EM.Terrano Tutorial Lesson 6: Modeling Irregular Terrain

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Tutorial Project: Modeling Irregular Terrain
Terrano L6N Fig title.png

Objective: In this project, you will construct an irregular terrain surface to serve as the ground of your propagation scene.

Concepts/Features:

  • Wizard
  • Terrain Surface
  • Impenetrable Surface
  • Transmitter Set
  • Receiver Set
  • Terrain Elevation
  • Received Power Coverage Map
  • Random Rough Surface
  • Roughness Statistics

Minimum Version Required: All versions

'Download2x.png Download Link: EMTerrano_Lesson6

What You Will Learn

In this tutorial you will use a wizard to create a plateau terrain profile. You will learn the special properties of terrain objects affecting the elevation of objects above them.

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Getting Started

Open the EM.Cube application and switch to EM.Terrano. Start a new project with the following attributes:

Starting Parameters
Name EMTerrano_Lesson6
Length Units Meters
Frequency Unit GHz
Center Frequency 1 GHz
Bandwidth 1 GHz

Creating the Plateau Terrain Profile

For this tutorial lesson, you will use a wizard to create a large terrain profile in the project workspace. Click on the Plateau Terrain Wizard PlateauTerrainWizardIcon.png button of the Wizard Toolbar or select the menu item Tools → Propagation Wizards → Plateau Terrain. A large plateau terrain object appears with a random rough surface.

EM.Terrano's wizard toolbar.
The geometry of the default plateau terrain created by the wizard.

Just like impenetrable and penetrable surfaces, a terrain surface is a special type of object in EM.Terrano that is used to model non-flat or irregular ground. Terrain objects are grouped together under Terrain Surfaces node of "Physical Structure" in the navigation tree. Open the variables dialog and see all the variables defined by the wizard for the plateau terrain scene. Edit and change the definition of the following variables:

Variable Name Original Definition New Definition
area_size 400 800
slope 0.5 0.25
The variables dialog showing the new parameters of the plateau terrain scene.
The geometry of the plateau terrain after changing some of its parameters.

Constructing Blocks of Buildings

Create a default impenetrable surface group in the navigation tree with brick composition. Then, under "Block_1" draw two box objects withe following parameters:

Object Geometry Block Group Surface Type Material Dimensions Location Coordinates Rotation Angles
Box_1 Box Block_1 Impenetrable surface Brick 80m × 40m × 20m (320m, 2400m, 0) (0°, 0°, 0°)
Box_2 Box Block_1 Impenetrable surface Brick 40m × 80m × 20m (-300m, -300m, 0) (0°, 0°, 0°)

In Tutorial Lesson 1 you learned how to create an array of point objects. In this lesson, you build an array of box objects to model a block of buildings. Select Box_2 and click the Array Array tool tn.png button of the Tools Toolbar, or simply use the keyboard shortcut A. The Array Dialog opens up. Enter 3, 2 and 1 for the Element Count along the X, Y and Z directions, respectively. Enter 100m, 120m and 0 for Spacing along the three axes, respectively. The table below summarizes the array properties:

Array Object Parent Object X Count Y Count Z Count X Spacing Y Spacing Z Spacing
Box_2_Array_1 Box_1 3 2 1 100m 120m 0
The property dialog of the box array object.

At this point, your physical scene should look like the figure below:

The geometry of the plateau terrain with a set of buildings at their original positions.

The most important property of terrain objects in EM.Terrano is that they can (optionally) affect the elevation of objects placed on them. Otherwise, from a modeling point of view, terrain objects behave like impenetrable surface. Open the property dialog of the Impenetrable Surface group "Block_1", and check the box labeled Adjust Blocks to Terrain Elevation.

The property dialog of the impenetrable surface block group.

As soon as you close the impenetrable surface block's property dialog, you will notice that the building objects are lifted up and placed on the surface of the terrain.

The geometry of the plateau terrain with a set of buildings after adjusting their elevations.

It is worth examining the mesh of your scene at this time. A terrain surface is a tessellated surface object, which consists of a large number of triangular cells. View the mesh of your physical structure to get a sense of its geometrical complexity.

The facet mesh of the plateau terrain with a set of buildings.

