EARTHWORM COMPATIBILITY

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Earthworm Wave Viewer -- click for large photo

Earthworm Overview

Symmetric Research supports Earthworm under Windows and Linux. Earthworm is a public domain collection of programs for acquiring, processing, and saving earthquake data that has become popular with many geophysicists. There are versions of Earthworm running under Windows (WinNT, Win2K, WinXP), Solaris and Linux.

Earthworm is composed of many separate programs, called modules, which read and write data from shared memory regions known as rings. Some modules send data from one ring to another over the network. This allows Earthworm to run in a distributed fashion using several different computers.

PARxCH and Earthworm

Any of our PARxCH 24 bit A/D's can be used to supply acquired data to an Earthworm system by running the SrParxchEwSend module. Once Earthworm is up and running, SrParxchEwSend starts acquisition on the PARxCH and sends the acquired waveform data to the WAVE_RING specified in the usual Earthworm style .d configuration file. It also sends regular heartbeat messages.

In order to run SrParxchEwSend, you will need a working Earthworm system, a PARxCH A/D system, and the PARxCH device driver software that comes with the system and is also available free from our download page. One, four, and eight channel versions of the low cost PARxCH A/D's are available. With Earthworm, sampling rates up to 1000 Hz are allowed as long as the rest of your Earthworm processing can keep up.

If accurate timing information is important for your application, you will also want to use our PARGPS timing unit for timestamping the acquired data. The time stamping is done in the hardware and does NOT require feeding PPS into an analog channel. For the PAR1CH and PAR4CH, typical time stamp accuracy is 10us, while the PAR8CH delivers an improved accuracy of 800 ns.

Earthworm systems are well suited to distributed networks. When setting up a remote node or field station, you may want to consider pairing a PARxCH A/D with a commercially available Mini ITX System. These compact, low priced PC's are easy to use and typically have low power requirements too.

SrParxchEwSend will work for Win2k/XP and Linux since those are the operating systems for which PARxCH drivers are available. There is no support for Solaris.

General questions about Earthworm are probably best answered by the Earthworm User's discussion group. But, if you have specific questions about SrParxchEwSend and its configuration parameters, please let us know at info@symres.com.

Earthworm Links

• CERI at Univ of Memphis has the Earthworm Code and Documentation
• New Mexico Tech hosts earthw, the Earthworm user's group

Download SrParxchEwSend

The SrParxchEwSend Earthworm module is included in the standard Earthworm distribution starting with version 6.3. It is also included in the PARxCH with PARGPS system software which is available free from the PARxCH 24 bit A/D's with GPS Timing section of the download page. Of course, the PARxCH hardware itself is required if you want to acquire data with SrParxchEwSend.