How are arcs usually dimensioned in drafting?

Answer 1

Any two parameters will define an arc, but most common are:

Arc Length (L)

Radius (R)

Central Angle (CA or the 'delta' symbol, which I cannot reproduce, here.)

In surveying, the Long Chord (LC) is sometime used, giving the bearing and distance from the arc beginning to its ending.

Also, in highway and railroad work, the degree of curve (g), or 'sharpness of the curve are specified. If you use 'g', be aware that the equation for highway 'g' is not quite the same as 'g' for railroads. (Highway factor for 'g' is 5729.58, while the railroad factor for 'g' is 5730.00)