Spiral Curve

This command plots a spiral curve. The user must provide the P.I. (point of intersection), the length of spiral and the radius length of the simple curve. The command will plot a symmetrical spiral or a spiral in or spiral out (choose the S option for the first prompt if you only want to plot a spiral out). If you have an unsymmetrical spiral then plot a spiral in using the T or P option then use the S option to plot the spiral out. The command plots a polyline to represent the spiral as line segments at the resolution specified by the user. You can use the Calculate Offsets, Station Polyline/Centerline or Offset Point Entry commands, found in the Centerline menu, to calculate points and/or stations and offsets from the spiral.

Prompts

Spiral method [TS/ST/<PI>] press Enter
PI Point ?
Pick point or point number: pick intersection of tangent lines
TS Direction point (tangent in) ?
Pick point or point number: pick point along tangent in line
ST Direction point (tangent out) ?
Pick point or point number: pick point along tangent out line
Tangent in direction= N 56d24'9" E Azimuth= 56d24'9"
Tangent out direction= S 65d9'1" E Azimuth= 114d50'59"
Overall Delta= 58d26'50"
Point calculating distance resolution <10.0>: press Enter
Length of Spiral <350.0>: press  Enter
Radius of simple curve (precede with - sign if curve to left) <954.93>: 954.93
Degree of curve: 6d0'0"
Theta of Spiral= 0.18325951 (radians) 10d30'0" (dd.mmss)
Distance along tangent line from TS to SC= 348.82
Distance offset from tangent line to SC= 21.33
(k) Shift along tangent line of PC= 174.80
(p) Shift offset from tangent line of PC= 5.34
Distance from PI to TS= 712.00
North(Y) of TS= 4583.08 East(X) of TS= 4244.46
North(Y) of SC= 4758.34 East(X) of SC= 4546.82
North(Y) of Offset PC= 4675.36 East(X) of Offset PC= 4393.02
[P]lot spiral or
[I]ntermediate distances for staking (deflection angle calc) <P>: press  Enter
Point calculating distance resolution <10.0>: 5 Enter the resolution at which you would like the line segments of the representative polyline plotted.
North(Y) of Radius Pt= 3879.96 East(X) of Radius Pt= 4921.44
<press [Enter] for symmetrical spiral out>/[D]elta of simple curve: press  Enter If you want a spiral in only enter D then input the delta angle of the curve.
Simple Curve Delta= 37d26'50" Length of Arc= 624.12
North(Y) of CS= 4805.10 East(X) of CS= 5158.11

Pulldown Menu Location: Draw > Arc
Keyboard Command: spiral
Prerequisite: For a symmetrical spiral, draw the tangent in and tangent out lines. For spiral in or out only, draw the tangent line in or out.