Apply filter to the whole helicorder plot, not just zoom

[osopsa]

Tom:

From our previous conversation,

Raspberry Shake user: "It seems like I caught my first real seismic event with my Shake last night at 04:49 UTC (also registered by a professional seismic network nearby).

This event stands out a lot against my rather noisy background because its power spectral density peaks at ca 0.5 Hz, while the background noise has mostly higher frequency content.

Now, wouldn't it be useful if the helicorder display of an entire day would optionally show filtered data already, eliminating much of the cultural noise? I know how to enable filtering in the "zoom" wave window of SWARM when selecting a small segment in the helicorder display, but you cannot filter the entire helicorder display, or can you??"

Your response, "Swarm builds helicorders from data that has been downsampled in advance. This makes it very fast to present a helicorder, but also makes it difficult to filter the data.

It's an interesting idea and there are a couple of ways that Swarm and winston could get past this. Perhaps swarm could send the filter parameters to winston with the heli request? Or maybe it could work off of the full data if the user chooses to accept slower response in exchange for filtering."

I would prefer the later method, to accept a slower response in exchange for filtering. I prefer this because in the Raspberry Shake project we use the OSOP Wave Server and not Winston and OWS was not designed to receive filter requests from external applications. That kind of functionality is beyond the scope of OWS, which is strictly a wave server.

This is a low priority feature addition but would be cool to have.

Thank you for maintaining Swarm. We love it.

Branden

[osop-raspishake]

Hi Tom and friends.

I was recently at a workshop in England and a RS user expressed interest in the ability to filter the entire helicorder plot.

What possibilities are there to implement such a feature.

I concur that this would be a real nice enhancement!

branden

[rumachan]

Could I ask the developers to think about this issue again? I understand the issue with not really being able to filter data from a Winston wave server, but Swarm now supports three server types in addition to Winston. We only run Swarm off a FDSN server. In an operational situation where a volcano observatory wants to scan for LP events, for example, then filtering a helicorder, especially if using a BB sensor, is pretty essential.
Thanks,

Steven Sherburn

[dlnorgaard]

This is a popular feature request but is a difficult one to implement. For starters, as mentioned, this is not possible with Winston. For other data sources, from what I can tell given the current design, the data would have to be filtered when it is initially obtained, prior to caching as helicorder. This is not ideal since one would not be able to switch from filtered to unfiltered in the view. There is also the potential for performance issues in attempting to filter upon ingesting of data.

Although this may not help all folks, one option is to filter the data at the source to create a second channel (and rename BHZ to EHZ, for example). This is what is being done at some of the US volcano observatories. The filtering is done in Earthworm prior to import into Winston. The filtered and unfiltered channels are then both available in Swarm for viewing.

It's possible we may revisit this when we have more resources to devote to Swarm, but for the time being, it is not likely to be implemented in near future.

[rumachan]

Thanks for the explanation.