In this tutorial you will learn how to edit the various properties of the terrain in your designs. This tutorial assumes you have completed and understood Tutorials 1. If you have not, it is highly recommended you do so before starting this tutorial. At the end of this tutorial you will be able to:

When you create a new design, there will only be a single ground tile measuring 100m across. Your design may need to span a larger area than a single tile. To expand the terrain area, left-click on the outlined "plus" squares adjacent to an existing ground tile.

## Height Specification Points

For many designs the terrain topography is not completely flat, but has varying heights and gradients. You will need to model this to get accurate conductor sag and ground clearance. One of the ways you can set the terrain topography is using height specification points. You can place height specification points on the ground using the Terrain Tool  To see how this tool works, follow the following steps:

1. select the tool and left-click somewhere on the ground,
2. this will place a height spec point on the ground where you clicked, it will look like a blue circle,
3. as you move your cursor you will notice another height spec point under the cursor, joined to the first by a blue line,
4. you can place down multiple height spec points in this way, using left-click, each will be joined to the previous by a blue line,
5. right-click will finalise the set of height-spec points that you have placed,
6. you should see something like this:

Each of the height spec points has an associated height that can be edited. To edit the height of a height spec point, select it using the Move and Select Tool, and in the top of the right hand menu you should see the properties of the selected height spec point. Here you can edit its height, as well as its X and Y position. This will look something like this:

As you edit the heights of the height spec points, you will notice the terrain changes shape to reflect the new topography.

### Height Interpolation

One very important thing to note is the interpolation of the terrain between height spec points. The terrain is exactly linearly interpolated between joined height spec points, along the blue lines. Elsewhere, the terrain is approximately interpolated based on the distance to nearby height spec points. This arrangement is targeted at the use case where you may have survey height data along a particular 1-dimensional slice of the terrain. In this case you will know the height and slope of the terrain along the given slice, which you can model using height spec points, but not elsewhere. The below image shows an example of a terrain topography generated from a few height spec points:

### Editing Height Spec Points

Once you have placed down height spec points on the ground, you can afterwards move and delete them. To move an existing height spec points, use the Terrain Tool and left-click-drag on the target height spec point. Drag the point to the target new position, and release.
To delete a height spec point, select it with the Move and Select tool, and press the Delete key. It should be noted that deleting a particular height spec point may also remove joined points as well. A height spec point is automatically removed if it is not joined to any other height spec points. So for example, if you have a series of 3 height spec points, and you delete the middle one, the other two will also be removed.

### Extending Height Spec Point Segments

Once you have placed down a series of height spec points, you may want to extend them. Or you may way to construct a T-junction type arrangement of height spec points and segments (this will depend on your surveyed ground height slices). To do this, use the Terrain Tool, and left click on an existing height spec point. You will not be able to place new height spec points, attached to this point. This works in a similar way to the Conductor Tool. Below is an example terrain topography that you can construct using a t-junction of height spec segments:

In addition to being able to place the height specification points manually, you can also specify the elevation layout of the terrain by importing the data from a DXF CAD file. There are two modes of elevation data that can be imported:
1. profile height data - a single polyline in the XY plane, with the X dimension specifying the distance along the elevation slice, and the Y dimension specifying the height of the terrain at that point on the slice.
2. 3D strips of elevation data - multiple polylines in XYZ space, with the Z dimension specifying the height of the terrain at the XY point on the terrain.

To import elevation data from a CAD file, bring up the import dialog by selecting File > Import Elevation in the top menu bar. This will bring up an import popup, shown below.

In this popup dialog you need to select the file that you want to import the data from, enter the name of the layer containing the elevation data (eg: "groundline"), and select whether you are importing profile height data or 3D height data. Once you have done this, click the Apply button at the bottom.

This completes this tutorial. We really value your feedback, queries, suggestions, send them all our way!