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[aprssig] ELB

Keith VE7GDH ve7gdh at rac.ca
Sun Nov 29 10:27:36 UTC 2009


Andrew VK4TEC wrote...

> Does anyone know the data format GPS positions are sent from these GPS
> equipped ELB's ?

A 10 second search for ELB didn't yield much info, but changing to ELB
emergency locator beacon did a bit better. Following a link to
http://en.wikipedia.org/wiki/Distress_radiobeacon

For 406 MHz beacons...

* GPS Position can be encoded into the Hex Code and can be updated
   real-time via GEOSAR
* Encoded GPS position accuracy is about 15 m (45 ft), however, the
  space in the hex message protocol for position information is limited,
  so transmitted accuracy is approximately +/- 125 metres
* Increases in accuracy are a significant improvement over analog
  beacons - from two possible positions within a 20 km radius, to 15m
  accuracy at one position; an improvement in accuracy of over 2500.

It's kind of a vague answer, but so was your question as there are many
types of "emergency locator beacons". Assuming this is what you were
looking for, a search for GEOSAR led me to www.cospas-sarsat.org.
Maybe one of the following will be useful to you...

Beacon Coding Guide
www.cospas-sarsat.org/index.php?option=com_content&view=article&id=189&Itemid=118&lang=en

406 MHz Coding Tutorial
www.cospas-sarsat.org/index.php?option=com_content&view=article&id=188&Itemid=117&lang=en

Specification For Cospas-Sarsat 406 MHz Distress Beacons
www.cospas-sarsat.org/images/stories/SystemDocs/Current/T1OCT29.09_completedocument.pdf

In the "complete document" PDF file, scroll down to pages 45 - 57.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"




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