[OpendTect_Users] What is exactly ASCII Format of Seismic Data
bert at opendtect.org
Mon Jul 26 09:12:40 CEST 2010
> Please inform me how to define the ASCII file for in put in OpenDtect.
> What is the formated data for trace number and Posisition and what is
> for Data content.
In such situations, it may be a good idea to try to *export* a bit of
data, and see what that looks like.
The 'Simple file' format is really *simple*. The basic principle is that
every line has to contain one single trace. As always in OpendTect, the
format is completely irrelevant (tabs or spaces, number format).
Therefore I think you must have made some other mistake (like filling in
the wrong number of samples, unreasonable trace numbers, ...).
The simplest form is just a 'matrix' of data, with the trace sample
values in the rows. Like these 6-sample traces:
110.2 80 30 -0.3 -43.675 -45
102 78.3 25.4 -3 -46 -24
All the other options are 'decoration'. Thus, if your input data
contains trace number and coordinate, the file you offer to OpendTect
could look like this:
101 234567.8 3456789 110.2 80 30 -0.3 -43.675 -45
102 234569 3456803.2 102 78.3 25.4 -3 -46 -24
You can start the file with a file header, like, for example:
28 4 6
This signifies that data starts at 28 ms, the sample interval is 4 ms
(or 28 and 4m in case of depth data), and there are 6 samples per trace.
Last note: if you generate the data yourself, like in matlab, the
'Binary' option may be a good idea. For binary, the rules are:
* No whitespace at all, just binary data
* Write only local 4-byte float's and int's. Trace number,
inline/crossline and nr of samples are int's, other values are float's.
I'd always try some ascii imports/exports first, that's much easier to QC.
-- Bert Bril / OpendTect developer at dGB
-- mailto:Bert.Bril at opendtect.org , http://opendtect.org
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