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  1. #61
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    Quote Originally Posted by DuneElliot View Post
    What a ridiculous argument above me

    It takes my InReach 2 minutes to find me and send a pre-set check-in message from the time I turn it on in the evening or morning, push the send button, to the time I turn it off, 5 minutes later...no issue with accuracy at all. It has been accurate to my exact location...every...single...time. I only use it for check-ins morning and evening; if I miss two check-ins my people know my route and my last known location and know exactly which cavalry to call. >>


    PLBs, like the one W carries, don't use tracking either and he advocates for them over lower-powered devices (or at least he did with us in Wyoming).

    Buy what you want, for what you need for YOU and your family.
    That's almost how I use it too. Except I don't use presets, cause I like to actually "talk" to the kids. But twice a day, to let folks know where I'm at, how the hiking was, etc...
    But -- how do you know how accurately it has your location? Are you checking it against a watch or phone or something?

  2. #62
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    Quote Originally Posted by jefals View Post
    . . . But -- how do you know how accurately it has your location? . . .
    GPS location is always a statistical confidence interval. And, one's "exact location" is relative to imperfect maps and/or GPS data sets, all of which have their own compromises in them. Most quality modern GPS hand sets show their confidence to one standard deviation. One standard deviation with an ideal data distribution predicts that about 68% of the time your location is within the range the GPS claims. Double the claimed distance the GPS claims and about 95% of the time you will be within that circle.

    So, if you GPS shows a location for you and claims 3 meter accuracy, that means that about 68% of the time your location is within a circle that is three meters in radius from the GPS's stated location. And incidentally, about 95% of the time your location will be within 6 meters of the GPS's stated location.

    For what it's worth, the most accurate that most civilian GPS devices can pinpoint your location is +/- 3 meters (+/- 9 ft). That doesn't mean that once in a while you wont get a GPS reading that is within 1 meter of accuracy. It means that any time you experience accuracy better than 3 meters it is random luck, not GPS precision. Conversely, if your GPS is reporting a particular location with 3 meter accuracy, about 32% of the time your actual location will be more than 3 meters away and 5% of the time your actual location will be more than 6 meters away.

    Then, to complicate things further, a particular location on your topographical map can easily be as much as 20 meters off of what an accurate GPS reading for that location will be because maps and GPS's are not always based on the same data sets. In one instance, during a multi-day back-country ski trip, my partner and I experienced about 75 m difference between a map and our GPS devices causing us to search for an extra hour or more one night, well after dark, for a shelter on the the side of a steep tree covered hill. The only way we were able to find the shelter was to head off course to a road bed that we couldn't miss and then ski back up hill on the road to find the shelter.

    More on topic, if the only ping your rescuers get from your emergency communicator is 100 meters off, which is totally possible in complex terrain if the GPS doesn't have multiple date points to average for accuracy, it can be shockingly difficult for rescuers to find you, especially in complex terrain and after dark. Remember those whistles we are always told to carry and likely have never used?
    I'm not lost. I'm exploring.

  3. #63
    Registered User Venchka's Avatar
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    I always have my Whistle!
    In fact I recently discovered that I have been carrying TWO!
    Don’t leave home without it!
    Wayne

  4. #64
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    Something else to consider... depending upon where you are, GPS can simply calculate a wrong position if signals get bounced around.

    The simple explanation of how GPS works is that GPS satellites constantly send out a signal indicating where it is and what time it is. Since each satellite is a different distance from your GSP receiver, the time stamps on these signals will be out of sync. Once the GPS has locked in on at least three satellite signals, it becomes a complex triangulation calculation of the difference in these time stamps and the locations of the satellites to determine where you are.

    But in certain locations, these satellite signals can be reflected off mountains and buildings. If the GPS manages to lock in on one of these reflected signals, it will effectively be receiving the wrong information and therefore calculate a wrong position.

    I was once near the bottom of Eagle Creek in GSMNP. The trail has some pretty steep hill sides. I knew exactly where I was, but for about 15 minutes, my GPS was telling me I was at a position that was a quarter to a half mile away while claiming an accuracy of better than 50'.
    Last edited by HooKooDooKu; 08-30-2018 at 09:07.

  5. #65
    Registered User MikekiM's Avatar
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    ????

    I'm Lost. should I hit the SOS now?

