The Great Big SPOT Thread

Discussion in 'Mapping & Navigation' started by John E Davies, Nov 6, 2007.

  1. offroute

    offroute Been here awhile

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    The perfect use. I don't think you'll see any significant issues with the use you're describing. All my testing on the highway has been good regarding getting my Tracking locations and Check Ins out etc. A great tool to have along on any ride.
    #21
  2. TomW

    TomW Long timer

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    Yep, based on what I learned he's right about that, and so are you. I learned from my bro that their satellites are not in true polar orbits (where the satellites wouldn't favor a specific location on the earth). They're in orbits inclined at 52 degrees to the equator, meaning they won't go north of 52 degrees north latitude (or 52 degrees south latitude). Also meaning that at any given time, for those of us in the northern mid-latitudes, more satellites are likely to be south of us than north of us. Some may be overhead or north of us (as long as we're south of N52 deg), but it's slightly more likely that they'll be to the south. I don't know how significant the theoretical latitude factor is, but your informal test to date seems to bear out the generalization.

    GlobalStar is having some tech issues with their satellites and from what I gather, they're pushing data applications over voice until they get their second generation birds up starting in 2009.

    Interesting factoid my brother picked up: the competing sat phone system (Iridium) was planned for a constellation of 66 satellites and 11 orbiting spares for a total of 77 in polar orbits. The atomic number of iridium is 77.

    I think GlobalStar looked at population distribution and decided that most people lived between N52 and S52, so a smaller number of satellites (40) could satisfactorily cover that area from inclined orbits. Clever.

    Cheers.
    #22
  3. offroute

    offroute Been here awhile

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    Interesting info TowW. Thanks!

    I've used GlobalStar sat phones in central Idaho a few different times. I was constantly having to climb up different sides of the Middle Fork Salmon canyon walls to be able to use the thing. It was pretty frustrating. My experience with the SPOT device here in the Tahoe area is certainly much better than that.
    #23
  4. markgsnw

    markgsnw WTF?

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    how are we doing here? any updates?
    #24
  5. willyvee

    willyvee old timer

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    <TABLE class=tborder cellSpacing=1 cellPadding=4 width="100%" align=center border=0><TBODY><TR><TD class=thead colSpan=2></TD></TR><TR title="Post 5697914" vAlign=top><TD class=alt1 align=middle width=125>markgsnw</TD><TD class=alt2>how are we doing here? any updates?</TD></TR></TBODY></TABLE>

    While sitting here with a broken leg, I am vicarously watching my son, Offroute, having fun. I tracked him and his friends from their campsite under a tree west of Lone Pine Wednesday night, and yesterday in almost realtime do Saline Valley, Lippincott Canyon, Racetrack, Teakettle Junction, Hunter Mountain and Cerro Gordo in Google Earth Hybrid. Today, I am tracking them from their campsite at Furnace Creek, and they are presently up in Echo Canyon. This tracking feature is amazing. wv
    #25
  6. KenR

    KenR Long timer

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    I went out today for a quick 175 mile loop. Pressed the OK check-in button five times throughout the ride and everyone on my list got text messages and emails within a few minutes. I haven't tried the tracking feature yet - maybe tomorrow - but I'm very impressed.
    #26
  7. TomW

    TomW Long timer

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    How do you guys have the Spot unit mounted on your bike?

    Cheers.
    #27
  8. KenR

    KenR Long timer

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    I just throw mine in the front pocket of my enduro jacket - don't even know it's there.

    One thing that did happen yesterday has me a bit perplexed.

    I have a Garmin 276c mounted on the bike. At two different times yesterday the GPS seemed to lose it's position, presumably after I hit the OK button of the Spot. The speed was still reading correctly in the display, but the map froze up and showed me about 300 miles from my correct position. Both times I simply rebooted the GPS and it went back to working correctly.

    So I'm wondering if there's a conflict between the two devices or if this was just a coincidence. I've never had that happen with my 276 before yesterday. The Spot recorded all of my check in's correctly. This obviously calls for more testing before winter arrives here on Monday - at least that's what I'm telling my SO. :D

    Anyone else have this happen?
    #28
  9. TomW

    TomW Long timer

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    I'm not surprised. The GPS satellites transmit in a band at 1,559 - 1,610 mHz and GPS receivers need to be quite sensitive as they usually don't have much antenna to work with. The GlobalStar/Spot systems' handset transmits in the band 1,610 - 1,625 mHz with significant power necessary to access a satellite in an orbit 1,000 miles up (again with little help from the antenna). This probably overloads the GPS' receiver. I doubt that these civilian units are designed to reject relatively huge signals on adjacent frequencies.

