Thread: Amplitude error in header

My guess is that you are concerned about precision, round-off, etc.  But there
is another possible consideration:sample rate.

To see what I mean, look at
http://ds.iris.edu/files/sac-manual/manual/saclib.html#interpolation-using-cubic-splines

The second paragraph in Interpolation using cubic splines starts with "With
digital data, the extrema may not be at digitized points, ", and the figure at
the end of the section shows that just using the digital points can give results
off by several percent.

On 2/13/22 6:24 PM, Guilherme de Melo (via IRIS) wrote:

Dears,

I am applying the maximum wave amplitude for a specific time window, using the
values informed in ymax and ymin in header of the data.

So, I would like to know how much accurate is the value informed in "sh"
header command? I mean, how much percent can I consider an error of measurement?

Best,
Guilherme de Melo

Dear All -

DEPMIN and DEPMAX are the file header variables that give the extremal values of the time series. SAC refreshes these whenever a file is read in (or changed by the result of a SAC command). On disk, the data might be manipulated by an auxiliary program and the extremal values in the time series might change, but DEPMAX and DEPMAN might not be updated. That is one reason for a divergence between values on disk and in memory.

Another reason might be that DEPMIN and DEPMAX apply to the whole file. By using MTW or CUT, you can select a subset of the time series on disk and, when SAC applies those limits, it might change the values of DEPMIN and DEPMAX.

On 13 Feb 2022, at 23:24, Guilherme de Melo (via IRIS) <sac-help-bounce<at>lists.ds.iris.edu> wrote:


Dears,

I am applying the maximum wave amplitude for a specific time window, using the values informed in ymax and ymin in header of the data.

So, I would like to know how much accurate is the value informed in "sh" header command? I mean, how much percent can I consider an error of measurement?

Best,
Guilherme de Melo

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