=== Organizing the Propagation Scene by Block Groups ===
In EM.Terrano, all the geometric objects associated with the various scene elements like buildings, terrain objects surfaces and base location points are grouped together as blocks based on their common type. All the objects listed under a particular group in the navigation tree share the same color, texture and material properties. Once a new block group has been created in the navigation tree, it becomes the "Active" group of the project workspace, which is always displayed in bold letters. You can start drawing draw new objects under the active node. Any block group can be made active by right-clicking on its name in the navigation tree and selecting the '''Activate''' item of the contextual menu.
It is recommended that you first create block groups, and then draw new objects under the active block group. However, if you start a new EM.Terrano project from scratch, and start drawing a new object without having previously defined any block groups, a new default impenetrable surface group is created and added to the navigation tree to hold your new CAD object. You can always change the properties of a block group later by accessing its property dialog from the contextual menu. You can also delete a block group with all of its objects at any time. {{Note|You can only import external CAD models (STEP, IGES, STL, DEM, etc.) only to the CubeCAD module. You can then transfer the imported objects from CubeCAD to EM.Terrano.}}
[[Image:PROP15.png|thumb|400px|EM.Terrano's Domain Settings dialog.]]
[[Image:PROP4.png|thumb|400px|EM.Terrano's Global Ground Settings dialog.]]
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[[Image:prop_manual-12_tn.png|thumb|500px|An imported external terrain model.]]
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[[Image:Info_icon.png|40px]] Click here to learn more about all the different '''[[Block Types]]''' in EM.Terrano.
[[Image:Info_icon.png|40px]] Click here to learn more about '''[[Defining_Materials_in_EM.Cube#Moving_Objects_among_Material_Groups | Moving Objects among Block Groups]]'''.
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{{Note|Except for external terrain models, you can import other external objects (STEP, IGES, STL, etc.) only to '''[[CubeCAD]]'''. From [[CubeCAD]], you can then move the imported objects to EM.Terrano.}}
[[Image:Info_icon.png|40px]] Click here for a general discussion of '''[[Defining Materials in EM.Cube]]'''.
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=== Defining Base Point Sets ===
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[[File:PROP1.png|thumb|300px|[[Propagation Module]]'s Base Set dialog]]
EM.Terrano uses '''Point''' objects to position transmitters and receiver in the propagation scene. Points are regular CAD objects that can be moved around (translated) in the project workspace. The point objects that are used to represent the transmitters and receivers are grouped together and organized as '''Base Sets''' in the "Physical Structure" section of the navigation tree. When you move the point objects or change their coordinates, all of their associated transmitters or receivers immediately follow them to the new location. For example, you can define a grid of receivers using a base set that is made up of a uniformly spaced array of points and spread them in your scene. You can easily interchange the role of transmitters and receivers in a scene by switching their associated bases. The usefulness of concept of base sets will become apparent later when we discuss placement of transmitters or receivers on an irregular terrain and adjustment of their elevation.
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To create a new base set, follow these steps;
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* Right-click on the '''Base Sets''' item of navigation tree and select '''Insert Base Set...''' A dialog for setting up the Base Set properties opens up.
* Enter a name for the base set and change the default blue color if you wish. It is useful to differentiate the base sets associated with transmitters and receivers by their color.
* Click the {{key|OK}} button to close the Base Set Dialog.
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Once a base set node has been added to the navigation tree, it becomes the active node for drawing new objects. Under base sets, you can only draw point objects. All other object creation tools are disabled. A point is initially drawn on the XY plane. Make sure to change the Z-coordinate of your point, otherwise, your radiator will fall on the global ground at z = 0. You can also create arrays of base points under the same base set. This is particularly useful for setting up receiver grids to compute coverage maps. Simply select a point object and click the '''Array Tool''' of '''Tools Toolbar''' or use the keyboard shortcut "A". Enter values for the X, Y or Z spacing as well as the number of elements along these three directions in the Array Dialog. In most propagation scenes you are interested in 2D horizontal arrays along a fixed Z coordinate (parallel to the XY plane).
== EM.Terrano's Ray Domain & Global Ground ==