OpendTect dGB Plugins User Documentation version 4.2
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3.3. Create/Edit Horizons from a SteeringCube

Create Horizons

dGB provides utility features to create and manipulate seismic horizons using SteeringCube. The utilities use an ultrafast algorithm to track horizons within a seismic volume using SteeringCube. The only requirement is to have a good SteeringCube to produce full 3D horizons within few seconds or minutes, without the need for gridding or interpolation. These horizons can be used as an input to a HorizonCube. It is launched from the HorizonCube sub-menu "Create horizons from SteeringCube".

Create horizons from SteeringCube.

In order to create a horizon through using a SteeringCube, several inputs are required: a SteeringCube, faults and seeds. Select the SteeringCube by clicking the Select button next to the Input SteeringCube field. Optionally, a sub-selection of the SteeringCube volume can be selected if the intention is to create the horizon within a sub-volume.

The faults should be provided to adequately incorporate the fault throw while tracking the horizons from the selected SteeringCube. Press the Select button for the Faults field to select one or more faults from the pop-up fault selection dialog.

Advanced settings: The advanced settings for this utility are:
(a) Pre-load: The Pre-load full volume is checked to load the SteeringCube into the memory before tracking horizons. This speeds up the tracking of multiple horizons. Note that if the SteeringCube size is larger than the size of the available memory this option should be left unchecked. Alternatively, change the volume sub-selection for the SteeringCube (e.g. reduce the Z-value).

(b) Stepout: The stepout (inline : crossline) parameter controls the spatial quality of the horizon-tracking in 3D. It defines the number of z-values (of an event) to be used to forecast the z-value at a new trace position. By default the inline steps are set to 1 (i.e. 3 z-values on a crossline plane) and the crossline steps are set to 4 (i.e. 9 z-values on inline plane). Smaller stepouts equal faster and detailed dip field tracking while larger stepouts are preferable for regionally consistent events. The best practice is to test asymmetric parameters (e.g. 1:4 or 4:8 or 1:12). The symmetric steps (e.g. 4:4, 8:8 or even higher 12:12) are usefulfor averageing out very small details / noisy trails while tracking. It is strongly recommended that the optimal stepout parameter is tested through this utility prior to creating any HorizonCubes.

Apply starts processing and creates horizons. Once the horizon tracking is finished, the horizons are displayed in the scene.

In the Create horizon(s) from SteeringCube window, several icons are used to create and to save multiple horizons simultaneously.

Pick a seed to track horizon on displayed seismic data (Inline/Crossline) in the scene. For corresponding horizons (table) one seed should be picked. Optionally, if fault(s) are selected, one seed should be inserted per fault block.
Adds a new horizon in the table.
Removes the selected horizon from the table.
Saves the tracked horizon(s).
Launches the HorizonCube Creator setup (see Section 3.4 Create HorizonCube)

An example of inline on which the seeds (red, yellow, and blue) for three horizons are picked. Note that one seed is picked within a fault block. The current algorithm tracks a full horizon using one seed only and extends tracking outward within the range of the SteeringCube.

Edit Horizons

To fill holes or to re-track existing horizons using the SteeringCube, the similar utility can be launched from the HorizonCube Sub menu (Processing > HorizonCube > Edit horizons with SteeringCube. The action will pop-up the following window which is almost identical to the 'Create Horizon(s) from SteeringCube' window presented above. The SteeringCube is selected in the Input Steering Cube field. Additionally, any faults can be selected. The Edit Options are used to either fill the holes/gaps or to re-track a horizon using the SteeringCube.

Edit existing horizon(s) using the selected SteeringCube.

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Data Preparation		Create HorizonCube (2D/3D)