The WaveView Window

This window allows viewing of any number of stream waveforms over a full range of zoom factors. The application can have any number of these windows open at any time. Any stream may be viewed simultaneously in many different windows, each at a different zoom factor. Controls within this window are :

• Select Amplitude scaling or Up and Down arrow keys
• Select Time scaling or Left and Right arrow keys
• Calculate Offsets for waveforms or ‘N’ key
• Pause waveform scrolling or Pause key
• Access the Print Features
• Access the Auto-Screenshot Feature
• Take measurements of time and amplitude
• Change waveform and background colours
• Switching the default or user-defined filter on and off or ‘F’ key. Ctrl-F opens the filter-design window.
• Show/Hide block markers or ‘M’ key
• Select data for external manipulation

Streams may be moved between WaveView windows by dragging and dropping. To copy a stream display to another window, hold the Control key whilst dropping. An indicator shows where the dragged stream will be inserted when dropped.

To access the options for each WaveView window, and the associated stream views, use the popup menu for the window (Right click when the mouse cursor is inside the window). To perform an operation on a stream, ensure that it is focused.

The filter option allows a bandpass filter to be applied to the stream waveforms as they are drawn. The filter can be an in-built default, or a user-designed filter.
Two different default filters are available:

• For 1 or 2 samples/sec data, a bandpass filter is selected with passband in the 10-30 second period.
• For all other sample rates, the filter has corner frequencies of 0.1 and 0.9 of the nyquist frequency of the stream. This is useful when displaying a broadband instrument, and the long period signals are preventing a ‘flat’ display.

The width of the label panel on the left of the window can be increased or decreased to suit the length of the stream labels. To change the size, point the mouse at the right-edge of the panel where the cursor changes to a left-right arrow with vertical lines (), then click-and-drag the edge left or right. The stream labels will resize to fit the available space (subject to a maximum size).

The toolbar and caption bar (in Windows) can be hidden, using the ‘No Caption’ option in the popup menu. This maximises display area for the streams. Keyboard alternatives to the buttons on the toolbar are available so that the window appearance can still be changed when the ‘No Caption’ option is selected.

There are a number of keyboard shortcuts that can be used to change the display parameters of the WaveView window. These are listed below.

The spectrogram is plotted linearly, where the top of the ‘band’ represents ½ the sample rate (the ‘Nyquist’ frequency), and the bottom of the band represents DC. For ‘temperature’ colour coding, a natural log rule is used to provide maximum sensitivity at low signal levels, whilst providing a large total range.
When a spectrogram is displayed, an extra frequency scale is drawn on the left-side of the spectrogram. It is possible to zoom in on a frequency band of interest by dragging a selection in this frequency scale. To scale all spectrograms in the window to the same frequency range, hold CTRL whilst selecting.
You can repeat the selection to zoom further and further in, and to undo a zoom (zoom out), right-click on the frequency scale (holding Ctrl if necessary to zoom out all spectrograms).

The Block Markers indicate where the data is packeted into GCF blocks, the compression level for each block, and whether the block was received realtime or whether it was "recovered" after being lost in transmission. They also show if a log of a re-boot or a re-sync to GPS has occurred, which can be useful as a quick indication why there may be a gap in the data.

See Also:

Offsets, Measurement cursors, Data Selection, MatLab interface