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    Increased dip for "Nearer" Horizon or Level Line
    From: Bruce J. Pennino
    Date: 2011 Jul 25, 20:22 -0700

    Hello,
    I'm learning CN and also how to use a sextant. I have two questions for this knowledgeable group. First: I live near a large reservoir where I can walk down to the water's edge. I can view several directions, and trees have been removed from the banks . After doing a little trig and geometry, I've concluded that I can us the shoreline as a horizon, but I must use increased dip correction depending on distance to opposite shore. Can someone please confirm these results for a 6 ft eye height? At 30,000 ft to opposite shore line, use a standard dip correction of 2.3 minute of arc. At 20,000 ft, use about 3 minutes. At 10,000 ft use 4 minutes; and at 5,000 ft use 6 minutes for dip. Correct I hope? Practical?

    Second question: I have a laser level, high quality Nikon construction level, and a surveyor's total station. The total station has an internal scale that I can estimate a vertical angle to plus or minus about 2.5 seconds. Can I use these instruments to establish horizontal lines on a wall?

    Thanks for help. I'm learning a lot!

    Bruce P.
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