Tutorial 6 - DTM Basics

This exercise will teach you all the basic functions you need to know in order to create a digital terrain model (DTM).

You will complete the following tasks:

If you haven't done so yet, read the Before You Start section before proceeding.

If you get lost or stuck while you are doing this tutorial, do the following:

The intention is that you use our Tutor data whilst working though this tutorial. You will find the data in the following folder:

C:\Users\Public\Public Documents\Knowledge Base Software\Examples\Tutor

Open an Existing Drawing or Create a New One

Civil Designer’s projects are based on the active drawing file and therefore may contain any drawing entities as well as references to external files (Xrefs).

In this example, you are going to use File ► Open to load a cadastral drawing, which will form a backdrop to the rest of the design data.

  1. Navigate to the Examples directory as shown below and open the Tutor Cadastral.dr4 drawing file.

  2. If you do not have an existing drawing to use as a backdrop, simply create a new drawing using File ► New.

Create a New Project

The first task is to create a new project file.

  1. Switch into Survey mode by clicking the Survey icon on the Applications toolbar, or selecting Applications ► Survey. The menu and toolbars are updated to contain design functions pertinent to this design mode.

  1. Select File ► Project Settings to display the Project Settings.

 

All the available items remain greyed-out until a checkbox next to one of the design modules is clicked.

  1. For the purposes of this tutorial, you will be using a Terrain file so click on the checkbox next to Terrain. The ... button for Terrain on the right side of the window becomes active. Click ... to create a terrain file.

  2. The file browser displays.

  1. Navigate to a suitable subdirectory for storing data, type in the file name Tutor and then click Open.

  2. If the file does not yet exist, you are asked if you want to create it.

Click Yes and you are returned to the project settings.

If a file of that name already exists it would be used without change. In your case, you require any empty file to work with, so either use a filename other than Tutor, or navigate to an alternative subdirectory that does not contain an existing file of that name.

  1. Fill in the rest of the data as shown below.

Note that the path for your Terrain file will most likely differ from that displayed here.

  1. Click OK to create the project.

Import ASCII Data

  1. Once the project has been created, switch into Survey mode by clicking Survey on the Application toolbar, or select the Survey option from the Applications menu.

  2. Now select File ► Import ► ASCII YXZ ► Single File.

  3. You can import data from a fixed column, or comma delimited, ASCII file. Use the standard file browser to navigate to the Examples directory.

  1. Select the _Tutor.dat. file.

  1. The following Import ASCII options display.

  1. Set the options as illustrated, and then click Next.

  1. An extract of the first 25 lines of the ASCII file is shown, from which you must now specify the sequence of data items. In this case, you have the point name, Y, X and Z values.

  1. To set the field type for a column, click on the relevant column header and select the field type from the pop-up menu that displays.

  1. Set the column headers as shown, and then click Finish to start the import.

  2. The following Confirmation message displays.

  1. Click Yes to proceed.

  2. You must now specify the destination surface for the incoming data. The Destination Surface Selection options display.

  1. The left-hand column (Found) indicates Surface None (or 0), 1, 2 and so on. For each of these surfaces, you can allocate a corresponding destination surface. In this case, you want all the points to be in Surface 1.

  2. Click OK and the data is imported. The site is redrawn to display all the imported points.

  3. Save your data using File ► Save.

Generate a Digital Terrain Model

Civil Designer has very powerful functions to create and edit a digital terrain model from survey data.

There are two methods to construct the Digital Ground Model (DGM). The first is by means of triangulation, which connects all the points into a triangular irregular network (TIN). This method is extremely fast and works very well on uniform sites with no distinguishing features.

Let's examine the results so far.

  1. Change to Terrain mode by clicking on the Terrain icon in the Applications toolbar.

  2. Select the Model ► Triangulate ► In Memory.

  1. The Triangulation Settings display.

  1. Set the values as indicated, and then click OK to proceed.

  2. The site is triangulated. After the triangulation is completed, the following information displays.

  1. Click OK to continue. The triangulated site displays.

Display Settings

The Display Settings allow you to change the way the DTM is displayed on screen. The options on the Display toolbar switch the various option on/off.

  1. To view the generated lines, select Settings ► Lines or click the Lines icon in the Display toolbar. The lines are displayed.

  1. You can now activate various options that make the editing of the lines easier and more intuitive.

  2. The first is to display the site contours by selecting Settings ► Contours, or clicking the Contours icon in the Display toolbar.

  1. In order to understand the site better, you can also activate the point name display by selecting Settings ► Names or clicking the Name icon in the toolbar. You can activate the point height display by selecting Settings ► Heights, or clicking the Heights icon in the toolbar.

  1. Zoom in on the top quarter of the site by selecting View ► Zoom Window, or pressing [Z] and [W].

  2. Define a fairly small area so you can display some detail, as illustrated below. In this case, only line display is switched on.

  1. Now toggle the name and height display options to show the following.

Editing Lines

The contours are derived from the lines that indicate areas of linear interpolation between two elevations. As you change the lines the contours are updated.

Switch on the contour display by selecting Settings ► Contours, or by clicking the Contour icon in the Display toolbar.

Zoom and/or Pan

Civil Designer has very powerful panning functions. To pan to the current cursor position simply press [W]. To zoom in press [M]; and to zoom out press[D]. Alternatively, position the cursor at the point you want to zoom in or out and then roll the mouse wheel.

