What's is Grad for the conversion of longitude?

Question

I am faced with the problem of converting angles, such as latitude and longitude, to linear measures, such as meters or feet. They mentioned in passing at:

http://www.math-solutions.org

that the angles must be expressed in term of grads before they can be used in any of the formulas. So, just what is a Grad, anyway?

Thanks very much in advance.

Regards,

Hans

Answer 1

Another way to figure out the distances is to use the "Great-circle distance" equation.

http://williams.best.vwh.net/gccalc.htm

Or, if you want to figure out the equationt to program it into your calculator:

http://en.wikipedia.org/wiki/Great-circl...

Answer 2

In angle measurement, a GRAD is short for a gradian

There are  400 gradians in a circle

(divides each right angle [90°] by 100)

not very widely used except by surveyors