Re: Curvature Calculator

[James Robinson <wascana@my-deja.com>]

trainman@ozemail.com.au wrote:

> If anyone understands how the Americans do their curve calculations,
can you
> please test the calculator and let me know if I got the formulae
right?  Thanks.

The formulae appear correct, but I should make a couple of comments:

- There may be some confusion with your use of "chains" as one of the
parameters, since there are two types of chains:  The Ramden chain is
100 feet long, and the US Survey or Gunter's chain is 66 feet long.
Most surveying in the US is done using a 100 foot chain, and curve
measurement, when described by radius, is usually quoted in feet and not
by chains.  Yes, chains are understood in Australia, but there could be
some confusion to those not saavy with the differences.

- There are also two methods for calculating the degree of curvature
using the "American System". The one you have described uses the 100
foot chord method, but there is also a metric method that is used in
Mexico (not referring to Victoria, by the way) and parts of South
America.  In the metric version a 20 metre chord is used as a basis, so
the degrees work out to about 2/3 that of the 100 foot chord method.
Since you have shown metres in your calculator, this might lead to
confusion.


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