Thread: LEVEN = TRUE but IrisFetch (Matlab) says "Data is unevenly spaced"

On May 3, 2022, at 6:13 PM, George Helffrich (via IRIS) <sac-help-bounce<at>lists.ds.iris.edu> wrote:

Dear All -

From reading the Matlab code, this is a bug that should be reported to the maintainers at IRIS.

Briefly, the code cannot handle V7 SAC files properly; if the version number is not 6, the code assumes it is just a byte-swapped SAC file. It does not recognize that V7 headers exist.

On 3 May 2022, at 20:02, Loring Schaible (via IRIS) <sac-help-bounce<at>lists.ds.iris.edu <sac-help-bounce<at>lists.ds.iris.edu>> wrote:

I converted some SAC files that were originally V6 (NVHDR = 6 ) to V7 (NVHDR = 7). I then did a transfer to produce a velocity time-series file. The original and product files are now in V7.

When I try to load either V7 sac file into Matlab, it will not load any data and returns:
Error using irisFetch/read_sac_in (line 2485)
IRISFETCH:read_sac_in - Data is unevenly spaced.

However, when I open the header of either V7 file,
LEVEN = TRUE
And the SAC manual says "LEVEN TRUE if data set is evenly spaced"

I do not have a problem loading the V6 sac files into Matlab. I do not get this error message in Matlab. But, as far as I understand, I need to have it in V7 for the sake of the accuracy of my time values.

How do I resolve this?

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George Helffrich
george<at>elsi.jp <george<at>elsi.jp>

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