OpendTect User Documentation version 4.2
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4.5. PickSet/Polygon

The Pickset is point data that can in OpendTect be used for several purposes, as simple point, vector quantizer, as polygons, etc. The Pickset entry pop-up menu has four options as shown below:



Load Pickset, Load Polygon will load existing picksets/polygons while New Pickset, New Polygon will create new ones.


Load Pickset... Load a previously created and saved pickset.

Load Polygon... Load a previously created and saved polygon.

New Pickset A pickset can be filled using the following three options :




Empty: Start picking from start.

Generate 3D...: Generate a pickset using range, polygon, table, or surface.

The Generate 2D... Generate random picks for a 2D data.

New Polygon... Use picksets to draw, e.g a polygon around a contour (especially useful in Common Contour Binning). You can also store your polygon as fault.

4.5.1. Manual/Empty Picksets

An empty pickset is added so that the locations (of object) are picked manually. The empty picksets are generally used for supervised neural network training (see the dGB plugins help documentation). An empty pickset is defined by right clicking on the Pickset element and selecting New > Empty from the pop-up sub-menu. In the Pickset Creation window, write an appropriate name and press OK to insert an empty pickset in the tree. For instance, lets define an object by using manual picks that are representative of salt. Display the corresponding data (line/slice/horizon) in the scene. To start picking, please make it active by clicking on it (If active, it will be highlighted). Within the scene, start clicking on the displayed data (line/horizon). Each click will add a pick. If the pick is wrong, it can be removed by using Ctrl key and left mouse-button click.


Adds empty picksets of the given name
An example of empty picks (blue) that will be used for supervised neural network training.

4.5.2. Generate Random Picks (3D)

Random picks are very important especially for prediction purposes or object detection. These are defined specifically for unsupervised neural network training (see dGB Plugin documentation for more details). Unsupervised waveform segmentation (UVQ*) is one of them. The window is launched from the tree element Pickset/Polygon > (right click) > New Pickset > Generate 3D.... The following window pops up.


Random (3D) pickset creation window

In this window write an appropriate name for the picks and select a distinct color. The generate location by contains several options: Range, Polygon, Table, Surface. It generates random picks within a selected range of inlines/crosslines/time, polygon, table, at a surface, or between two surfaces. Select and fill rest fields that are according to the selection in the generate locations by... option.

Optionally, a rejection filter can also be applied by selecting Remove locations. It passes each random position according to a selected filter (random, polygon, subsample, table, surface). It is useful to avoid random picks in unwanted regions e.g. by providing a polygon.

Provide the maximum number of locations to be inserted in the bottom text field. Fill an appropriate random number. Press OK to insert random picks.



* Note: UVQs are explained in Neural Network section of the plugin documentation.

4.5.3. Generate Random Picks (2D)

Random picks for the 2D data can also be used for the same purposes as that for random picks for 3D (read previous section). The pickset creation window for 2D random picks can be launched from the tree element Pickset/Polygon > (right click) > New Pickset> Generate 2D... sub menu. It will launch the following pickset creation window.



In this window fill/select the fields for name, a color, the number of (random) picks to be generated, on a specific lineset(/lines), geometry and Z-range. It may be noted that the specified random picks are generated according to the given geometry. The geometry is defined by a Z-range/ horizon(s). It depends upon the purpose/objective. For instance, if the objective is to detect facies by using random vectors (picks) on a surface, then horizon geometry shall be provided. Similarly, random picks can also be defined between two horizons on the selected lines.



4.5.4. Polygon

The new Polygon can be created by doing the following: Pickset/Polygon > right-click > New Polygon...
The window pops up as shown below:



Choose a name and color for the new polygon. An empty polygon folder is created and the user needs to pick a polygon on the chosen horizon or Z-slice.

Making polygons. Polygon picksets are activated by clicking on the element in the tree. The active polygon pickset is shown in reverse video and pick mode is automatically enabled. Left clicks in the graphics window will result in adding picks to the active polygon. The picks will be connected by a line. The last pick of the polygon can be removed from the active polygon with Ctrl-left clicks (use the Apple key on MacOS).

In the following picture we can see two examples of polygon picksets, closed polygon (deltaic facies belt), and non closed polygon (fault pickset).



4.5.5. Pop-Up Menus

Pickset/Polygon Element Pop-up Menu

This is the menu that pops-up when a user right-clicks on the main Pickset/Polygon element when at least one pickset/polygon is already loaded. It contains the following menu items.



Load Pickset... Display stored pickset(s).
Load Polygon... Display stored polygon(s).
New Pickset Adds a new pickset
New Polygon Adds a new polygon
Save changes. The pickset/polygon changes can be saved and reloaded at any time during the building process.
Display only at sections. Display picks on the displayed elements in the graphics area only. This mode enables picking in a new location without being distracted by previously picked points throughout the survey volume.
Show all picks. (Re)display all picks.
Merge Sets. When at least one pickset is opened in the tree, it is possible to merge picksets by right-clicking "pickset". A window pops up and the sets can be selected. A name for the output set should be defined. Picksets can also be merged from the Pickset Manager.
Show all items. Show the picksets from the tree-scene.
Hide all items. Hide the picksets from the tree-scene.
Remove all items. Remove the picksets from the tree-scene.

Pickset Sub-elements Pop-up Menu

If more than one pickset is loaded, the following options will be available in the tree:



Calculate Volume

In OpendTect, an estimated volume can be computed from a polygon to a given surface.
The velocity default is set to 3000 m/s. Negative thicknesses can either be discarded or taken into account.



Close polygon. During, and at the end of a picking session, picksets should be stored.

Properties: In this window the Type, Size and Color of the pick markers on the graphics area can be set. The type Arrow is also automatically used when the pick is given directional information in the Set directions option under the pickset pop-up menu.

Display only at sections: Shows picks on the displayed elements in the graphics area only. This mode allows to pick new locations without being distracted by previously picked points throughout the survey volume.

Convert to body: Convert the polygon into a body.

Set direction: Display direction, guided by the steering cube/attribute. This helps to understand the geological dips and fluid flow. It is assigned by setting a direction to each pick based on dip and azimuth information (attributes). In the pop-up window (see below), specify either a steering cube or two attributes providing the polar dip and azimuth in degrees. A velocity of 2000 m/s will be used in time survey to convert the dip from degrees to μs/m if the dip angle data is read from a stored cube instead of the dip angle attribute. Do not forget after setting the directions to save you pickset and change the display type to "Arrow".


An example of setting direction (black arrows) to a pickset.

Steering cube direction
Attributes input
Save/Save As: Either overwrite the stored input by using option Save or store as new pickset by using Save As option.

Create Body: Create a 3D body within the polygon bounded by top and bottom horizons.

Lock / Unlock: Lock the selected object. Prevents accidental removing, moving or displaying data on the object. Clicking "Unlock" enables editing again.

Remove: Remove pickset from tree. Note: removing any unsaved pickset will result in complete loss of data.

Export to Google KML: Export selected polygon to a Google KML file. When selected, the following export window is launched. Fill in the output KML parameters and write/select the output file location. Press the 'Ok' button to export the polygon in the selected location. The feature will prompt an additional conversion dialog if the conversion settings for the survey are not defined. For further information, please refer to the Survey Selection section.



Export the polygon to a KML file
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Random line   Horizon