• GPS above 60 degrees

    From David Lesher@21:1/5 to All on Tue Sep 21 23:55:24 2021
    A friend is engaged in a journey north, as in
    Resolute Bay, Nunavut 74.72N 094.97W

    I find papers about GPS coverage at ground level. Is there
    anything published about coverage at 20-30 thousand feet?

    --
    A host is a host from coast to coast.................wb8foz@nrk.com
    & no one will talk to a host that's close..........................
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433

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  • From Terje Mathisen@21:1/5 to David Lesher on Wed Sep 22 16:08:41 2021
    David Lesher wrote:
    A friend is engaged in a journey north, as in
    Resolute Bay, Nunavut 74.72N 094.97W

    I find papers about GPS coverage at ground level. Is there
    anything published about coverage at 20-30 thousand feet?

    I have been to Svalbard to visit three Degree Confluence Points, all at
    78N, so using a GPS far north was a primary reason for going there.

    The trip report starts here, you can see that I had very good coverage
    even in March 2004:
    https://confluence.org/confluence.php?lat=78&lon=16

    At those latitudes you have absolutely no issues with GPS coverage
    because you are seeing all the sats on the opposite side of the pole.

    In fact, I believe I read somewhere than around 55-60 degrees was the
    worst coverage for the GPS constellation, but by now we have at least GPS+Glonass+Galileo, and so far north you will see the chinese setup as
    well.

    Terje

    --
    - <Terje.Mathisen at tmsw.no>
    "almost all programming can be viewed as an exercise in caching"

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  • From David Lesher@21:1/5 to Terje Mathisen on Wed Sep 22 23:00:18 2021
    Terje Mathisen <terje.mathisen@tmsw.no> writes:

    I have been to Svalbard to visit three Degree Confluence Points, all at
    78N, so using a GPS far north was a primary reason for going there.

    The trip report starts here, you can see that I had very good coverage
    even in March 2004:
    https://confluence.org/confluence.php?lat=78&lon=16


    Ironically, they were headed to BGTL/Svalbard, but they were
    denied landing permission there.

    They now think their issue is their flight control system is
    upset by the 20 degree difference between magnetic and true
    north; this started at 73N.

    --
    A host is a host from coast to coast.................wb8foz@nrk.com
    & no one will talk to a host that's close..........................
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433

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  • From Alan Browne@21:1/5 to David Lesher on Fri Oct 1 16:05:02 2021
    On 2021-09-21 19:55, David Lesher wrote:
    A friend is engaged in a journey north, as in
    Resolute Bay, Nunavut 74.72N 094.97W

    I find papers about GPS coverage at ground level. Is there
    anything published about coverage at 20-30 thousand feet?

    No issues, although at ground level he might not get WAAS coverage.
    At altitude he should get WAAS as well.

    Even at 45° N, here, I see sats over Russia from ground level.


    --
    "...there are many humorous things in this world; among them the white
    man's notion that he is less savage than the other savages."
    -Samuel Clemens

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  • From Alan Browne@21:1/5 to David Lesher on Fri Oct 1 16:06:59 2021
    On 2021-09-22 19:00, David Lesher wrote:
    Terje Mathisen <terje.mathisen@tmsw.no> writes:

    I have been to Svalbard to visit three Degree Confluence Points, all at
    78N, so using a GPS far north was a primary reason for going there.

    The trip report starts here, you can see that I had very good coverage
    even in March 2004:
    https://confluence.org/confluence.php?lat=78&lon=16


    Ironically, they were headed to BGTL/Svalbard, but they were
    denied landing permission there.

    They now think their issue is their flight control system is
    upset by the 20 degree difference between magnetic and true
    north; this started at 73N.

    Should be using grid compass, not magnetic north that far north.


    --
    "...there are many humorous things in this world; among them the white
    man's notion that he is less savage than the other savages."
    -Samuel Clemens

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  • From David Lesher@21:1/5 to All on Sat Oct 16 12:51:29 2021
    It occurs to me that one of the systems could have put some/all
    of its birds in polar orbits. With such added to the mix,
    there's be no high-latitude shortcomings.

    Higher launch costs, however.

    Pondering if generic receivers could cope with them, or they'd
    fall over.



    --
    A host is a host from coast to coast...............wb8foz@panix.com
    & no one will talk to a host that's close..........................
    Unless the host (that isn't close).........................pob 1433
    is busy, hung or dead....................................20915-1433

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Terje Mathisen@21:1/5 to David Lesher on Sat Oct 16 22:08:49 2021
    David Lesher wrote:
    It occurs to me that one of the systems could have put some/all
    of its birds in polar orbits. With such added to the mix,
    there's be no high-latitude shortcomings.

    Higher launch costs, however.

    Pondering if generic receivers could cope with them, or they'd
    fall over.



    Really not needed: The current GPS constallation already provides
    _better_ coverage at the poles than they do a bit further south (north).

    The only thing that gets significantly worse as you're moving from
    southern Norway (58 degrees) to Nordkapp (71 degrees) is the vertical
    accuracy: Both horizontal position and time resolution stays more or
    less the same.

    Add in Glonass and Galileo and you'll get pretty good positional
    accuracy everywhere with a clear sky view.

    Terje

    --
    - <Terje.Mathisen at tmsw.no>
    "almost all programming can be viewed as an exercise in caching"

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  • From Alan Browne@21:1/5 to David Lesher on Sat Oct 16 18:32:50 2021
    On 2021-10-16 08:51, David Lesher wrote:
    It occurs to me that one of the systems could have put some/all
    of its birds in polar orbits. With such added to the mix,
    there's be no high-latitude shortcomings.

    Higher launch costs, however.

    Pondering if generic receivers could cope with them, or they'd
    fall over.

    There are no significant high latitude shortcomings for basic GPS
    service. At the north pole you have a ton of satellites in view.

    If you had 6 polar orbit satellites, then there would no coverage
    directly over the pole most of the time v. the existing constellation.

    I suppose you could low orbit these for more coverage some of the time,
    with more sats, or have more sats in the very expensive 12 hour orbit as
    well to improve things. But they're "good enough" as is.

    What you don't have is SBAS because those sats are geosynchronous
    meaning you need a really good "view" close to the horizon (in the icy
    wastes probably not a difficult thing...). IAC, the correction data is
    not done for extreme high latitudes.

    Generic receivers will receive any signal for which a PRN code is known
    to exist. Indeed SBAS satellites (WAAS, EGNOS, etc.) "emulate" the
    military C/A signal to transmit data to the receiver (this includes
    positioning data (WAAS) as well as correction data. Of course they use
    a PRN that is different from the US Air Force "set".


    --
    "...there are many humorous things in this world; among them the white
    man's notion that he is less savage than the other savages."
    -Samuel Clemens

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