This command allows you to enter new centerlines, as well as recall and edit existing centerline files. Centerline files in SurvCE are ASCII files with a .CL extension. When the routine is selected, a dialog will appear in which you can load existing centerlines or begin entry of new centerline information.

Clear: This icon, at the top of the screen, clears out all information in the dialog in preparation for entering a new centerline. With no centerline file loaded or saved yet, the file name in the upper left is displayed as “None.”
- Start Pt ID: If the centerline starts on a point number that exists in your current coordinate (.crd) file, you can enter the point number here, and it will recall and display the starting coordinates. The point can also be selected from the list or map using the appropriate icons.
- Start Station: You must enter the starting station for the centerline. (“Station” is the same as the European term “Chainage.”) Many surveyors and engineers prefer not to start centerlines at station 0. If the job backs up or needs to start further back along the centerline, this method will leave you with negative stationing. There are three centerline “forms” as set in Job Settings, Units. A starting station of 1500 can be displayed as 1+500 (metric, US-style, showing whole kilometers left of the “+”), as 1500.000 (pure decimal chainage, common to Europe), and as 15+00 (feet, US-style, sometimes also used on metric roads in Canada), often referred to as “station 15 plus 00”. In all cases, you would enter it as 1500, but it would display in the correct format after pressing Enter. For example, you would see 1+500.0000 if configured to kilometers. The program will also accept use of the “+” in the entry of the station, and will convert to the configured form after you press Enter.
- Northing, Easting: If the northing and easting are not recalled from a starting point number, you will need to enter the northing and easting for the start of the centerline. It is not necessary to enter the northing and easting if you use the Pick PL (pick polyline) option for defining a centerline, since the starting coordinates of the selected polyline are automatically used, and would overwrite anything previously entered.
- Load: This command allows you to load an existing centerline for review or edit.
- Edit: Use this button to edit the highlighted element.
- Delete: Use this button to remove the highlighted element.
- Add: Returning to the starting dialog, you can add elements to get a centerline started. Typically, you will start with a line or tangent segment, but you can also start on a curve or spiral curve element. When you select Add, you get to choose which element to use. These options include:

- Add (Line): A tangent section of the alignment. This option allows you to enter a point ID or coordinates to define the end of the tangent, or enter the station, or distance and the direction. To force the element to be tangent to the previous element, toggle on the Tangential to the previous elem option. This will gray out the direction field and will compute the tangent direction and enter it for you.

- Add (Curve): A typical circular curve section of the alignment. The first element of the curve defines what the options for the second element can be (See Lists Below). The RR toggle allows the user to use Railroad definitions. The Review button allows you to verify the Tangent In and Tangent Out bearings or azimuths (depending on Job Settings, Format, Angle Display settings), as well as confirm PC and PT coordinates. For example, this allows you to verify computed Tangent Out bearings against paper plans, before continuing entry of new elements.


- Add (Spiral-Curve-Spiral): The Spiral-Curve-Spiral element is really just two implementations of Spiral Only (line-spiral-curve and curve-spiral-line). The advantage of Spiral-Curve-Spiral is that it completes three elements at once and is a fairly common application on high-speed highways. This routine also allows the user to define the spiral-curve-spiral using known points as long as the spiral in and spiral out lengths are entered first.


- Add (Spiral Only): The Spiral Only element will handle a spiral between any line and arc segment (e.g. line-spiral-arc or arc-spiral-arc).

- Pick PL: This option is only visible if you Clear the dialog. With this option, you can pick a centerline from any screen polyline, including polylines with arcs. When you choose Pick PL, you are immediately presented with the graphic screen, where you can pan by dragging your finger across the screen, or zoom using the many zoom options. You can choose not to select a polyline (maybe there were none to select!) by pressing OK or Enter. When you select a polyline, it will highlight as a darkened polyline. After selecting a polyline and pressing OK or Enter you will see the polyline elements. Note that if you change the start station to 500, all the stationing for the polyline elements will change accordingly. This is also true regarding the starting northing and easting. If these are changed, all element coordinates will change accordingly, as can be verified using the Edit option.

- EQ: The EQ button allows you to enter station equations.

- Save As: This saves the file. Enter a name.
Note: You can create new points with Input-Edit Centerline. When you enter and save a centerline, it will prompt “Do you want to save centerline points?” You may answer Yes and save point IDs for the start, end, PI, PC, radius point, PT and any key spiral points found in the file. In the same way, a centerline that you load can be re-saved with new coordinate ID’s assigned to all key points, as long as you make some change, like adding a point number to one of the Pt ID fields for a CL Element. If you answer Yes to Save Centerline Points, the dialog box below appears. If you have entered point ID’s of your own choosing in the Input-Edit dialogs, use the upper option. The lower option will auto-number from the starting point ID without regard to any numbers you’ve entered, but will respect and not overwrite used points in the file. Points are not stored to the centerline file itself, so after loading a stored centerline, no point ID’s will appear.
