Thread: a problem while downsampling sac data with decimate

Started: 2010-05-25 22:01:31
Last activity: 2010-05-25 22:01:31
Topics: SAC Help
Hi All

When I tried to downsample a sac data using decimate command,I encountered a
curious problem on the delta change.
Suppose we have one data with samplng rate 100hz, and we want to downsample
to 1hz.
the cmd I used is
decimate 5, now delta=0.05;
decimate 5 now=delta=0.25
decimate 2 now delta=0.5
decimate 2 now delta=0.999999

in the final step the delta is 0.999999 instead of 1.0. Since our later
processing need to check the consistent of and we have some
LHZ sac with delta=1.0, we need to make the downsampled-data's delta to be
1.0 ,not 0.9999999.

Is there any way to aviod the 0.99999 thing ? Or we can forcely change delta
to 1.0 using ch delta 1.0 without bad effects for later processing ?

And there is another question, can sac cmd " interp "be used to downsamp
origin data ? is it differ from decimate ?

thanks for all your help in advance.


04:13:30 v.f0c1234e