Create Combined Curve of type Spiral, Arc, Spiral

(This functionality is available with the Computations module)

Creates a new combined curve by specifying its tangent lines and various combinations of parameters. The parameters that need to be specified depend on the type of combined curve to be created and the technique chosen. The technique you choose will depend on which parameters are known.

To run this option, select the Create/Combined Curve and Method/Spiral, Arc, Spiral from the Computations task to display the relevant dialog box.

Before using this command, check the Configure/Alignment command and ensure you have the required design constants set.

The combined curve to be created will be given the attributes currently defined via the Attributes/Line command, and the associated points created will be given the attributes currently defined via the Attributes/Point command. You should use these commands to set the required attributes before creating any combined curves.

Important: Refer to the Creation Methods-Special Notes topic and ensure that you are familiar with its contents.

Create Combined Curve

Item	Used to
Type	Select the type of combined curve required. You may select from Spiral in, Arc, Spiral Out Spiral In, Spiral Out Spiral In, Arc Arc, Spiral Out
Technique	Select the technique to be used in computing the chosen combined curve type. The relevant techniques depend on the spiral type, and they are all shown in the list box. Simply select the technique that suits the known parameters, or if you know redundant parameters, select the technique that you prefer.
Point ID	Key in the point identifier to be assigned to the first new point created in the process. Other new points will get the next available identifier.
Tangent Line 1 & Tangent Line 2	Optionally select the tangent line with the mouse or key in the line number. If you select the line with the mouse (recommended), the reference points defining the selected line segment will automatically be placed in the Reference Points field. If however you key in the line number, you will still have to complete the Reference Points field. Note that you do not have to complete these tangent line fields, as just completing the reference points fields defines the tangents. Use the reference Points fields and not the Tangent Line fields if you do not want the combined curve inserted into a line object.
Reference Points (for each tangent line)	Specify the tangent line by two points. If you selected the tangent line in the Tangent Line field with the mouse, the Reference Points field will already be complete.
Fillet Lines	Select this option to have the tangent lines filleted at the tangent points when the combined curve is accepted. This will cause the tangent lines to be truncated or extended as the case may be, such that they end at the tangent points. If a tangent line extends through the tangent points and the fillet option is not selected, it will be broken into two new lines that meet at the tangent point.
Interpolate Elevations	Select this option to interpolate elevations at the newly created tangent points.
Intersection Angle	Display the Intersection angle of the combined curve after the Compute button is selected.
Parameters	Enter or specify the values of the parameters required to compute the combined curve. Depending upon the technique selected some of the following edit fields will be enabled and others will be disabled.  The fields that are enabled are the required input parameters for the technique selected.  The disabled fields will be filled out when the combined curve is computed. Radius: The minimum radius of the spiral and/or arc. Tangent In: The distance from the tangent point on Tangent Line 1 to the intersection point. Tangent Out: The distance from the intersection point to the tangent point on Tangent Line 2. Spiral In: The spiral length from the tangent point on Tangent Line 1. Spiral Out: The spiral length from the tangent point on Tangent Line 2. Velocity In: The maximum velocity permissible along Spiral In. Velocity Out: The maximum velocity permissible along Spiral Out. Note: The velocity is calculated based upon the parameters set in Utilities/Configure/Alignment.
Compute	Compute the combined curve and display it on the screen. All the relevant combined curve parameters (velocities, spiral lengths etc.) will be displayed in the dialog. If any unusual circumstance occurs in the creation of the combined curve, a warning is also displayed on the dialog indicating the problem. For example, if the curve does not fit between the tangent lines entered, 'Warning - Curve beyond Reference Points' is displayed.
Accept	Save the computed combined curve to the database. Note that if the tangent lines were part of an alignment, the alignment is automatically modified to be along the new combined curve.
Next	Find the next available Point ID in the data base.  This field is active when the Point ID edit field has the focus.
Last	Find the last available Point ID in the data base.  This field is active when the Point ID edit field has the focus.