High Sierra Topix

longri wrote: ↑Sat Mar 09, 2019 7:35 am The analysis doesn't include the up front cost of the device.

That's why I said it's a comparison of the plans, not the devices

maiathebee wrote: ↑Sat Mar 09, 2019 12:00 pmThat's why I said it's a comparison of the plans, not the devices

Yes, of course. And you were hoping out loud that someone might just buy you one. :-)

It really depends on your wants and needs. If you don't use it all year, then the freedom plan is best so you can put the coverage to sleep when not using it. If you use it all year long, then the annual plan. Still have to pay the annual, but that's not expensive.

I went with the fewest text messages, well, because when out there, I don't need or want to be in constant contact. I will text my wife if I'm running late, but only if I am running late.

I only got my device for emergencies, mine or others I might meet on the trail.

longri wrote: ↑Sat Mar 09, 2019 12:06 pm

maiathebee wrote: ↑Sat Mar 09, 2019 12:00 pmThat's why I said it's a comparison of the plans, not the devices

Yes, of course. And you were hoping out loud that someone might just buy you one. :-)

Yep. The up front cost is nothing to sneeze at for sure. You offering? ;P

I am NOT a communications engineer, but did spend my career doing satellite design (structures & systems integration). In comparing SPOT vs Garmin InReach:
SPOT uses the GLONASS (Russian) satellite constellation for tracking and the GlobalStar constellation for (1-way) messaging. InReach uses GPS satellites for tracking and Iridium satellites for 2-way messaging. GLONASS has fewer satellites than the GPS constellation, at higher-inclination orbits (more coverage at higher latitudes ... advantageous for Alaska; not so much for California). For messenging on SPOT, you need clear sky view to a Globalstar satellite that also has simultaneous view to one of their seven North American-based “gateways” (i. e. ground stations) ... no communication “sat to sat” on Globalstar. For InReach, messages received by an in-view Iridium satellite are passed on to a ground station ... or to ANOTHER Iridium satellite (and subsequently to a ground station). To an extent I’m not able to quantify, I believe this ups the odds of your SOS being sucessfully received by the InReach dispatch system.

Apologies for “burying the lead” ... just look at my last two sentences (in my previous post) in response to “Almost There”s statement

“- just saw another instance of not one but two SPOT devices failing on the same trip to trigger an SOS”
... my point being that the somewhat less robust SPOT sytem architecture (imo) likely accounts for these occurrences.

Grampy, I think that the situation is even more complicated. GLONASS uses one set of Russian satellites ("birds"). GPS uses one set of U.S. birds. Once the device figures out its location from the new of the sky, then it can send a message using the location, but that goes to yet another set of satellites. Two-way texting uses another set of satellites. SOS goes to a different one. So, each set of satellites is at a different altitude, and some are moving across the sky and some are not, so the view of the sky and what happens is a totally changing thing. There must be a dozen technical reasons why GPS can't be received and another dozen why a satellite message does not get through. Then there are other reasons why a message can fail to go through the terrestrial networks. Once you understand all of the bells and whistles, you can begin to orient your unit to maximize your chances of success for downlink, uplink, GPS, etc. Then once you get used to maximizing your chances, it becomes more or less automatic in your brain.

@bobby49 or anyone else:

Do you understand how the 2-way messaging works with the newer Spot X device? If it's the same satellite network why is the geographical coverage smaller than for 1-way messaging?

maiathebee wrote: ↑Fri Mar 08, 2019 1:31 pm Cool, thanks everyone for the input! Some things to think about re: battery life vs # of texts. hrmm hrmm

Lots of good info here, even some more financial comparisons...

https://www.outdoorgearlab.com/topics/c ... tor-beacon

I can't give you a complete answer, since I don't use any Spot devices. Geographical coverage depends on (1) which satellite system is in use, (2) the altitude of that satellite system, (3) the power transmitted from the device up to the bird, and (4) the power transmitted down from the bird. That gets into all sorts of messy technicalities. The digital length of the message dictates how long the link has to stay good to get a confirmed signal transfer, and for the birds in low earth orbit the overhead time is only 30-60 seconds for each pass. Geosynchronous satellites are all in high earth orbit, appearing to hover in one spot in the sky, so coverage tends to stay more constant, but those aren't generally used for messaging. Also, some devices use only the satellite signals that are above a certain mask angle above the horizon, since low angle satellite signals get unreliable. Believe me, we've only scratched the technical surface of this stuff, and I used to teach GPS classes.