PSN-L Email List Message

Subject: Re: WinQuake
From: Larry Cochrane lcochrane@..............
Date: Thu, 12 Mar 2009 00:48:15 -0700


Kevin Brunt wrote:

  > I don't run WinQuake (nor indeed a seismic sensor at the moment) but it looks
> to me as if WinQuake wants to display the data starting at a round second. (It 
> makes the divisions on the time axis regular.) I think that if you tell it to 
> start in the middle of a second, it will wind back to the sample that was taken 
> closest to the "start" of the second, and start displaying from there. This is 
> not the same as what you are describing, which is why I'm asking about your 
> data input.

Kevin has it right. WinQuake rounds to the next top of the second and starts to 
display the data from there. When you crop an event file and then save the file the 
new file will start at the top of the second.

Regarding the PSN Text Format Geoff is using. The fields are the same as the binary 
version ( just converted to ASCII. So the 
"Start Time Offset" has the following definition:

"Offset in seconds between the Start Time above and the first sample point. Start 
time = Start Time + Offset"

This field normally should be zero but can be used to add or subtract a small amount 
of time to/from the "Start Time" field.

Geoff, the following is not correct in your event file:

! PSN ASCII Event File Format 2.0
Start Time: 2009/03/10 19:56:00
Start Time Offset: 26

What you are doing is adding 26 seconds to the start. You should use 2009/03/10 
19:56:26 in the Start Time field.

 From your other event file:
! PSN ASCII Event File Format 2.0
Start Time: 2009/03/10 19:56:25.250000000
Start Time Offset: 0.000

This is correct. Since there is a fraction in the start time WinQuake will display 
the data starting at 19:56:26.

Larry Cochrane
Redwood City, PSN


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