Spectra Precision Survey Pro CE v3.6 User Manual - Manual (Page 354)

Curve Menu
R-197
Spiral
&XUYH 6SLUDO 
The Spiral screen will compute the details of a spiral curve, given the
spiral length and radius.
Spiral length : is the length of the spiral curve.
Radius : is the circular curve radius.
6ROYH : computes the details of the spiral curve.
/D\RXW« : accesses the Spiral Layout screen
(Page R-198) where the location of stations on
the spiral curve can be computed.
7UDYHUVH« : accesses the Traverse on Spiral
screen (Page R-199).
Results
X of Throw : is the distance along the tangent where a perpendicular
line intersects with the radius point.
Y of Throw : is the minimum distance between the tangent and the
extended circular curve.
X : is the distance from the TS to the SC along the tangent.
Y : is distance from the SC to the tangent.
Delta : is the angle between the tangent, and the line between the PI
and SC.