[webservices] Requesting decimated data

[Bruce Weertman]

Hi Elizabeth:

The decimation feature of ws-timeseries is only able to decimate  to certain sample rates.

As stated in the docs:
    "The sample-rate of the source divided by the given sample-rate must be factorable by 2,3,4,7."

>> I see that this is a mistake, the 4  should be a 5 - will fix this ASAP <<

For example, if the original data is 50 sps, then you will not be able to get to 4 sps since 50 / 4 = 12.5 which is not factorable by 2,3,5,7.

However, you would be able to get to 5 sps since 50 / 5 = 5

For a BHZ channel like net=IU, sta=ANMO, loc=00, cha=BHZ the sample rate is 20 sps
So you could get to 5 sps since 20/ 5 = 4 and 4 is factorable by 2,
You could also get to 4 sps since 20/4 = 5.

In general going to 5 sps should be a safer bet than going to 4 sps.

At some point in the future we will likely have an interpolation feature to go to arbitrary sample rates, but we're not there yet.

In the near term, another point for improvement would be to have better error reporting. I'll take a look at this.

Hope that helps. 
If not, please feel free to send me a list  what you're requesting and I'll see if we have a problem on our end of things.

Cheers,
Bruce

--------------------------------------
Bruce R Weertman
Software Engineer
IRIS DMC
1408 NE 45h St, Suite 201
Seattle, WA 98105

bruce at iris.washington.edu
(206) 547-0393

On May 23, 2012, at 3:09 AM, Elizabeth Entwistle wrote:

> Hi All,
> 
> Does anyone know a way of requesting decimated broadband data, for example BHZ data decimated to 4sps? I have tried using the ws-timeseries url query by adding the "deci=4" option, but this only seems to retrieve data from a select few stations.
> 
> Any help would be much appreciated!
> 
> Many thanks and best wishes,
> Elizabeth.
> 
> -- 
> Elizabeth Entwistle
> PhD Student
> 
> School of GeoSciences
> Grant Institute
> The King's Buildings
> West Mains Road
> Edinburgh
> 
> 
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
> 
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