90
Programs
Leica TPS800-4.0.0en
3. Spiral/Clothoid
A spiral is a transition curve whose radius changes
along its length. A spiral has to be defined by:
•
Start point (P1) and end point (P2) with known
easting and northing coordinates
•
Radius at the start of the spiral (R)
•
Spiral parameter (
) or length of the
spiral (L)
•
Direction: Clockwise or Anticlockwise
•
Spiral type: Spiral In or Spiral Out
P1
Start point
P2
End point
R
Radius
L
Length
Spiral types:
•
Entry spiral (Spiral in = A): Spiral with a radius of
infinity at the start and a given radius at the end.
•
Exit spiral (Spiral out = B): Spiral with a given
radius at the start and radius of infinity at the
end.
•
Partial/Ovoid spiral: A spiral with a given radius
at the start and another given radius at the end.
A
Entry spiral
B
Exit spiral
A = L · R
TPS800_Z129
R
R
L
P1
P2
TPS800_Z99
A
B
