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    Re: Estimating height of eye
    From: Marcel Tschudin
    Date: 2013 Apr 10, 19:17 +0300

    Thank you, Brad, for finding this Android app for me. I presume that
    the 1 m represent an absolute accuracy and that measurements of height
    differences may possibly attain a higher accuracy. I will give this
    affordable gadget a try and perform some tests with it.
    
    Marcel
    
    
    On Wed, Apr 10, 2013 at 6:28 PM, Brad Morris  wrote:
    > ________________________________
    >
    > Hi Marcel
    >
    > There is an app in the Android market called "Precision GPS Pro".  The cost
    > is US$0.99
    >
    > It claims a 1 meter elevation accuracy after averaging, although they do not
    > indicate how long an average you require to achieve that.
    >
    > The free version of this app does not do elevation averaging.
    >
    > I have not tried this app.
    >
    > Brad
    >
    > On Apr 9, 2013 6:21 AM, "Marcel Tschudin"  wrote:
    >>
    >> ________________________________
    >>
    >> In my sunset observations the guesstimates for the HoE of probably not
    >> better than +/- 20% are indeed a weak point. But how weak? The dip is
    >> proportional to the square root of the HoE which means that the
    >> estimated dip error is only half of the estimated HoE error. For the
    >> average HoE of 3.5m the "normal" dip is 3.3 moa and a 10% error of it
    >> therefore +/- 0.33 moa. This corresponds in the photo to slightly more
    >> than one pixel which is 18 seconds of arc.
    >>
    >> Frank, you mentioned estimating HoE within about +/-5%. I'm wondering
    >> whether you would also be able to attain such an accuracy by climbing
    >> over the rocks as shown in my photo:
    >>
    >> 
    https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=b33d2c81ba&view=att&th=13ddab531282f2e7&attid=0.1&disp=inline&realattid=f_hf5h7cfp0&safe=1&zw&saduie=AG9B_P-DvbGAuAxTxtruQd29-avq&sadet=1365502394438&sads=w4N-7jPt0vbdfN6eZHKSEaR8vQ0
    >> For my average of 3.5 m this would correspond to less than 20 cm or
    >> what might be more familiar to you to about half a foot.
    >>
    >> In order to verify my guesstimates I do indeed consider to perform
    >> some additional measurements. I'm wondering how good I could measure
    >> it using GPS and also the Russian version of it. I have no experience
    >> in using these systems. I understand that I would have to measure both
    >> levels, eye and sea level and then take the difference. Is there an
    >> Android application which I could load on my Samsung pad allowing to
    >> collect measurements over a longer time period which then calculates a
    >> mean altitude and its standard deviation? What are the sort of result
    >> one could obtain this way?
    >>
    >> Marcel
    >>
    >> View and reply to this message: http://fer3.com/arc/m2.aspx?i=123477
    >
    > View and reply to this message: http://fer3.com/arc/m2.aspx?i=123498
    

       
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