# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: An azimuth nomogram: what's under the hood?
From: Bob Goethe
Date: 2018 Mar 13, 09:34 -0700

>>I wonder how could I re-calculate positions of each and every angular mark along each scale<<

CorelDraw is a vector drawing program.  The full application, available for \$615 Canadian, allows you to create drawing elements using macros written in VisualBasic code.  So you can calculate the value of a function, and tell the program to insert a line or a dot at that point.  I used this to create the scales for the slide rule project I was developing (a project which has gone into dormancy, alas; I hope to come back to it this year).

In any case, I produced the slide rule scales using For...Next looping code.  It took a little while to write the code/equations, but once I had it I would click to execute and WHOOSH, the entire D-scale, for instance, would appear on the page.  VisualBasic, of course, has a bunch of trig and other mathematical functions it can work with.

Alas, my version 13 of CorelDraw turned out to be incompatible with Windows 10.  I ended up buying a brand new \$119 CDN "Home and Student" edition which does everything the full version does...except that it lacks the macro programming capability.  So I have lost the ability to create drawing elements using VB macros.

I recently set out to recreate a VPOS universal plotting sheet to fit on an 8.5 by 11 inch page, and made the compass rose bigger than is typical.

Building the compass rose itself took less than 5 minutes.  Draw a line.  Set the rotation point to the center of your intended circle.  Tell the program to produce 359 copies of the line, each time rotating it by 1°.  Create a little bit longer lines and get them duplicated at 5° intervals, and so on.

It took a bit of time to put the labels at various points around the circle.  But still, the entire rose took only 45 minutes to build, labels and all.

But getting that scale for longitude distance in the lower right corner of the page was quite tedious, and took me quite some time to lay out.  I reflected in the end that I should have simply bought the full version of CorelDraw, and used macros to lay out the points needed in that drawing.

If you buy the full CorelDraw product, and can work out equations to define the parabola and where the marks go, you can automate the production of a drawing.  An advantage of this is that the marks that appear on the parabola will be placed with mathematical precision that goes out to many, many decimal places.

Bob

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