Editing the DTM

In order to define a terrain model correctly, it is essential that the break lines or changes in grade be defined correctly.

  1. Change to the Terrain Lines toolbar.

This toolbar contains functions to edit the digital terrain model by changing the break lines.

  1. You can remove a line by selecting Model ► Delete Break Line, or by clicking the Delete Breakline icon on the Terrain toolbar. Notice how the contours are updated after each change to the line model.

  2. Now add a line by selecting Model ► Add Break Line option; or by clicking the Add Breakline icon on the Terrain toolbar.

These editing functions allow you to tweak the terrain model until the contours accurately represent the topography of the site. Press [Esc] to terminate these functions.

One alternative is to correct the model by means of manual editing using the add- and delete line functions but, on a large site, manual editing can become very tedious.

Intelligent Break Lines

Civil Designer solves this problem with its Intelli-Lines in the Model ► Intelli-Lines option.

  1. First switch off the point names and heights display (if switched on), and zoom the entire site using View ► Zoom All or [Z]+[A].

  2. Now run the Model ► Intelli-Lines option with the following settings.

  1. Click OK to proceed. The lines are regenerated but only connect the points labelled as ER, as shown in the next illustration.

 

Note that if you chose to retain the existing lines for these operations, you would be adding lines on to the existing model. Note also that you chose to generate these lines as feature lines. This means that you will not inadvertently delete these lines when you next use the Intelli-Line option; and you choose to delete existing lines, or when we triangulate the model.

  1. Change to the Terrain Lines toolbar and tidy up the feature lines by using the various view options and the add- and delete feature line functions. Don't worry about any other points at this stage.

  1. You should now have an accurate digital terrain model that forms the basis of the rest of your design. Note how the road edges remain clearly defined in the illustration below:

  1. An alternative to the above procedure is to use the Model ► IntelliLines option again, instead of triangulation and selecting to keep existing break lines at all times.

This would allow you to control the break line generation by specifying point names and distances to process, in order to build up the model. This is, however, only desirable in very complicated models.

Display a Backdrop Drawing

Civil Designer allows you to load a drawing into the current project, which will be displayed as a backdrop to the terrain data i.e. a drawing of the cadastral layout of a town.

Before starting this section, switch off all line, contour, name and height displays. This will give you a clean view with which to work.

  1. In order to specify the drawing to be loaded, select File ► Project Settings from the menu.

  2. Set up the project as follows.

  1. Click ... next to XRef Drawing and navigate to the example data directory. Now select the file Tutor.dr4 file.

 

  1. Once the drawing is selected, click OK to activate the changes.

  2. The reference drawing is loaded and displayed along with the terrain data.

Generate Contours

Even though you can display the contours during the editing process, they need to be generated and saved if you want to include contour labels.

  1. Zoom to the entire site and then select Terrain ► Generate Contours.

  2. Specify the following settings.

  1. The contours are generated and saved to disk for plotting.

Create a Site Plan

Now you can reap the fruits of your labour by producing a site plan that includes contours with height labels.

Firstly, you need to set up your display correctly as the site plot is generated mostly from what you can see on the screen.

  1.  Select Settings ► Display Settings or click the Display Settings icon on the Display toolbar.

  1. The following display settings options display. If required, click the Terrain item to display the correct set of pages.

  1. Make sure the Display Settings are as shown, and that the draft text option is off.

  1. Now click on the Contours item to specify the type of contours to display.

You may also select to highlight the contours at some multiple of the general contour interval; and to specify the pens to be used for contours and for highlighted contours (if selected).

  1. Click OK and the site is redrawn to show the selected items.

  1. Now select Plot ► Generate.

  2. The following Plot Setup options display.

  1. Click ... and the file browser displays.

  1. Navigate to the Examples\SheetFiles subdirectory and select the sheet called Plan.sht.

  1. Now set the sheet size to A0, as shown below.

  1. Click Next and the Plan Setup options display.

  1. Configure the settings as shown above, and then click Add to define the plot area.

  2. You are prompted to:

Plan Plotting: Indicate plot centre (Right-click to end)

  1. The project displays with a rectangle attached to the cursor, indicating the region that can be included at the specified sheet size and scale.

  1. Click at the position where the centre of the plot should be located.

  2. You are asked:

Click No to plot the plan without any rotation; or Yes to rotate the plot window.

  1. Right-click and select Quit from the popup menu.

  2. The Plan Setup displays with the centre coordinates and angle of rotation of the defined plan.

As you can see, the position of your plan has now been defined, and the Yes option in the Plot column specifies that this particular plan must be generated.

This allows us to generate a plot at exactly the same position and rotation at some future stage.

  1. Click Next to display the Plan Lists options.

These options allow you to specify what additional data must be included on the plan, as well as the position of these detail lists.

  1. Set the options as shown above, and then click Finish.

  2. A drawing similar to the following drawing layout is generated.

  1. Use the program functions to zoom in, pan, etc. If you want to print or plot the drawing, select layout to be printed and then select File ► Print. Remember to check the paper size before you print.

Saving Your Project

Close the drawing window and then save the project by selecting File ► Save. This saves the master drawing as well as the design data associated with the project.

This project is used in all the following tutorials, so it is important that you retain the current information for the next tutorial.

You have now completed Tutorial 6.

You can: