The Grid velocity by markers + horizons method uses the same marker-horizon ties and the same wizard inputs as the Markers + horizons method, but writes the result on a bin grid rather than on the native trace grid of the horizons. Use it when downstream tools need a regular, bin-aligned velocity volume.

Required inputs

• Datum — elevation reference.
• Marker-to-horizon tie table — time horizon + marker/group pairs; same structure as in Markers + horizons.

Parameters

The wizard page for this method shows the same parameters as Markers + horizons:

• Max Depth — lower bound of the cube (default 4000 m).
• Depth Step — vertical sampling (default 10 m).
• Bottom Velocity — extrapolation velocity below the deepest tie (default 5000 m/s).

The bin grid on which the cube is sampled is chosen when the model is run, not on the wizard page (see the workflow below).

Workflow

1. Select Grid velocity by markers + horizons in the Setting up the velocity model wizard.
2. Set Datum, Max Depth, Depth Step and Bottom Velocity.
3. Populate the marker-to-horizon tie table.
4. Run the model. g-Space asks whether to build the velocity cube on an external bin grid: choose an existing bin-grid item file, or let g-Space create a bin grid, and the velocities are then sampled onto that grid.

Output

Interval and average velocity cubes sampled on the chosen bin grid, plus depth and time maps. The lateral node spacing follows the bin grid selected when the model was run.

When to use

• When downstream tools (3D-grid creation, reservoir modelling) require a regular, bin-aligned velocity cube.
• When the velocity cube must align with a specific bin grid rather than the native horizon trace grid.

For models tied to the native horizon trace grid, use Markers + horizons instead.

See Also

• Setting up the velocity model
• Markers + horizons
• Checkshot + markers + horizons
• 3D grid creating