Urban design - surfaces

urbn-dsn-srfc-01.mp4 5:51

There are two methods for creating the refinement surfaces. The conventional method is what is thoroughly documented in the WisDOT Civil 3D training curriculum. We are going to utilize an alternative surface progression for our urban project. The purpose of the alternative progression is to make surface refinements around the driveway aprons simpler.

Conventional surface progression

The conventional Crdr-Datum surface extends to the slope intercept. The conventional Crdr-Top surface extends only to a point roughly 2 ft behind the back of curb and gutter (typically the ETW_Datum_CG feature line). Since the driveway aprons span the ETW_Datum_CG feature line, any refinements made to them would need to happen in both the Rfnt-Datum and Rfnt-Top surfaces.

Alternative surface progression

In the alternative progression, the Crdr-Datum surface only extends to the edge of the roadway subgrade (typically 2 ft outside the back of curb and gutter). The Crdr-Top surface extends to the slope intercepts. This makes it possible to refine the driveway aprons in the Rfnt-Top surface alone. These refinements then automatically appear in the Rfnt-Datum surface.

urbn-dsn-srfc-02.mp4 4:46

urbn-dsn-srfc-03.mp4 4:34

In most cases some surface refinements will be needed for the urban driveways in the Rfnt-Top surface. This will require the addition of some breaklines and the deletion of some surface points.

Determine driveway breakline needs

This surface refinement workflow is based on a particular driveway construction detail. The workflow could vary slightly for other variations of driveway design.

The purpose of Steps 6 and 7 may not be apparent, but they are necessary. These steps are important for the Refinement-Datum Surface and for the breakline extraction process.

urbn-dsn-srfc-04.mp4 4:46

The Refinement-Datum surface becomes simpler due to the work done with the Refinement-Top surface. To create the Refinment-Datum Surface, first past the Refinement-Top surface into the surface definition. Then, past the Corridor-Datum surface into the surface definition. A clean break should appear along the ETW_Datum-CG feature line location.