    Quote Originally Posted by DuneElliot View Post
    What a ridiculous argument above me....
    Quote Originally Posted by jefals View Post
    1234567890
    _______________________________________
    The difficulty of finding any given trail marker is directly proportional to the importance of the consequences of failing to find it.

  6. #66
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    Quote Originally Posted by MikekiM View Post
    ????

    I'm Lost. should I hit the SOS now?
    Not if you're in Baxter SP!

    But I'm now lusting after the Mini. Can't use that Explorer's damned rocker switch anyway for a real message, so might as well carry a lighter unit.

  7. #67

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    At least one has the comfort of knowing people in this forum will say they died doing what they loved when modern technology doesn't bring the calvary.

  8. #68

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    Person i hiked 200 mi with recently had one
    Worked fine for contacting wife and her tracking us
    Last edited by MuddyWaters; 08-30-2018 at 10:34.

  9. #69

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    Quote Originally Posted by jefals View Post
    That's almost how I use it too. Except I don't use presets, cause I like to actually "talk" to the kids. But twice a day, to let folks know where I'm at, how the hiking was, etc...
    But -- how do you know how accurately it has your location? Are you checking it against a watch or phone or something?
    I also send the check-in messages to myself that I look at when I get home. And my mapshare/Garmin account shows every location I've sent a message from. All the locations are within feet, if not directly on top, where I had my tent pictched aka where I send my messages from.

  10. #70
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    Quote Originally Posted by HooKooDooKu View Post
    I was once near the bottom of Eagle Creek in GSMNP. The trail has some pretty steep hill sides. I knew exactly where I was, but for about 15 minutes, my GPS was telling me I was at a position that was a quarter to a half mile away while claiming an accuracy of better than 50'.
    Here's what I don't get: it tells me my lat/long coordinates, right? I have no idea what my actual lat/long is at any moment. How do you know if it's right or wrong?

  11. #71
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    Default New Garmin InReach Mini Satellite Communicator

    nevermind, if you're looking at the flag on the map you get when you send a message. I can see on those that - at least from what I can remember from my last trip - were very accurate. (Didn’t really pay attention to them at the time)...

  12. #72
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    Quote Originally Posted by jefals View Post
    Here's what I don't get: it tells me my lat/long coordinates, right? I have no idea what my actual lat/long is at any moment. How do you know if it's right or wrong?
    Use the base map and compare to paper map, and change location format to UTM or USNG so you have about half a chance in hell of actually coming up with a meaningful number. Lat/Long is practically useless for finding position on a paper map.

  13. #73
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    Quote Originally Posted by jefals View Post
    Here's what I don't get: it tells me my lat/long coordinates, right? I have no idea what my actual lat/long is at any moment. How do you know if it's right or wrong?
    I had downloaded a set of way points for the trail I was taking, so when I reached a trail intersection or a major water crossing, I knew what way point I should have been at, but the GPS was claiming I was no where near that way point.

  14. #74
    Registered User lonehiker's Avatar
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    I was reading in another forum (Bigbendchat.com) once about someone that thought his/her GPS wasn't accurate as they couldn't find springs. The problem is that some maps (all?) of BBNP are NAD27 and not WGS84. You change your settings on your GPS and miracles happen. I, having a military background, also think that UTM is much easier than Lat/Long. But, it is what you are used to. The problem is that most people really don't understand or know how to read coordinates on a map. So without a basemap on their GPS, or a GPS track/route, they are fundamentally lost. Personally I was hoping for good discussion about this products capabilities as I ran into a situation on a recent trip that having the ability to get a message to my wife would have been useful. Instead all I have been reading is crap about how inaccurate GPS units are and that REI should somehow solve the worlds problems...

    I hope that at some point a long distance hiker, that has actually used the unit in the field, will chime in and give a good assessment of the units capabilities etc.
    Lonehiker (MRT '22)

  15. #75

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    Quote Originally Posted by lonehiker View Post
    I was reading in another forum (Bigbendchat.com) once about someone that thought his/her GPS wasn't accurate as they couldn't find springs. The problem is that some maps (all?) of BBNP are NAD27 and not WGS84. You change your settings on your GPS and miracles happen. I, having a military background, also think that UTM is much easier than Lat/Long. But, it is what you are used to. The problem is that most people really don't understand or know how to read coordinates on a map. So without a basemap on their GPS, or a GPS track/route, they are fundamentally lost. Personally I was hoping for good discussion about this products capabilities as I ran into a situation on a recent trip that having the ability to get a message to my wife would have been useful. Instead all I have been reading is crap about how inaccurate GPS units are and that REI should somehow solve the worlds problems...

