## Bulge Calculation

This section is for general discussion about Gadgets

### Bulge Calculation

Hi all,

Looking for some help. before I do the deep dive on spending a bunch of time, I would ask... I am looking for the formula to calculate arc bulge. Anyone out there crossed that bridge?

This is what I have so far:
Code: Select all
`function BulgeCalculator (Rad, Ang)    return math.tan (math.rad(Ang) * Rad)end`
Thanks,
Jim

jimandi5000
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### Re: Bulge Calculation

Hi,

I wrote this and ran 30 to 40 test. I am thing it is working.

Code: Select all
`function Arc2Bulge (p1, p2, Rad)     local chord = math.sqrt(((p2.x - p1.x) ^ 2) + ((p2.y - p1.y) ^ 2))    local seg = (Rad - (0.5 * (math.sqrt((4.0 * Rad^2) - chord^2))))    local bulge = (2 * seg) / chord     return bulgeend`
Thanks,
Jim

jimandi5000
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### Re: Bulge Calculation

Not exactly sure what you mean by bulge, but I interpreted it to refer to circular segments. This may help you validate the results of your existing function.

https://en.wikipedia.org/wiki/Circular_segment

Van
vgraves
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### Re: Bulge Calculation

Hi Van,

Thanks for the reply. Here is what the SDK states on page 95.
Attachments
Thanks,
Jim

jimandi5000
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### Re: Bulge Calculation

In geometry, the "bulge" is called a sagitta. Surveyors sometimes calculate the sagitta to use when staking out arcs.

If you know the radius and chord length of the arc, here are two links with the formula to calculate the length of the sagitta.
https://www.mathopenref.com/sagitta.html https://www.liutaiomottola.com/formulae/sag.htm

If you know the radius and the angle of the arc, here is a link with a formula to calculate the length of the sagitta.
https://planetcalc.com/1421/
Bob Armbruster
www.ArmbrusterCo.com
armbrusterco
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### Re: Bulge Calculation

Hi armbrusterco,

Not sure I agree. the SDK states
The bulge represents a ratio between the chord length of an arc and its height (bulge = (2*arc_height) / chord_length).
So you are somewhat correct we do need the sagitta but we need the ratio to the chord to the sagitta.

Thoughts?
Thanks,
Jim

jimandi5000
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### Re: Bulge Calculation

You are correct. I missed the ratio. Oooops.
Bob Armbruster
www.ArmbrusterCo.com
armbrusterco
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### Re: Bulge Calculation

No Problem... I am just trying to learn as much as I can...
Thanks,
Jim

jimandi5000
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