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GCFInfo 1.5

GCFinfo is a Windows (all versions from 95 up) add-on for viewing, manipulating and saving Güralp Compressed Format (GCF) files. It is designed to be a seamless extension to the operating system, offering both shell extensions and drag-and-drop functionality:

  1. Display waveform data in a graphical window, allowing zoom functions for examination of the data and a user-customisable MATLAB® interface
  2. Display header information (such as sample rate, start time, etc), and the numerical sample values contained within the data
  3. Offer manipulation tools for easy management of the data files


GCFInfo v1.5 for Windows (507 K .zip)

This windows binary uses the QT runtime DLL file qtintf70.dll. This is normally installed with Scream! but, if it is not installed on your system, you will receive an error message when you try to run this software. You can download this DLL from here. It should be placed either in the same directory as the program or in the system32 directory.


You need to be logged on as a user with Administrative privileges (this does not apply to Windows 95/98 users). If you have insufficient privileges, you will get the error message 'Failed to register'.

To install GCFinfo:

  1. Unzip the files GCFinfo.exe and GCFmenu.dll to a suitable directory (e.g. C:\Program Files(x86)\Guralp Systems)

  2. Run GCFinfo. It will ask:

    Answering Yes to this will link GCFinfo into the shell extension, which adds the view, open and combine options to the context menu for files with the GCF extension. In addition, TXT files can also be combined. For details of how to use these options, see below.

    If this confirmation is not displayed, then the association already exists (normal for installing updates). To install an update, simply copy (or unzip) the files over the existing ones, replacing them.

  3. When registration has completed, close the GCFinfo window.

  4. You may wish to create a shortcut on the desktop. GCF files can be dropped onto the shortcut icon for viewing.

This associates the GCF file-name extension with GCFinfo.


Shell extensions allow applications to add functionality to the windows shell (usually seen as the windows explorer). To access these extensions from the explorer, select the files, and then either right-click on them, or use the _File menu option:

Combining two GCF files

The additions to the context menu options depends on the number and type of files that are selected. There are three possibilities:

View Window

The view window

The View window allows the user to zoom in and out of the waveform.

You can also use your mouse wheel to zoom in and out. Use the shift key to switch between Amplitude and Time scales, and the ctrl key to switch between zoom and scroll functions. The status bar on the bottom of the window indicates the active function and changes as you press or release the shift and ctrl keys.

The mouse cursor changes to a cross and its coordinates are indicated by red lines on the rulers at the left and bottom of the display, as well as being shown numerically in the menu bar. This allows precise measurements to be taken of features of the displayed waveform.

A MatLab interface allows selection of an interval of time data for transfer to a MatLab 5 or later automation server, and execution of a pre-named script. To activate this function, perform the same action as for a zoom in, but use the right-mouse button. When the button is released, a context menu will be displayed offering a menu of options for the currently selected data.

To print the current selection of data, simply select the _File → _Print menu option. This behaviour depends on whether the window is 'docked' to other windows.

Once a view window is open, it will accept drag-and-drop operations from the Windows Explorer. This operation will replace the currently viewed files.

To save the displayed waveform data to a file, select the _File → Save _As menu option. This saves the currently displayed time window to a single file with the user-specified file-name. Note that the saved file may contain a few more seconds either side of the specified time. This is due to the program working in complete GCF blocks.

For file formats that don't support discontinuous data (eg SAC), any gaps in the data sequence will be padded with the value zero.


Each View Window can only display one stream's data. The View windows can, however, be docked together to give a grouped view of multiple stream waveforms.

To open more than one View Window, repeat the shell view operation for GCF files as detailed above. To dock a window into another, simply drag it over, observing the outline marking drop position, then release when the desired arrangement is shown. By repeating this, many streams can be displayed side-by-side.

There are a number of advantages of docking windows together:

To undock a window from a dock set, simply drag it (using the double-bar handle) out of the 'set' window.

Examining GCF Details

From the 'Open' shell operation, or when run without any parameters, the details window is shown.

The text info display

This window lists all selected files, with information regarding their content, allowing the user to zoom right in to the individual sample values.

This window accepts drag-and-drop operations from the Windows Explorer to add files to the set. By selecting one or more of these files, and right-clicking, a menu is displayed for further examination of the data.

The Block Details option opens a child window which lists the details of the blocks in the selected file. Double clicking on a block opens yet another window which lists the individual differences and integrated sample values within that block.

Sample details


To uninstall GCFinfo and the shell extension, run GCFinfo with the /unregister option. e.g. If the above installation directory was used, select Start → Run and type:

"C:\Program Files(x86)\Guralp Systems\GCFinfo" /unregister

GCFinfo will then confirm that it has successfully unregistered.

The two files GCFinfo.exe and GCFmenu.dll can then safely be deleted, and the directory removed. Any created shortcuts can also be deleted.

For more information, first contact your local distributor or email .