---- Original message ----
>Date: Tue, 10 Mar 2009 15:03:04 -0700
>From: Geoffrey   
>Subject: Re: WinQuake  
>To: psn-l 

>
>Hello Master Kevin;
>
>This header is for a PSN TEXT FILE which I preferr to use.
>THE other called PSN4 which I believe is a binary file mifgr work
>differently.
>I have not yet tried the PSN4 format because text is so much easier to deal with.
>( Its all relative my dear einstein/watson)
>
>
>Heres the headers of which I speak, One is named work and the other Dont_Work
>********************************** CUT HERE********************************************
>In this one your data has also been cropped to start at the right second
>or as close as possible to that second.
>
>WORKS.TXT
>! PSN ASCII Event File Format 2.0
>Start Time: 2009/03/10 19:56:00
>Start Time Offset: 26
>Number of Samples:  65560
>SPS: 18.2058
>Time Reference Type: Oth
>Comment:[GVA] 
>A/D Converter Bits: 8
>Data Minimum: -33.8
>Data Maximum:  38.2
>Data Mean:  0
>! Sensor Information:
>Sensor Location: GVA
>Sensor Description: HS10-1
>Sensor Latitude: 33.42138
>Sensor Longitude: -111.57477
>Sensor Elevation: 507.5
>Sensor Incident: 0
>Sensor Azimuth: 0
>Sensor Orientation: Z
>Sensor Type: Velocity
>Sensor Sensitivity:  7.100e-008
>Sensor ID: HS-10
>Magnitude Correction: 0.00235574
>Component Name: SPZ
>Network Affiliation: IRSS
>Pick Information:
>Pick Information:
>Data:
>
>***************************************CUT HERE***************************************
>          DONT WORK
>In this one your data starts at the exact time you are trying to tell
>winquake to use.
>
>! PSN ASCII Event File Format 2.0
>Start Time: 2009/03/10 19:56:25.250000000
>Start Time Offset: 0.000
>Number of Samples:  65560
>SPS: 18.2058
>Time Reference Type: Oth
>Comment:[GVA] 
>A/D Converter Bits: 8
>Data Minimum: -33.8
>Data Maximum:  38.2
>Data Mean:  0
>! Sensor Information:
>Sensor Location: GVA
>Sensor Description: HS10-1
>Sensor Latitude: 33.42138
>Sensor Longitude: -111.57477
>Sensor Elevation: 507.5
>Sensor Incident: 0
>Sensor Azimuth: 0
>Sensor Orientation: Z
>Sensor Type: Velocity
>Sensor Sensitivity:  7.100e-008
>Sensor ID: HS-10
>Magnitude Correction: 0.00235574
>Component Name: SPZ
>Network Affiliation: IRSS
>Pick Information:
>Pick Information:
>Data:

OK. I think the issue is about what is valid in a "PSN ASCII Event File". None of the (admittedly few) examples a quick Google search has thrown up have got more than 1 decimal place in the "Start time" seconds, so it may well be that you're not allowed more than one. Is there actually a definitive spec for the file format online?

Also I can't find any reference to "Start time offset" at all, so there's no indication of what the units are.

If you can't get the file to start at a fractional second, can you not add a sufficient number of zero samples at the start?

Perhaps what's going on is that the data collection is "locked" to the 1 Hz "tick" of the external time source, so that the first sample is taken on the tick. If the data is collected over a period of a whole number of seconds, there is no need to compute partial seconds. And as long as the sample rate is not subject to a systematic drift, the actual rate can be calculated by dividing the total number of sample by the number of seconds.

Kevin
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