**3.1 Digital terrain model**

Digital Terrain Modeling (DTM) is a concept that underlies all calculations in Civil Engineering involving elevation or slope - profiles, cross sections, grading and volume calculations.

The process of DTM involves the creation of a data structure that the software can instantly "touch" to retrieve elevations or slopes, representing either existing or proposed conditions.

DTM mathematically completes all interpolation possible between the data supplied, and stores the result in a digital file for easy retrieval.

Surfaces can certainly be produced from other data types, including point data.

There are certain data types that are universally applicable to any DTM effort in Civil Engineering and Surveying. These data types are constant in any program: Civil 3D, Open Roads Designer, ArcGIS, etc.

The three data types which can be used in constructing a DTM are Point Data, Breakline Data, and Contour Data.


Most Civil Engineering and Surveying applications will utilize some combination of data types in a Terrain Model; having two types present is common and all three is not unusual at all.

Triangular irregular networks (TIN) are a representation of a continuous surface consisting entirely of triangular facets, used mainly as Discrete Global Grid in primary elevation modeling.

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**Figure 2.**

*Digital terrain model.*

*BIM Approach for Smart Infrastructure Design and Maintenance Operations*

TINs can be constructed using three types of vector information: altitude measurements (mass points), surface continuity breaklines, surface continuity break

The points contain the X, Y coordinates and the Z value. All points are used to establish a connection with the two closest points to create triangles. Surface triangulation is based on the Delaunay algorithm, which ensures that no points are

The Discontinuity Lines represent the characteristics of a linear infrastructure

Contours are the characteristics to define bounded 3D surfaces. Surface contours

**Figure 2** shows the triangles that result from Digital Terrain Modeling where the elevation value is retrieved from the digital surface and displays it in the Tooltip,

Creating and defining a horizontal alignment is one of the first steps in infra-

You can draw the alignment geometry as a polyline, and then create the named alignment from that geometry. For greater control, you can create an alignment

Create alignments in many ways, such as creating them from polylines, from

• Fixed elements have its position totally defined by specifying a combination of start/end points or center, length, bearing or angle, and radius. However, as the fixed position of a computator is defined by points that are dependent (referenced) on other elements, a fixed computator is actually free to move as the referenced elements move. It is "fixed" in respect of its location to the

The alignment can be created using fixed, floating, and free elements:

In **Figure 3** a workflow to design and edit alignments is shown.

object or You can also make edits to alignments using grips.

such as curbs, retaining walls, etc. These lines also define the edges of the triangles. Breaklines can be created from linear entities such as line, polyline,

surface improves the performance of a TIN Surface plane.

can be created with closed polylines. Defining external contours on a large 3D

*DOI: http://dx.doi.org/10.5772/intechopen.94242*

polygons (polygon surfaces).

within the circle of a triangle.

instantly, and anywhere on the surface.

pipe networks, and from LandXML data.

referenced element;

**3.2 Horizontal-vertical alignment**

arc, circle.

structure design.

*BIM Approach for Smart Infrastructure Design and Maintenance Operations DOI: http://dx.doi.org/10.5772/intechopen.94242*

TINs can be constructed using three types of vector information: altitude measurements (mass points), surface continuity breaklines, surface continuity break polygons (polygon surfaces).

The points contain the X, Y coordinates and the Z value. All points are used to establish a connection with the two closest points to create triangles. Surface triangulation is based on the Delaunay algorithm, which ensures that no points are within the circle of a triangle.

The Discontinuity Lines represent the characteristics of a linear infrastructure such as curbs, retaining walls, etc. These lines also define the edges of the triangles. Breaklines can be created from linear entities such as line, polyline, arc, circle.

Contours are the characteristics to define bounded 3D surfaces. Surface contours can be created with closed polylines. Defining external contours on a large 3D surface improves the performance of a TIN Surface plane.

**Figure 2** shows the triangles that result from Digital Terrain Modeling where the elevation value is retrieved from the digital surface and displays it in the Tooltip, instantly, and anywhere on the surface.