    I hope that at some point a long distance hiker, that has actually used the unit in the field, will chime in and give a good assessment of the units capabilities etc.
    Bowwow has one and maybe he can chime in about what he likes and dislikes about it. He used it on this last trip to the WRR. I'd say that other than requiring a phone as the UI for messaging it was a great little unit. I liked it but prefer my standalone unit for a few reasons.

  16. #76
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    Quote Originally Posted by HooKooDooKu View Post
    Quote Originally Posted by jefals View Post
    Here's what I don't get: it tells me my lat/long coordinates, right? I have no idea what my actual lat/long is at any moment. How do you know if it's right or wrong?
    I had downloaded a set of way points for the trail I was taking, so when I reached a trail intersection or a major water crossing, I knew what way point I should have been at, but the GPS was claiming I was no where near that way point.
    Good idea. As to your earlier post re. reflecting sat. signals, seems like these would be all over the place where most of us go hiking, so seems like it would be a big problem. Wonder if there's technology to try and filter out these errant signals...

  17. #77
    Registered User Venchka's Avatar
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    Quote Originally Posted by lonehiker View Post
    I was reading in another forum (Bigbendchat.com) once about someone that thought his/her GPS wasn't accurate as they couldn't find springs. The problem is that some maps (all?) of BBNP are NAD27 and not WGS84. You change your settings on your GPS and miracles happen. I, having a military background, also think that UTM is much easier than Lat/Long. But, it is what you are used to. The problem is that most people really don't understand or know how to read coordinates on a map. So without a basemap on their GPS, or a GPS track/route, they are fundamentally lost. Personally I was hoping for good discussion about this products capabilities as I ran into a situation on a recent trip that having the ability to get a message to my wife would have been useful. Instead all I have been reading is crap about how inaccurate GPS units are and that REI should somehow solve the worlds problems...

    I hope that at some point a long distance hiker, that has actually used the unit in the field, will chime in and give a good assessment of the units capabilities etc.
    Buy the unit from REI.
    Use it for 364 days.
    Decide at that time if you want to keep it or get your money back and try something else.
    Wayne

  18. #78
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    Quote Originally Posted by jefals View Post
    Good idea. As to your earlier post re. reflecting sat. signals, seems like these would be all over the place where most of us go hiking, so seems like it would be a big problem. Wonder if there's technology to try and filter out these errant signals...
    I'm sure there's all sorts of complex things that are going on...

    Just for starters, while only three satellites are required for the basic math to work, a GPS usually can "see" 4 to 12 satellites at any given time. This allows cross checking and the ability to throw out the results from any one satellite that doesn't fit in with the others.
    I would also imagine that in most cases, a reflected signal is going to be weaker than a direct signal, and the strength of the stronger signal will suppress the weaker one.
    But in my case, being down in something of a canyon, there was likely a situation where a mountain side blocked the direct signal from a satellite, but the device managed to lock onto a "clean" reflective signal, perhaps multiple reflective signals, all positioned such that the math and perhaps even one cross check lined up and so the device reported the results.

    But this all sort of explains the basics of GPS spoofing... you can make a device think it is somewhere it is not by simulating the GPS signals strong enough to override the legitimate signals and make the device think it's anywhere you want it to be.

  19. #79
    GSMNP 900 Miler
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    Quote Originally Posted by Venchka View Post
    Buy the unit from REI.
    Use it for 364 days.
    Decide at that time if you want to keep it or get your money back and try something else.
    Wayne
    You might want to review REI's Return Policy

  20. #80
    Registered User Venchka's Avatar
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    Quote Originally Posted by HooKooDooKu View Post
    You might want to review REI's Return Policy
    What? They lied? A Gotcha clause?
    What has this world come to?
    Since I’m not in the market for a Walkie Talkie Gizmo I’ll leave the checking to those who care about such things.
    Sorry if I offered bogus advice.
    Wayne

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