SPOT should be ashamed

On Apr 30, 6:30*pm, Marc Ramsey wrote:
5Z wrote:
But there's always hope that a more pilot friendly device can be built
on top of this one by adding a few more buttons or at least changing
the firmware. *They will likely charge a bit more for the service as
we'd like to have a better chance of our live track getting received,
so it will need to send more position reports, thus cluttering the
bandwidth, etc...

I looked at implementing a SPOT-like device using this technology years
before SPOT was announced, the main problem (aside from being transmit
only) is that data messages to the Globalstar network contain only a
small number of bits (56?). *After one encodes latitude and longitude at
a useful resolution, about all that is left is a few bits to encode
"OK", "HELP", etc. *I suspect an upgrade would require more satellites,
something which Globalstar may not be able to afford...

Marc

dont you just need 1 bit to encode "okay" vs "/okay"
alright, 2 bits if you want "okay", "/okay", "fallen can't get up"

On May 1, 11:59 am, Happy Trails wrote:
On Wed, 30 Apr 2008 18:52:31 -0400, Pat Russell

wrote:
all the trouble of determining an accurate fix in three dimensions,

Is there somewhere in the specifications where it actually says this,
or are you just making an assumption here?

As far as I can tell, it can fulfill all it claims to by determining
lat & lon only. Did you mistakenly think you were buying an accurate
altimeter or something?

The GPS chipset used calculates location in 3D, like which GPS chipset
would'nt. The SPOT device does not send that over the Globalstar link
for reasons noted earlier (message length, device intended for
hikers). The specifications on GPS chipsets used in SPOT and the
Global star message formats are all public information. Lots of
information at http://www.axonn.com.

As for being ashamed, wrong! It would be great to have altitude data,
but Globalstar should be proud of their little SPOT child for leaving
home and doing well the first year away.

If people really want a 3D capable unit, designed for aviation etc.,
they are available on the Iridium network. Your imagination is only
limited by your check book.

Darryl

5Z wrote:

Except for a few bits in the message itself, there is no difference
between 911, HELP, or OK. You can test it to your heart's content by
sending either of the latter messages to yourself or friends.

I don't know about the UK, but in the US, dialing 911 from my house
just to see if it works is not permitted. So I have to trust that if
I get a dial tone, I'll be able to reach 911.

Nor do you turn on your ELT and wait for search and rescue to show up,
to see if it "works".

It's possible that the connection between the SPOT message handling
center and their 911 center is down, but I assume the message handling
system will keep trying until a human acknowledges the request. It's
also possible the 911 button on your unit is broken, but then the LED
won't flash, and you'll know it. If the LED flashes, and if a recent
OK message went out, you can be fairly confident that the 911 will go
out as well.

If you don't trust their 911 service, make the "send help" button your
personal 911, with a friend/wife/employee with email or a cell phone
ready to call search and rescue. Not as elegant, but you can "test" it.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

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