Hands On Turn Chords, and Middle Ordinates layer files. Open the table for each layer and notice that the Chord Points table is fully populated while the other two tables are empty. 3. To make navigating around the map easier while working the exercise, several bookmarks were added to the map document. From the Standard menu, choose Bookmarks > Manage and select CR MP 0.0 1:500, located at the bottom of the list. The map zooms to the beginning of Chuckanut Ridge Road. Notice that the road contains many vertices, typically spaced less than 20 feet apart. Modeling these curves requires carefully densifying the polyline. Carefully inspect the road centerline and observe how the Chord Points are placed. These Chord Points will be connected in the next section to build Turn Chords. Save the project. Task 2: Constructing Chords 1. Choose View > Toolbars > Editor to load the Editor Toolbar and start an edit session. In the Editor toolbar, set the task to Create New Feature and make Turn Chords the target. On the Editor toolbar, in the Editor drop-down menu, choose Snapping and set the snapping layer to Chord Point vertices. In the Editor drop-down menu, choose Options and set the Snapping tolerance to 50 map units. 2. To build the first chord, activate the Sketch tool and use the cursor to snap to Chord Point T1, the green crosshair located at MP 0.0. Extend the line to the next red "x" and double-click to terminate the chord. Notice that it will be immediately labeled with zero values. Continue moving up the road, building Chord 2. 3. Hold down the C key to access the Panning tool and move along the road. To speed up this process, use the mouse wheel to zoom in and out. Build each chord in order from T1 to T47. The chords will be numbered to match the Chord Points so build them sequentially. When finished building the chords, turn off the background image and inspect them. 4. The next step is to add a Turn Number and the chord length. Open the Turn Chords table and verify that the FID field contains a continuous series of values that starts with 0 and ends with 47. If the FID values are not in a continuous sequence, renumber the chords to match the Turn Point series. 5. Right-click on the Turn_No field and choose Field Calculator. Use the Field Calculator to number the chords by using the simple formula [FID] + 1 to populate the Turn_No field. Make Continued on page 54 www.esri.com The chords will be numbered to match the Chord Points so build them sequentially. When finished, turn off the background image and inspect the chords. Use the Field Calculator to populate the Turn_No field by numbering the chords using the simple formula [FID] + 1. ArcUser Winter 2010 53