Navionics / GPS questions.

jamonte

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I think we will just have to disagree about Garmin's ability to make emergency messages take precedence over social messages sent NOT FROM THE DEVICE, but from the folks back home hours before the SOS button was pushed. At least give me time to call Garmin for an official answer. (Jebus, these forum discussions can become time-consuming! I would much rather spend my time paddling, thank you very much, so don't expect a definitive answer for a while!!!)

Anyhow, thanks for causing me to research this a bit more as I didn't realize Garmin's InReach messaging service and the Garmin GPS units utilize two different satellite systems! Here's a quick recap from a wiki:


Does inReach™ use the same satellites for its GPS and communication capabilities?
No, the inReach™ GPS and Communications systems use different sets of satellites. The GPS component, which attaches your position coordinates to any messages you send and also enables remote tracking, relies on the Global Positioning System, inReach™ uses the Iridium satellite system to send messages.

The Iridium satellite system relies on a few satellites placed high in geosynchronous orbit. By contrast, the Globalstar satellites, all 24 of them, are in much lower orbit. Here's more info from another wiki:

Trilateration
Garmin Global Positioning System receivers work by using GPS satellites that orbit the Earth. These satellites circle the Earth twice each day and transmit signals back. There are 24 GPS satellites in orbit as of 2008. The orbits have been arranged so that there are at least four satellites visible to GPS receivers at any one time. The Garmin GPS receiver picks up the satellite signals and uses them to triangulate the user's location through a process called trilateration. If you know you are 15 miles away from satellite A, you could be anywhere in a sphere with a 15-mile radius. But if you know that you are 10 miles from satellite B, you now have a second sphere that must converge with satellite A's sphere. To further triangulate, you add a third sphere that says that you are 10 miles from satellite C. You now know that you are anywhere within that small area where those three spheres converge.

GPS Receiver
When the Garmin GPS receives the information from the satellites, it compares both the time that the signal was sent (each satellite has an atomic clock) with the time that the GPS received the signal to calculate how far away the satellite currently is. The GPS must pick up the signal from at least three satellites in order to calculate its longitude and latitude. To calculate a 3D location (altitude) the GPS must lock into the signal of a fourth satellite. Once the receiver is able to determine the user's location, it can calculate the speed that the user is traveling by constantly updating its position with the satellites and calculating how far the user has traveled in how long a time. If the user were to input a destination location, the receiver can calculate the distance to destination and time to destination based on the user's current speed. A receiver can even tell a user when sunrise and sunset will be in their current location, since receivers such as the Garmin Nuvi are programmed with a database of sunrise and sunset times.
 

JohnAbercrombie

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A lot of folks think that GPS is a two-way system; it isn't (as you explain).
So there is no limit to how many users the GPS system can support.
If you want reliable rescue (for that time when you really need a rescue- a Mayday situation) - a PLB is what you need- IMO.
 

cougarmeat

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John, It’s a messy world. Yes, a “GPS” gets signals FROM satellites and calculates your position. BUT, these days, various GPS devices also have have the ability to communicate out - either via fixed messages set up ahead of time, i.e. “I’m here and fine.” or even back and forth dialogs. Examples are the i66GPS that combines InReach communication with Garmin mapping. One model of TheSpot also had interactive messaging. So the nomenclature can be confusing.

I do agree that carrying such a device is a good habit and I should do it on hike. I don’t think anyone who was every rescued thought they’d need to use it the day they put it in their pack.

Another recommendation is to actually USE those devices that can send back “Okay” messages - especially those that have some menu/interface with a smart phone/tablet. In a crisis, you don’t want to be asking, “What was the menu or key push sequence?”. That’s why I like the Spot - until they raised their operational prices so high - just one button push - no menus or other devices needed. And, in using it to send Okay messages, you are also testing it.

But - the PLB is a more direct connection with help. And it is a one-purpose device. no battery competition with anything else. I’d steer away from those that are water activated. Sometimes I get wet “On purpose” (even if it isn’t really on purpose).
 

jamonte

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Okay, just got off the phone with Garmin Tech Support. Turns that there were major delays on the date of my emergency and that some of my messages did not even "hit there servers" until the following day!

The main problem (which I already knew) was that I was so far down into the canyon that it significantly limited the ability of the device and satellites to make a connection. Interestingly, though, she said that while emergency messages are given priority in the message queue, every time the connection was dropped and reestablished it might have caused kind of a "reset" in the transmission of messages, which exacerbated the delay. The analogy she gave was putting your phone on "airplane mode." When you finally turn airplane mode off, (and reestablish a connection) all the recent messages you received during the interim period flood in at the same time. Not quite sure whether that analogy works re: InReach, but there it is.

