PCX-file is being loaded into the computer memory and mapped onto a canvas. This image is viewed by the User.
Canvas view with a scanned image
The User performs time binding of the image to epoch time and sets the time scale. Then he sequentially selects, digitizes and puts out every channel as a file.
All User's commands and interaction take place directly within the graphical display windows. Control buttons appear at the top of the window.
The selection of one channel trace is performed on the basis of User's drawn horizontal axis and automatic segment cluster analysis and pattern recognition methods. The segment is an uninterrupted domain of black pixels reflected on the screen.
Automatic segment cluster analysis method
The digitization is based upon the spline approximation method. Spikes removal and Butterworth frequency band filtering may be applied optionally to the digitized traces.
Digitization of the selected segments
During the digitization process the User is able to correct interactively the list of selected segments in order to achieve a maximum of coincidence of the digitized line with channel trace. Also he may currently erase the dirt spots or other unnecessary lines, which prevent to digitizing.
Every User's step may be displayed onto a screen, thus the whole process is performed recursively.
The last stage of the trace digitization is the manual delicate editing of line by means of a mouse (if it is needed).
The digitized line (set of selected black pixel segments) is automatically cleared (optionally) from the screen that is significantly improved the further visual recognizing of the rest complex kind of "spaghetty" traces by the user.
The separate button "Enhancing" is used to rectify canvas from the vertical grid lines, which are frequently present on the datagrams and seriously disarticulate the image.
In order to avoid the "trend" effect while the filtering a special rotate procedure is used. It should be applied once at the beginning of job.
If the paper datagram is produced with the arched pen recorder, it should be previously transformed to the rectangular form with a special means (see below).
A user has a possibility to save current image (partially cleared) into a disk PCX-file at any appropriate moment of the job. This file may be then read and processed by ordinary way as a new one.
Data conversion to CSS format requires resembling and scaling of the digitized pixels coordinates values array in accordance with real data acquisition system, from which the data was received.
This conversion is controlled by the User by means of setting up new sampling rate and scale coefficient.
During resembling the new amplitude values are estimated by means of linear interpolation of two nearest pixel's values. The quality of resembling may be checked visually by drawing new curve along the old trace.
Comparison of the curves before and after resampling
The output data representation (double precision, float, integer 4, integer 2 or arbitrary ASCII format) may be selected by the User.
Generated output data is being placed into two files. A header of data array is being placed into .disc file in current directory. A header is a standard set of .wfdisc records, that includes Julian date, time of trace, name of station, channel code and other parameters of channel. It contains also a directory name for waveform file, which is assigned as a subdirectory of the current one.
If the time is the same as in present record, a new record will replace the old one in .wfdisc file and new trace will do so. Otherwise new .wfdisc file will be formed.