From the course: AutoCAD Civil 3D: Designing Gravity Pipe Systems

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Creating a composite surface

Creating a composite surface

- [Voiceover] Before you begin designing pipe networks, one thing you'll want to do is create a single surface that represents the existing and proposed elevations in your project. We're calling this a composite surface, and this is how it's created. First of all, let's talk about why this surface is important. We're about to create a pipe network along this purple polyline, and, for a portion of the length of this design, we're following the proposed elevations represented by the road. But then we branch off here to the left, and we're running through the existing ground elevations. This is an area where the ground hasn't been disturbed. Now usually, these are two separate surfaces in your Civil 3D drawing, one representing existing ground, and one representing finished, and the reason they're separate is because they're derived through completely different means. The existing ground surface comes from a survey of the area, and the finished ground comes from your idea of what the…

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