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    Re: A practice round of stars
    From: Jeremy C
    Date: 2013 Mar 5, 06:02 -0800


    Thanks for the nice explanation and plot. I agree with much of your reasoning, and you did a great job with the 3 LOP's you reduced. I have never moved LOP's mathematically, relying on plotting when I do so. You are right however, at that speed and in that time frame, it really doesn't make much of a difference.

    The moon is indeed the most difficult body from which to obtain a good LOP. In this particular case, it was the second worst of the bunch, but with a GPS-AP intercept of -0.5' it is still a good sight. The Temp/Pressure was included for those who would use the moon, as at 13 degrees, it does make a difference, at least to my thinking.

    I will clear up one false assumption that you made. I work on a merchant ship about 200 meters long. While we have a magnetic compass, we only use it in emergencies. We have a standard gyro compass for heading, but more importantly, I don't use the compass at all when I give "course" in these problems. I note over several minutes the Course made good via GPS, so I get the most accurate picture of the ship's actual motion over ground. You can therefore always assume that "course" in these problems is a true course with no need for correction.

    Again, an excellent job with the reduction, and I do hope that you work out the second problem I posted. It will have a better spread of bodies.

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