC azimuthal
More g-Platform capabilities

Picking is the first measurement the near surface gives you.

The same project, the same batch processing and the same cluster carry a survey from field tape through to depth. These are the other topics in the g-Platform workflow.

g-Platform overview Refraction statics Residual statics Geometry assignment & QC Velocity analysis Stack imaging Signal processing & denoise Multiple attenuation Deghosting, debubble & designature Deconvolution Time imaging Depth imaging FWI & RTM VSP processing Data & geometry formats
FAQ

Questions, answered.

Do I have to pick every shot by hand?
No. The usual route is to pick a linear moveout guide on one or a few source gathers, auto-pick the current source, tune the picking window and threshold until that gather looks right, and then launch the automatic pass over the whole dataset. The automatic picker uses neighbouring gathers for its statistics, so picks improve once it has more than one gather to reason from. Manual picking stays available for the gathers the automatic pass cannot handle, and the same module does both — so the picks and the parameters that produced them never get out of step.
What is the linear moveout guide for?
Linear moveout applies a constant-velocity time shift proportional to offset, which flattens the direct waves and refractions that first-break picking is aimed at. In the picking module it is the guide function for the automatic picker rather than a correction applied to your data: you pick it above the first arrivals on a source gather, and it tells the picker where to look. You can pick as many guide trends as the survey needs — one is enough where the relief is flat — and the module also accepts a time-variant moveout function instead of a single constant velocity.
Can first-break picks find geometry errors?
That is one of their most useful side effects, and g-Platform has two modules built on it. One compares the first-break hyperbola expected from a near-surface velocity against the automatically picked times in each gather and lets you browse the survey gather by gather, or play it as a slide show, watching for the pairs that disagree. The other turns the same disagreement into numbers — peak and average misfit, per-receiver-line regression misfits, bad-line counts — and colours them onto a map, which is what makes swapped source and receiver coordinates or a mis-assigned shot number visible. Both are sensitive to exactly the errors that trace headers alone will not reveal.
Where do the picks go after picking?
Into the near-surface solution. The same module that picks can solve refraction statics directly from the picks, and the picks can also be exported — the tomography route wants them written out in binary — to build a near-surface depth velocity model instead. Both are covered on the refraction statics page. Picks can equally be carried in a trace header and refined later by the event autopicker, which snaps each one onto the strongest local peak of the expected polarity and writes a laterally smoothed version alongside it.
Get started

Pick the first breaks on your own line.

Guide the picker, run the survey, clean the outliers off the QC maps, and take the picks into a statics solution. Talk to Geomage about a demo, or take g-Platform for a trial run.

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