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    Re: On the integration of location and data
    From: George Huxtable
    Date: 2009 Nov 3, 10:13 -0000

    Frank Reed reminds us of an earlier thread "Learn the stars, by phone", that
    he started on 13 May this year. I am surprised that he does so. New readers
    would be well-advised to follow that thread, to see where it led to.
    
    He writes- "Yes. Augmented reality! This is the cool development in
    smartphone technology I was talking about last spring that we could leverage
    very easily for celestial navigation education (here's a link to a message
    of mine in that earlier thread: http://fer3.com/arc/m2.aspx?i=108258). "
    
    ===========================
    
    It turned out that Frank's claims for the precision of such devices, which
    relied on the local magnetic field, were based on early statements by
    Celestron of the pointing-precision of their "Skyscout" viewer. Frank quoted
    a pointing precision of half a degree, which was then challenged as
    implausible. And by that time, Celestron's claimed precision had been well
    watered-down to 3 degrees, which corresponds to an area of sky which would
    contain 36 times as many stars as before. That made a lot of difference. If
    you pointed it at Jupiter, it might identify it as Jupiter, but might just
    as well identify it as one of several other-bodies, within that
    3-degree-radius circle. As it kept many thousands of stars in its
    memory-locker, that would be all too likely.
    
    He now invites us to look again at his earlier posting, without drawing
    attention to any such defects.
    
    This time, he adds- "The article doesn't mention that this technology
    depends not just on location data, but also on orientation data which
    generally implies a built-in magnetic compass. There's a way around this in
    major cities if you use some sophisticated processing (which can occur
    server-side) to take the image, the GPS (or wifi) location data and then
    figure out direction based on the buildings seen and maybe even using
    shadows if it's daytime. That combined with the simple inertial sensors in
    many phones would yield orientation without a magnetic compass."
    
    That notion seems even more implausible than the previous one, for viewers
    of the night sky.
    
    He ends his gee-whizzery with - "And now we just need someone to write some
    applications that feature the celestial navigation data prominently."
    
    It seems to me, we need someone to invent a way of getting some
    pointing-precision first, before we concern ourselves with such
    applications. I don't say it's impossible. Maybe, some day, ring-lasers will
    be made that can go into a pocket. But not yet; not with sensors that rely
    on the local magnetic field.
    
    George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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