Thread: How to interpret ASCII SAC files

Hi Shahar-

I'm not sure if you have received a response, but I'll try to answer your questions below:

This webpage still doesn't clearly explains why there are 5 columns of data.
Is it because the header is presented in 5 columns?

I believe that is what was intended. Maintaining a regular record pattern makes it easier to break down the word counts to a single array as needed. Unlike the binary format, the intent of the ASCII format is to be at least somewhat human-readable.

The webpage says the data is in 5G15.7 format. However, a Google search for "5G15.7 format" only brings me to the SAC webpage, which doesn't explain what is 5G15.7.

This is old-school FORTRAN numeric formatting. 'G' represents floating point numeric, but uses the size numbers 15 and 7 to mean the number of digits width of the displayed value and the maximum number of significant digits displayed, respectively. This URL helps to explain:

http://www.physics.nyu.edu/grierlab/idl_html_help/files17.html

The 5 before it means this is repeated 5 times.

Is the amplitudes sorted as: col1,...col5? i.e., in order to get a single column, ordered, time series, I just need to concatenate the columns vertically by their order?

They are sorted along the rows: row1,col1 ; row1,col2 ; row1, col3 ; row1, col4 ; row1, col5 ; row2, col1, row2, col2 ....etc.


-Rob

On Tue, Sep 22, 2015 at 10:35 AM, Arthur Snoke <snoke<at>vt.edu <snoke<at>vt.edu>> wrote:
http://ds.iris.edu/files/sac-manual/manual/file_format.html contains a complete description of the header in alpha format including an example.

On Sep 22, 2015, at 1:20 PM, Shahar Barak <shaharb<at>stanford.edu <shaharb<at>stanford.edu>> wrote:

Hi,

I couldn't find in the Users Manual how to parse SAC ASCII files (write alpha).
I see 30 header lines and 3 tail lines. In between I see 5 columns.
Can anyone help me or point me to the right page in the manual?

Thanks,

Shahar

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