Seismic viewer for Apple Devices
How To Use
- This app is bundled with a pre-loaded SEG-Y file (the data that you first see on-screen). After you are accustomed to using the app, install Dropbox so that you can access your own data files. Make sure to use valid file extensions (.segy .sgy .seg). Capitals, lower case or any mix thereof will be accepted (.SEGY, .Seg, ...).
- Dropbox is free from the App Store. Load your seismic files here. Presently this is our data source, making Dropbox an essential companion app.
A Little Geophysics
- Wiggle: an oscillating line about a null point.
- Null point: where the field quantity is zero, as the result of two or more opposing quantities completely cancelling each other.
- Wiggle trace: a plot of seismic energy amplitude versus time from a single seismic detector. Peaks (toward right) are positive signal voltages.
Troughs are negative signal voltages. A seismic record displays side by side wiggle traces. This is the original method to display traces.
With a 'Wiggle Trace' a continuous solid line is drawn connecting each sample to the next.
- Wiggle Variable Area (VA) trace: a wiggle trace on a seismic section with the recorded energy peaks or lobes (toward the right) are filled in with black.
Essentially only samples having positive values are drawn and the area between 0 amplitude and the positive value is filled in by a solid color.
- Signal: a detectable physical quantity or impulse (as a voltage, current, or magnetic field strength) by which messages or information can be transmitted.
- Waveform: the shape of a wave, typically shown as a graph of amplitude (or other quantity of interest) versus time. Waveforms are referred to as functions of time.
- Wave: A periodic vibrational disturbance in which energy is propagated through or on the surface of a medium without translation of the material. Waves can be differentiated by their frequency, amplitude, wavelength and speed of propagation.
- Frequency: number of waveform cycles per unit time.
- Functions of distance: frequency is replaced by spatial frequency or wavenumber (number of waveform cycles per unit distance).
- SEG-Y: a file format, and a standard, from the Society of Exploration Geophysicists (SEG). Such files contain geophysical data.
- Seismic reflection profiling: an echo sounding technique, where a controlled sound pulse (sound energy) is issued into the Earth and a recording system listens a fixed time for energy 'reflected' back from interfaces within the Earth.
Features and design
- Purpose: to visualize seismic data on a handheld pocket device.
- Platforms: iPod, iPhone, iPad.
- Minimum hardware: GiOS was designed to work well on a mimimalist Apple device, right down to an iPod.
- Visual design: step through and focus on single waveforms (traces), or pan and zoom through the complete seismic section.
- Portrait mode (device upright): the screen is divided into 3 active zones.
- Zone 1: Top of screen is a single trace, the live 'focal' trace.
- Zone 2: Middle of screen is a Wiggle plot cross section. A wiggle plot contains multiple traces, plotted from left to right. Each trace starts at the surface and penetrates the ground to its maximum travel depth.
- Zone 3: Bottom of screen is the Headers Section. Mainly for metadata, describing the datasets themselves, as represented in zones 1 and 2.
- Loading: Data is acquired from Dropbox.
- GiOS copies data to it's own storage area, so is no longer dependent on Dropbox once data is acquired (downloaded). Data can thus be worked on even if Dropbox is removed, or when the device is completely off-line.
- The iPhone icon gives access to locally stored files.
- The Dropbox icon gives access to Dropbox data, by running the Dropbox app. If the file is already local, that copy will be used, otherwise the file will be downloaded.
- Deleting GiOS will wipe any of its locally stored data
- Touching a section makes it active. Turning your device into landscape mode (flipping sideways) will expand that section so that it is now fullscreen.
- Double tapping an area flips it to landscape, full screen mode
Dragging and scaling
- Dragging: depending on the zone, the screen responds to dragging left<-->right and top<-->bottom
- Pinch-zoom: standard pinch to zoom operates on the wiggle plot, in both portrait and landscape modes.
About the Author
- Alex Garrett
- Software Engineer (M.Sc. Computing Science).
- Geologist (B.Sc., Honours, Earth Science).