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    Re: Simulating platform instability on land?
    From: Greg Rudzinski
    Date: 2013 Jul 18, 12:48 -0700

    Peter,

    The best thing to do is befriend a sailor and join the crew. Bring a sextant along and grab some sights along with GPS positions.

    Ships are reasonably stable even in rough weather so there is no need to simulate. Small craft is something all together different. When on a small craft it is very important to make the observation when on top of the swell. Try to be standing so that the legs can compensate for some of the motion (like a surfer). Simulating this is easier said than done. Perhaps taking sights from a canoe to a short horizon would work if a river or lake is near by. A swing or hammock might work.

    Greg Rudzinski


    Simulating platform instability on land?
    From: Peter Monta
    Date: 2013 Jul 18, 02:20 -0700
    I've been taking some sextant sights recently, on land, and I'm wondering how I might simulate being at sea, to experience taking sights under those conditions. (This is with lunars, so I can get by without a sea horizon. Mostly I'm interested in getting a feel for what sea sights are like, and how accuracy degrades versus terra firma.)

    The idea would be to stand on a platform that's being moved around, either by an assistant or by motors/actuators. It would be nice if the motion could be dialed from "calm" to "stormy". Where can I find model parameters, or actual time-series recordings, of the orientation of the deck underfoot under various weather conditions and type of craft? This must be well-known stuff, but my searches aren't coming up with much.

    I've read that sextant users at sea anticipate the swells. Would platform orientation include a large Fourier component representing the swell, plus a smaller noiselike component?

    Of course hopping on a boat would be an option, but the hassle factor is much higher (for me anyway), and the conditions are less controllable.

    Cheers,
    Peter

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