Array Selection and Display Settings

Select the primary array channel to display.

• Defines the primary axis behaviour for the graph.

• Plotted in blue.

This contextual parameter applies only to EM utilities.

Choose how to display error bounds around the 1st array channel:

• None: No error envelope is displayed.

• Display onboard noise: Available only when noise values are stored in the channel registry (see Define Noise).

  When selected, an error envelope is plotted around the 1st array channel, calculated as the 1st array ± stored error.

• Display 2nd channel as error: The selected 2nd array channel is interpreted as the error envelope magnitude.

  The envelope is plotted as 1st array ± 2nd array using two dashed curves.

Include error in range

If selected, the Y-axis expands to include the full error envelope.

An error envelope can only be displayed for the 1st array channel.

Select an additional coincident array to display.

• When no error envelope is selected, this channel is plotted as a green curve.

• When Display 2nd channel as error is selected, this channel is not plotted independently. Instead, its values define the upper and lower dashed error bounds around the 1st array channel.

Select an optional third coincident array channel. This channel is plotted in red.

Select the survey line to view.

You can also move between lines using the Up/Down arrow keys.

All selected channels share a common vertical scale. Choose one of the following options:

• Fit each row: Recalculates the vertical axis for each displayed row so all channels fit optimally. The scale updates automatically as you move through rows.

• User-defined range: Allows manual control of the vertical axis. When selected, the Minimum value and Maximum value fields become editable.

• Same axis for each line: Calculates a single scale per line using all channels in that line. The scale remains fixed while scrolling through rows in that line.
• Same axis for all lines: Calculates one scale that fits all selected channels across all selected lines. The scale remains constant while scrolling through both rows and lines.

By default, the Y-axis range is calculated based on the currently displayed profile (and the error envelope, if shown).

The Minimum value and Maximum value fields are automatically populated with these calculated limits.

To override the automatic scaling, select User-defined range and enter custom limits.

By default, VCA uses a linear vertical scale.

For data spanning several orders of magnitude, choose:

• Log (logarithmic): Plots values using a logarithmic scale.

• Log-linear: Dynamically switches between linear and logarithmic display depending on the magnitude of each value.

Define how the span of the vertical axis is calculated.

• Scale to first channel only: Since the first selected channel is the primary focus, the Y-axis is, by default, scaled to the range of the first channel only. This ensures it is displayed with an appropriate dynamic range regardless of the values in any additional channels.

• Scale to all channels: The Y-axis covers the range of all displayed channels combined.

This setting controls how low data values are displayed, depending on the selected data scaling mode:

• Linear: This option is not applicable and remains disabled.

• Log: Data points with a logarithm smaller than this threshold are not plotted.

• Log-linear:

If the absolute value of the logarithm of a data point exceeds the specified minimum, it is plotted on a logarithmic scale.

If the absolute value is below this minimum, it is plotted on a linear scale.

By default, profiles are displayed as a function of array element indices, using equally spaced intervals (Equal).

If the array base property for the first displayed array channel is set, the horizontal (X) axis is annotated using the units of that base property. These increments can be spaced as follows:

• Linear: Uses the actual increments with linear spacing.

• Log: Uses logarithmic spacing based on the true increments.

Axis annotations update automatically based on the selected mode.

Initially, the entire array (or arrays) is displayed. You can, however, display a subset of the data by specifying the first and last elements. These parameters are defined as array indices, regardless of whether a base property is set.

Any leading or trailing dummy elements in the array are automatically excluded from the display by default.

Array selection and display settings are retained when the dialog is closed and persist across sessions.

Graph Display and Legend

The right-hand side of the dialog contains the plot area. The graph updates dynamically whenever you:

• Change one or more selected array channels

• Modify display or scaling settings

The plot supports up to three coincident array channels, rendered in a single graph for comparison.

Visual Differentiation

Each array channel is visually distinguished using one or more of the following:

• Distinct line colours for each channel

• Symbols indicating array element positions

• Optional contextual error envelopes

The legend in the upper-right corner of the plot identifies each channel and its corresponding colour and symbol.

Error Envelopes

An error envelope can be displayed around the first array channel to visualise measurement uncertainty or variability.

• The error envelope is derived from the second selected channel, when configured as an error source.

• Optionally, the error contribution can be included in range calculations.

Example – EM Data

The following example shows electromagnetic (EM) data with an error envelope plotted around the first array channel.

Coincident Array Behaviour

The first selected array channel defines the graph behaviour including:

• The array base property (for example, energy, time, or wavelength)

• Axis interpretation and scaling logic

When additional array channels are selected, VCA assumes they share the same array base property as the first channel.

Example – Spectral Radiometric Data

The example below shows spectral radiometric data plotted using three coincident array channels.

The NASVD-smoothed channel is displayed as the third coincident array, allowing direct comparison with the raw data.

Graph Axes

• X-axis: If Array Base Properties has previously been invoked on the primary array channel and increment units have been assigned, the X‑axis is annotated using those units. In this case, the axis label reflects the assigned units (for example, ms or keV).

  Otherwise, the X‑axis is annotated using array indices and no axis label is displayed.

• Y-axis: If the array channel units have been previously set by invoking the Edit tool on the channel’s right-click context menu, the Y-axis will be labelled accordingly.
  

Array Navigation

Use the controls located below the graph to navigate through the array:

• A horizontal scrollbar allows you to scroll through arrays along the selected line.

• Arrow buttons enable navigation along the selected line.

These controls make it easier to inspect specific windows or array elements, particularly when multiple channels overlap. Array navigation control positions are retained when the dialog is closed and reopened.

Symbol Size Control

To help distinguish overlapping arrays, you can adjust the symbol size directly from the legend:

• Click the left end of the topmost legend entry to decrease symbol size.

• Click the right end of the topmost legend entry to increase symbol size.

The symbol size ranges from 0 to 4 pixels.

VCA remembers the last symbol size used and reapplies it when the tool is reopened.

Tabulated Cursor-Position Values

The numeric values at the cursor position on the graph are tabulated below the plot. The data table at the bottom of the dialog displays detailed information for the array element under the cursor, including:

• Fiducial number

• X, Y, and Z coordinates (if assigned)

• Array index

• Base property of the array channel

• Scalar values for each displayed array channel

If the VCA dialog is open while you make changes to the underlying database, click Refresh to update the graph and display the latest values.