TomTime has several features to facilitate data entry and examination. TomTime reads the coordinates in SG2 seismograph files as Z coordinates. If each receiver borehole has constant X and Y coordinates (negligible deviation) and the receiver spacing is uniform, then the coordinates can be entered easily in TomTime. Two other features reduce the manual entry of source and receiver coordinates in deviated boreholes. First, a source-coordinate file allows the user to assign to each source and receiver position an identifying integer, for example 155 for one source position and 145 for one receiver position. A coordinate file lists each source and receiver position once, giving the identifier and the corresponding coordinates. The source and first receiver in each seismograph
waveform file can be designated by identifiers, separated by underscores, added to the waveform file name (e.g. WEST0001_155_145.dat). TomTime can read the coordinate file before reading waveform files, and assign coordinates corresponding to the identifiers. Second, TomTime can read deviation surveys and calculate the X, Y, and Z coordinates from the distance along the borehole.
ASCII files of the waveforms can be written and read, which allows processing with a spreadsheet or other programs that can read ASCII files. It also allows regrouping of the channels. For example, suppose triaxial geophones are used, and each seismograph file contains the waveform from the vertical and horizontal hydrophones. One could form sets of data containing waveforms from only the vertical geophone by writing ASCII files of the data, then combining the desired channels with a spreadsheet.
Times from a 3dd data file from GeoTomCG can be displayed on the waveforms. This feature allows the user to compare the time-picks used for a prior tomographic inversion with the traces. Because GeoTomCG can provide a 3dd file of calculated times, this option also allows the user to display on the waveforms the forward-modeling times calculated by GeoTomCG or by other programs that use a similar data format
Much of TomTime is based on the seismic refraction program SIPWin, produced by Rimrock Geophysics, Inc. It has been revised by GeoTom, LLC for tomography under an agreement with Rimrock Geophysics.
Data files from TomTime have the extension 3PK to distinguish them from SIPWin PIK files, which have a different format. One 3PK file is generated from each waveform file. The user can select which 3PK files to combine and save in a data file for GeoTomCG. Options are:
- a) *.3dd file, contains time but not data quality or amplitude;
- b) *.3dw file, contains time and data quality but not amplitude;
- c) *.tam file, contains time and first amplitude peak but not data quality;
- d) *.t3d file, contains time and all three amplitude peaks but not data quality