optimum cutoff mask

Discussion in 'Global Navigation Satellite Systems' started by Frank, Dec 6, 2014.

  1. Frank

    Frank Guest

    Is there an optimum number of degrees to use in the cutoff mask? I use 5 degrees, and always kind of wonder if I may be degrading my solution by going too low.

    I'm setting up control points, so I need to be very accurate (~1 centimeter PP, 1 decimeter real-time). The only NTRIP caster that I have access to is 65km away, and the RTK corrections from that distance are just not as accurate as I need them to be.

    I'm using an Ashtech PM800 and SURVCE field software. GPS & GLONASS, L1 & L2.

    Thanks,
    Frank Looper
     
    Frank, Dec 6, 2014
    #1
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  2. Frank

    Sam Wormley Guest


    5 degrees is a good number -- there are plenty sats available.
     
    Sam Wormley, Dec 7, 2014
    #2
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  3. Until you can free youself from semi codeless algoritms (using L1/L2 P(Y) diferences to calculate iono errors), a 5 degree mask is important. That's because acquiring the P(Y) signals is very difficult with a satellite that is too close to the horizon. Once we can move on to using L1 + L2C or L1 + L5 (all civilian signals) then we should be able to eliminate the masking angle all together and let your receivers use all satellites in view.
    This should be doable before 2020 (L1 + L2C). First need L2C to become a fully healthy signal.
     
    Marcelo Pacheco, Dec 8, 2014
    #3
  4. Frank

    Alan Browne Guest

    Given your requirements I'd lift the mask to 10 or 15 degrees. I'd
    assume the receiver and/or antenna manufacturer(s) should give the best
    advice.



    --
    << Among Broad Outlines, conception is far more pleasurable
    than “carrying [the children] to fruition.”
    Sadly, “there’s a high infant mortality rate among
    Broad Outlines—they often fall prey to Nonstarters.” >>
    "Bestiary of Intelligence Writing" - CIA
     
    Alan Browne, Dec 8, 2014
    #4
  5. Frank

    Alan Browne Guest

    You'd still want to mask out the low sats for precision work as the OP
    is specifying.

    The best people to answer him are Ashtech.


    --
    << Among Broad Outlines, conception is far more pleasurable
    than “carrying [the children] to fruition.”
    Sadly, “there’s a high infant mortality rate among
    Broad Outlines—they often fall prey to Nonstarters.” >>
    "Bestiary of Intelligence Writing" - CIA
     
    Alan Browne, Dec 8, 2014
    #5
  6. Frank

    Frank Guest

    In my experience, Ashtech support has been worse than useless.
     
    Frank, Dec 30, 2014
    #6
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