She said that she has never seen or heard of any delays caused by especially high levels of traffic "overloading" the satellites and the reason is that each satellite is only overhead for 20 minutes before the next satellite picks up the signal. HOWEVER, if the GEOS servers are having problems, then long delays are possible, though she was unable to find any such notification on the day of my emergency. Interestingly, the messages I sent from my device transmitted fairly quickly while the messages I received from the satellite were greatly delayed. To me, that seems to indicate there was some sort of issue going on with the servers or satellites that day, not just poor reception down in the canyon.

Finally, she said that in areas with poor coverage it actually helps to leave your inReach device on and in tracking mode. That way, your device has already established a connection when you go to send a message. (I'm not sure how that makes sense if the messaging and GPS functions each use different satellite systems, but there it is.) Another reason I did not use tracking on my InReach in the past was to save battery power, but if leaving it on (with tracking) helps it establish and maintain a connection to the satellite then I'll start doing it. Also, I discovered by looking at the "map" on my account that when you hit the SOS button, it automatically turns on the tracking mode on your device, even if you had tracking turned off. This makes sense, but I wasn't aware that's how things worked.
 

cougarmeat

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Just a note that unlike the Spot that provides unlimited tracking points, with the InReach, depending upon which payment plan you use, you can be charged a small amount (10 cents) per tracking point. With an interval of 10 minutes, that’s 60 cents and hour. If you have it on for a 6 hour day, that’s $3.60 and for a 5 day adventure, that’s $18.00. Not a lot, but not nothing.

On the other hand, you could push an “I’m okay” preset message anytime you want and that message will include your location. So it’s sort of a manual tracking, instead of automatic.

They don’t make it easy. I’m wondering, as with what happened when I cancelled my Sirus Radio subscription, when I call TheSpot to cancel my activation, will they offer it to me at half price.
 

jamonte

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That's exactly right: Currently, InReach's cheapest plan (called the "Safety" plan) does not include any tracking points, but you can still activate tracking and pay 10 cents a point, which can add up, as you note. However, preset messages ARE unlimited and one of my preset messages says, "Here is my current location while traveling today. All is well." I usually send that message during my lunch break or when I reach my destination on a side hike. Again, my goal isn't to show every little step I take in the wilderness in real time, it's to narrow the search area down in case I go missing without hitting the SOS button.
 

jamonte

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You write your preset messages when you're in your Garmin account and then they become "set" when you synch your device via the computer. You only get three different preset messages, so it really pays to think about what information you need to convey most frequently. Once you're on your trip, you just have to power up the InReach, choose which preset message to send, and hit send. That's it.

My Number 1 preset message is: I'm camping here tonight. All is well.
My Number 2 preset message is: Here is my current location while traveling today. All is well.
My Number 3 preset message keeps changing, but right now I have: I have encountered a few challenges and might be delayed, but I'm still doing fine.

Each message shows your location on a map, so the folks back home can check your progress if they choose to. However, I have found that all they really want to know is that I'm okay. Hence, the "All is well" part of the message.
 

cougarmeat

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Just as I thought - once I decided to cancel my Spot subscription, they offered it to me at $100 less.

I had planned to use both Spot and InReach for a while to compare speed/operation but I’m sure we are staying put more this summer. Of course I could experiement walking around the block - but what’s the fun in that.

With that discount, I may keep the Spot for another year for a bigger “comparison window”.
 

JohnAbercrombie

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Just as I thought - once I decided to cancel my Spot subscription, they offered it to me at $100 less.
Thanks for mentioning that!
I got the billing reminder for my SPOT in my email Inbox a few days ago. $225 USD (about $300 CAD) so it always seems a lot.
I'm not using my SPOT just now (too many cranky communities up north) so I called SPOT and whined about the cost - didn't actually threaten to cancel. Instant $75 USD discount.
Squeaky wheel gets the grease, etc etc....
:thumbsup::thumbsup:
 

cougarmeat

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I was checking on info for the new TheSpot Gen4. When the Gen3 came out, they admitted that it had the same electronics as the Gen2. It had a longer battery life because it had … more batteries (what a concept!).

I didn’t find out anything about an improved GPS/Signal features but the do have a new pricing schedule. It looks very similar to InReach. A one time activation fee. A yearly subscription fee, and a monthly fee for the months you use it. If I understand the number correctly (have a message off to them for confirmation), as with InReach, that first month is $35, then $15/month. That’s $20 for the yearly fee and $15 for the first month of use. There doesn’t seem to be any penalty for skipping months. The Activation fee (for the device) is $25. As my Gen3 is already activated, I’d just have to pay the yearly fee and at least one monthly fee.

So I may keep it for another year to compare with InReach or perhaps keep both TheSport and InReach SE so a paddling partner would have her own signaling device instead of having to fish mine out - should I be unable to.
 
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