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    Re: Estimating height of eye
    From: Marcel Tschudin
    Date: 2013 Apr 11, 19:38 +0300

    Thank you, Richard Langley, for providing this information and giving
    an idea on the sort of attainable accuracy with consumer products.
    
    Marcel
    
    On Thu, Apr 11, 2013 at 3:48 PM, Richard B. Langley  wrote:
    > ________________________________
    >
    > Sorry for being late in providing more information but the life of a prof is
    > a busy one, well, at least for me. You want to determine a height difference
    > of a few metres at the same location with an accuracy of hopefully 10%. If
    > the height difference is 3 metres, say. then you are looking for 30 cm, one
    > sigma. Then you will need to make carrier-phase measurements using a
    > survey-grade GNSS (GNSS = global navigation satellite systems, including
    > GPS, GLONASS, etc.) receiver and process them using either the precise point
    > positioning technique or double-differencing with respect to a reference
    > station. I think pseudorange measurements are just too noisy to give you the
    > desired accuracy even in differential mode.
    >
    > Attached are a few slides from my external Differential GNSS Course (to be
    > given next in Nashville in September at the ION meeting). The first shows
    > the different kinds of positioning available with GNSS, then horizontal and
    > vertical positioning accuracies with standalone pseudorange measurements
    > (like those used by handheld receivers) but as determined at some FAA
    > monitoring stations, then WAAS-corrected position accuracies using the same
    > stations.
    >
    > To get back to celnav, I will have to determine the height of my eye when I
    > go to the Big Island of Hawaii a couple of weeks from now at a house up from
    > Kona with a nice view of the Pacific. I'll do some GPS height averaging but
    > as I'm just taking my plastic Davis sextant, I'm not looking for high
    > accuracy, just a bit of fun, to break up the monotony of sitting around the
    > pool. ;-)
    >
    > -- Richard Langley
    >
    >
    >
    >
    > On 2013-04-10, at 3:45 PM, Marcel Tschudin wrote:
    >
    >>
    >> {at} Richard Langley
    >>
    >> I noticed from your contributions and publications that you seem to be
    >> more deeply involved in the subject of GPS. May I therefore ask you:
    >> Do you have an idea on the sort of accuracy one may "generally" expect
    >> when measuring with GPS at the same location (few tenths of meter
    >> distance) height *differences* between about 2 and 5 m ? Would it be
    >> possible to measure at the two locations the height and obtain their
    >> difference to about +/- 20% or even better to e.g. +/- 10% and what
    >> type of equipment would this require?
    >>
    >> Thanks in advance for some hints.
    >
    > [[rest snipped]]
    >
    > -----------------------------------------------------------------------------
    > | Richard B. Langley                            E-mail: lang---ca         |
    > | Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
    > |
    > | Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
    > |
    > | University of New Brunswick                   Fax:      +1 506 453-4943
    > |
    > | Fredericton, N.B., Canada  E3B 5A3
    > |
    > |        Fredericton?  Where's that?  See: http://www.fredericton.ca/
    > |
    > -----------------------------------------------------------------------------
    >
    >
    > Attached File: 123517.slides_from_ion_dgnss_course.pdf (no preview
    > available)
    >
    > View and reply to this message: http://fer3.com/arc/m2.aspx?i=123517
    

       
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