    A cure? Dunno -- anything you can do to separate the GPS and Spot antennas as much as posible will help. Let us know if you have any luck with this.

    Cheers.
    #29
  10. DRTBYK

    DRTBYK All Things GPS

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    I would think (?) that the hardware designers accounted for the proximity of transceivers and provided the appropriate filtering. Otherwise it wouldn't work at all. But they probably have a very small antenna for the GPS. And, I suspicion that they did not use the latest high-sensitivity GPS receivers (e.g, SiRF StarIII) in order to meet the SPOT h/w price point of $149.
    #30
  11. TomW

    TomW Long timer

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    Well, I'm certain that consumer-grade GPS receivers aren't designed to be immune to overload from an enormous signal so close in frequency, particularly since running across a signal like that is normally extremely rare (CB/ham/2-way radio and cell phone transmitters are far-removed from the GPS band). The greater sensitivity of the new GPS receiver chipsets could make the Spot/GPS problem worse.

    Since Spot's GPS receiver is likely interfaced with the unit's controller, the GPS receiver is probably just turned off for the second it takes to transmit data to the GlobalStar satellite, thus avoiding freakish behavior resulting from overload. That's a much, much easier (thus cheaper) solution than providing a bulletproof 1.6gHz GPS receiver inside the same box with a 1.6gHz transmitter.

    Cheers.
    #31
  12. offroute

    offroute Been here awhile

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    Just returned and have captured all the data. I had tracking on continuously for more than 500 miles of varied terrain. Will create a GPX and KML file so everyone here can see where the drop outs occured. Should have this up by tomorrow. Gotta catch up on some work first...
    #32
  13. offroute

    offroute Been here awhile

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    http://www.gpxchange.com/fileinfo/index.asp?ID=104268&return=home

    The link will take you to my site, GPXchange.com, where I have imported a file that shows SPOTs performance over a 4 day riding period. The routes ridden are depicted as red tracks. SPOT was setup to send out "TRACK" messages every ten minutes during the riding. These "TRACK" locations are depicted as blue push pins and I have set up the file to label them with the time stamps when they were successfully relayed out throught he SPOT system. If you view the map and zoom in to a map width of 7.5 miles or less, you can follow these time stamped points around each route and find the gaps where the SPOT "TRACK" locations were not successfully relayed.

    The green push-pins are locations where I sent out "OK" messages.

    You can also use the Download KML link from the file info page to see this data in Google Earth, or you can download the GPX to view the data in your own local GPX capable application.

    I'll try and update this file later and add red push pins to the routes where SPOT should have relayed messages out, but was unsuccessful. I'll do this by using the timestamps on each tracklog and locating the points where 10 minutes had elapsed from the previous points.

    Hope this help you all in getting a clearer picture of how SPOT performs in an adventure riding scenario.

    Summary: Approx 2/3 of my TRACK messages were successful. 90% of my OK check-ins were successful. I can email a spreadsheet to anyone who wants the data in Excel format.
    #33
  14. TomW

    TomW Long timer

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    Great work. Thanks.
    #34
  15. Starblazer

    Starblazer n00b

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    I got one a few days ago. I have been using it for a few days just around the local area. Seems to work fine, I just came back from Max BMW in NH round trip 150 miles on two different routes. The unit tracked just fine. I got the unit for a trip to Alaska next May, to give the better half a way to know that I am ok. As for functions, once the unit is activated you can go to the web site and for the HELP and OK check in you can type in your own message. HELP is 90 letters and OK is 100. I have added up to four contacts emails, cellphone numbers for contacts. They all have worked just fine
    #35
  16. Starblazer

    Starblazer n00b

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    I just got on, I first tried it from in a window in the house sitting about 2 feet back. It sent the message just fine. In using it along the roads today in some good tree cover it seemed to still sent the location out.

    #36
  17. markgsnw

    markgsnw WTF?

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    #37
  18. klebel

    klebel Been here awhile

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    Well this blows it for me! I was hoping to pick one up for my trip from Seattle to Prudhoe Bay, AK next August. If it can't go any higher than N52 it is pretty much useless for me. I need it to go up to N70! :D
    #38
  19. klebel

    klebel Been here awhile

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    If you bought it for Alaska return it. It won't go up to that latitude. :deal
    #39
  20. TomW

    TomW Long timer

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    Not necessarily useless. Just because the satellites don't go that far north, they can still 'see' quite a ways north of N52 (the horizon is a long ways off at 1,000 mi up) -- you'll just need a view of the southern sky. And Spot will still cover most of the trip in its primary service area (see the coverage map at: http://www.globalstarusa.com/en/content.php?cid=300).

    Cheers.
    #40