DTM Civil 3D Digital Terrain Modeling Tutorials
Digital Terrain Modeling Definition
A Digital Terrain Model (DTM) is a digital file, or a digital representation within a file, providing a detailed representation of topographical variations in the Earth’s surface. In Civil 3D, a DTM is created from a Triangular Irregular Network, or TIN.
A TIN is a vector-based data structure for storing terrain information in a digital terrain model. In a TIN data model, each sample point has an x,y coordinate and a height or z value.
A common mistake is to process a TIN for the creation of a terrain model (a.k.a. a “surface”) without adding breaklines. Breaklines are added manually (or via survey figure or feature line commands) as a means of establishing the path at least two vertices of a triangle must follow. Triangles in TIN will not cross a breakline (thereby establishing a break in grade, e.g. a top, toe, or flow line).
Digital Terrain Modeling Tutorials
- DTM105 Digital Terrain Modeling: Tips, Tricks, and Techniques
Covers everything you need to know about digital terrain modeling. Was written using Civil 3D 2009 but is a good reference for other releases, and generally speaking, the same principles apply. Includes: Terrain Modeling & Delaunay Triangulation, Breaklines, DTM Visulaization Techniques, Terrain Modeling & Vertical Faces, Weeding Factors, Maximum Triangle Length, Corridor modeling, SRTM Surface Data & Google Earth, Importing Contours From an ArcView Shapefile, Setting Up Point Styles, Description Keys & Point Groups, Corridor Modeling: Terminology, Assembling a Complex Corridor Model at an Intersection, Corridor Modeling: Generic Links. 46 Pages - DTM104 Create Surface Data Shortcut
In order to share data (surfaces, alignments, etc.), it’s necessary to create “data shortcuts.” Surface data shortcuts are the subject of this tutorial. - DTM103 Turn Off Contours
This video shows you how to turn off (or off course on) once a surface has been created. - DTM102 Create a Surface from Contours (Polylines)
The video “Import TNRIS StratMap Shapefile” noted above showed you how to import a shapefile with contours (essentially, they are polylines with elevation). This video walks through the process of creating a surface in Civil 3D using these polylines. - DTM101 Create Surface from Unknown Survey Source
It’s common to receive a survey from an unknown source with various types of data included. This tutorial shows you how to study the data, and then how to use the data to build a Civil 3D surface. - DTM100 Creating a Surface Using Points.
Surface creation in Civil 3D is relatively straight forward. This video shows you one simple method using points.
Related Tutorials
- MAP101 Import TNRIS StratMap Shapefile
The Texas Natural Resource Information System (TNRIS) makes available ArcView shapefiles of the contours derived from the original USGS QUADs. These shapefiles can be imported to MAP 3D, or AutoCAD® Civil 3D®, and used to build a terrain model. Regardless of the type of shapefile you have (contours, roads, etc.), the process is essentially the same.
Digital Terrain Modeling Links
Civil 3D Tutorials
AutoCAD® Civil 3D® Tutorials
Videos & Podcasts require QuickTime®.
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