Import points and generate a digital terrain model in a CAD file

Although what interests us at the end of an exercise like this is to generate cross sections along a line axis, calculate cut volumes, embankment, or the same profiles, we will see in this section the generation of the digital terrain model from the moment to import the points, so that it can be replicated by another user. Because AutoCAD commands are more popular in English, we will mention them in English.

The present exercise will be done using CivilCAD. If you do not have it, in the end we show you how to download it.

If you want to develop this exercise step by step, you can use the sample file called Sts.txt, Which at the end of the article can indicate how to obtain.

  1. The format of the points

CivilCAD can import coordinates in point format from different nomenclature, in this case we will use data from a survey that has been generated in a txt file, where the points are separated by columns, in the following format: Point number, X coordinate, Y coordinate, Elevation and detail.

  • 1 1718 1655897.899 293.47
  • 2 1458 1655903.146 291.81
  • 3 213 1655908.782 294.19
  • 4 469 1655898.508 295.85 CERCO
  • 5 6998 1655900.653 296.2 CERCO
  1. Import points

This is done with: CivilCAD> Points> Land> Import

In the panel that is shown, we choose the option NXYZ, Since we are interested in importing the descriptions, we chose the Annotate description option.

Select accept with the button OK And we chose the file, which in this case is called «Sts.txt«. The process starts importing points and after a few seconds, a message should appear at the bottom indicating how many points have been imported. In this case you should indicate that you imported 778 points.

In order to see the points, an Extent type Zoom is required. Well with the respective icon or on the keyboard using Z> enter> X> enter.

The size of the points depends on the configuration you have, to change this is done with Format> Point Style, Or by using the command Ddptype.

If you want to see them in the size shown in the image, use the indicated point type and a size of 1.5 absolute units.

As you can see, all the points were imported, and the description was written next to the ones that had it.

Also see that some levels have been created according to the imported data:

  • CVL_PUNTO Contains the points
  • CVL_PUNTO_NUM Contains description
  • CVL_RAD Would contain point data from a radial survey.

The color of the levels can be modified as well as the color of the points by turning them from yellow to ByLayer, so that they acquire the color of the layer and are easier to visualize.

If you have the AutoCAD screen in white, you can change it to black using Tools> Options> Display> Colors ... In a dark background color it will be easier to visualize objects in light colors like yellow.

  1. Generate triangulation

Now we need to convert the points we import into a digital terrain model. For this, we must turn off the layers that we do not need.

This is done using the routine:

CivilCAD> Layers> Leave on. Then we touch a point and we do Enter. With this, only the dot layer should remain visible. Also for the next step it is necessary to have all points visible.

To generate the triangulation we do:

CivilCAD> Altimetry> Triangulation> Terrain. The bottom panel asks us if we want to make them based on existing points or contour lines already drawn on the map. Since what we have are points, we write the letter PThen we do Enter. We select all the objects and at the bottom you should tell us that there are 778 points selected.

We do again Enter, and the system asks us how far we will use for the triangulation at the perimeter points. In this case we will use 20 meters, Considering that the survey was done with a grid of approximately 10 meters.

We wrote 20Then we do Enter.

We indicate as minimum angle 1 Degree we do Enter And this must be the result:

A layer named CVL_TRI has been created that contains the generated 3D faces.

  1. Generate Level Curves

One of the most important aspects of digital model visualization is generating level curves. This is done with: CivilCAD> Altimetry> Level Curves> terrain

Here we indicate that the secondary curves (called in thin CivilCAD) are at each 0.5 meters and the main ones (thick) at each 2.5 meters.

And for the curves to soften at the vertices we will use an 4.4 factor and the result should be the image shown below.

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