INTRODUCTION
INTRODUCTION
AUTOMATED DIGITIZING
SYSTEM FOR SEISMOLOGICAL PAPER RECORDS PROCESSING is intended to digitize
photographic and other paper seismograms, and to convert this data into
standard files of CSS 2.8 format. Photo and paper records are to be scanned
previously into PCX-format files. Other output format may be added if requested.
Source information:
PCX-file of multichannel seismogram.
Results: Corresponding
.wfdisc and data files in current directory.
Supported platforms:
PCX-file is being loaded into the computer memory and mapped onto a canvas. This image is viewed by the User.
The digitization is based upon the spline approximation method. Spikes removal and Butterworth frequency band filtering may be applied optionally to the digitized traces.
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.
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.