Defining the Transmitter & Receivers

For this tutorial lesson, use the Basic Link Wizard to create a vertically polarized half-wave dipole transmitter and a grid of isotropic receivers. Set the Grid Extents equal to 800m, and keep the default values of the other parameters, i.e., a transmitter height of 10m, receiver height of 1.5m and receiver spacing of 5m. The transmitter base location point called "TXP" is originally positioned at (0, 0, 10m). Change its coordinates to (100m, 100m, 10m). At this time the transmitter is hidden under the terrain, and so are a large number of receivers.

The plateau propagation scene with the transmitter and receivers at their original locations.

Similar to building blocks, a terrain surface can also (optionally) affect the elevation of the transmitters and receivers that are placed above it. Open the property dialogs of the transmitter and receiver sets and check the boxes labeled Adjust Tx Set to Terrain Elevation and Adjust Rx Set to Terrain Elevation, respectively. In the case of the receiver set, also check the box labeled Display Small Rx Points at the bottom of the dialog.

Adjusting transmitters to terrain elevation in the transmitter set dialog.
Adjusting receivers to terrain elevation in the receiver set dialog.

At this time, your project workspace must show a scene like the figure below.

The propagation scene with the transmitter and receivers adjusted to the terrain elevation.
Attention icon.png The Z-coordinate of a transmitter or a receiver located above a terrain surface is adjusted to the sum of its original height and the terrain elevation at its base location.

To get a better view of the relative position of the tranmsitter and receivers and their corresponding base location points, click the Right View View-right tn.png button of the View Toolbar to see a side view of your propagation scene.

The (2D) right view of the propagation plateau scene.

Running an SBR Analysis of the Propagation Scene with the Plateau Terrain

Run a single-frequency SBR simulation of your plateau terrain scene and visualize its received power coverage map. You can see from the figure below that the upper portion of the plateau obstructs many direct rays from reaching the valley region. As a result, the reception around the building array is not good.

The received power coverage map of the plateau terrain scene with the transmitter base at X = Y = 100m and Z = 10m.

To improve the reception, you can bring the transmitter to the edge of the plateau. Keep in mind that to move a transmitter or receiver, you need to move their associated based point sets. Change the coordinates of the base point "TXP" to X = Y = 30mm. Keep the original Z-coordinate of 10m. Now run a new SBR analysis of the scene and visualize its coverage map. You will see that the valley region now gets considerable reception.

The received power coverage map of the plateau terrain scene with the transmitter base at X = Y = 30m and Z = 10m.

The coverage can be further improved by raising the height of the transmitter above the terrain surface. Remember that the height of the transmitter was parameterized by the basic link wizard. Open the variables dialog and change the value of "Tx_h" to 20m.

Changing the transmitter height from variables dialog.

Run a new SBR simulation. Visualize the received power coverage map and see the improvement in reception due to the increased height of the transmitter.

The received power coverage map of the plateau terrain scene with the transmitter base at X = Y = 30m and Z = 20m.

Changing the Terrain's Surface Roughness Statistics

Among the variables that the wizard initiated are root-mean-square (RMS) height and correlation length of the rough surface. The terrain surface object is assumed to have an additional offset elevation that is represented by the variable called "elevation". Open the variables dialog and change the definition of the following parameters:

Variable Name Original Definition New Definition
elevation 0.5 2
rms_height 0.5 1.0
correl_len 10 5
The variables dialog showing the new statistical parameters of the plateau terrain scene.

As you can see from the following figure, the new roughness statistics make the terrain more rugged than before.

The geometry of the plateau terrain after changing its surface roughness statistics with receivers hidden.

Run an SBR analysis of the new rugged terrain scene. Note that this is a relatively large computational problem. The simulation output window reports some of the simulation parameters:

SBR Simulation Parameter Value
Total Number of Facets 62,066
Total Number of Edges 39,680
Total Number of Receivers 25,921
Total Number of Transmitted Rays 64,980

At the end of the SBR simulation, visualize the coverage map. Note how the rugged terrain surface has caused significant wave diffusion throughout the scene.

The received power coverage map of the plateau terrain scene after changing its surface roughness statistics.



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