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Re: Pointless? Optimisation - Intercept Plotting
From: Paul Hirose
Date: 2019 Feb 4, 12:06 -0800

On 2019-02-04 9:01, Tony Oz wrote: > One thing still is not yet clear - the scale to use as an intercept distance can not be placed on the protractor directly - because that scale depends on the latitude. Do you do an extra calculation - to convert the T|A miles into the millimeters on the protractor's (DIY) scale? If the plotting sheet scale is 1 mm per mile, or 2, 5, etc. it's easy to mentally compute the distance to move the protractor toward or away. However, the movement requires a straightedge graduated in millimeters since my square protractor (purchased from Celestaire, I think) has its edges graduated in degrees, not millimeters. I have never tried it, but I think you could use dividers if you have enough coordination to handle the protractor and straightedge with one hand. I agree with Michael Bradley about the "bearing markings on its edge which confuse matters." To move the protractor toward or away, one must be careful to match the 90 degree mark (for example) on the square protractor to the correct millimeter mark on the straightedge. There would be less chance of a mistake if the protractor scale was a circle, and only the 0, 90, 180, and 270 degree lines extended to the edges. What you actually have in the interior of the square protractor is a grid of 5 mm squares. I have never figured out a use for this grid. Anyone?

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