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Summary

This document describes how to perform standard threshold target picking using the Blakely Peak Detector Algorithm (Blakely, 1986).

Pre-requisites

  1. Import surveys.
  2. Complete the production processing steps.

Target picking

Configure the picking function

  1. Starting from the Pick & Invert tab.
  2. Open the Drag & Drop Functions menu button, f(x).
  3. From the Target Pick node, drag the Detect Targ function into the target picking flow.
  4. Select the New button to configure a target picker.
  5. Following the video below enter each piece of information.
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Configuring the Blakely peak detector.

Create a noise polygon

BTField requires that the user creates a noise polygon before running a target picker. The user will be warned if the picking threshold is too close to the noise estimated from the noise polygon. Follow the steps in the video to create a noise polygon. Complete the polygon by pressing the return key.

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Creating a noise polygon.

The user may also want to record the value of the noise within the noise polygon. This can be done by right-clicking on the polygon and selecting Copy Noise Values.

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Copying noise values to the clipboard.

Run the picking function

Start the target picker by pressing the Auto-pick button. BTField may take a while to respond for datasets where many targets are found. Please wait till it’s finished. Note: the video below has had time clipped away while waiting for the taret picker to complete processing.

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Running the target picker.

Parameter definitions

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Target pickingn parameters.
  • Cfg: This shows the name of the configured picker. Each time you press New and save a new picker, it’s name will appear in this dropbox.
  • Name: User may enter or edit the name of a configured picking function.
  • ln: Select the data state to pick on. This is typically selected to be data state -a.
  • Worst case threshold from Detection Modeller: This is the threshold at which to pick targets.
  • Cell Radius: Search radius for any point that is a maximum within a circle of radius is selected as a pre-merge target.
  • Grid Sep X: Grid spacing in the x-direction.
  • Grid Sep Y: Grid spacing in the y-direction.
  • Blanking: Distance of a grid node from a data point at which to assign a null value to the grid.
  • Merge Dist: Minimum distance allowed for neighboring picks. Picks within this distance of a pick with greater amplitude will be removed.
  • Positive peaks: Toggle to allow picking of both negative and positive peaks.
  • for off-time: The time channel at which the threshold will be applied.
  • SUM: For advanced configuration of summed and specialized target picking channels.
  • Tx Cmp: Tx component to use.
  • Rx Cmp: Rx component to use.
  • Set Tx-Rx pairs: Allows user to select which Tx-Rx pairs will be used for target picking.

References

Blakely, R. J., and Simpson, R.W., 1986, Locating edges of source bodies from magnetic or gravity anomalies: Geophysics, v. 51, p. 1494-1498.

Tags: getting_started