How To: Draw a Cross Section Axes and Topography

Choice of Procedure

There are many different ways in which you could draw your topography and the left, right and bottom bounding lines (here called axes). For example, you could draw a series of separate lines and join them up as required later. For that you would use the Freehand Tool with a click, move and click operation for each line segment, and starting each line on the finishing point of the previous line (this turns out to be very tedious when you need to join the segments later). You could use the Bezier Tool with a click, move, click, move operation until you get to the end of the line. If you have set a Grid to 1mm AND you have set Snap to Grid AND you have zoomed in sufficiently, you should be able to click on the values from your tabel of XY Data. Watch the markers on the ruler, and do not worry if one or more clicks are not in the right place as you can adjust the node positions later.

Axes and Topography

Make sure the Bezier Tool is selected. Make sure that you have zoomed in sufficiently to be able to place each point to the nearest X and Y values to those in your table. Click on the point representing each X and Y value in turn. When you get to the last X and Y value click at the bottom of the right axis (X=Max, Y=0), then at the bottom of the left axis (X=0, Y=0) and finally at the top of the left axis where you started. With a bit of luck your outline can now be filled with a colour as illustrated below:

There are several reasons why the topography might not close at this stage. Continue when you have corrected any problems.

Check Node X and Y values

At this stage you can zoom in to make sure the nodes have the X and Y values in your hand-written table. With a 1mm grid setting and Snap to Grid set you should be able to correct any initial drafting errors fairly easily. Note that you could set a finer grid, say 0.5 or 0.1 mm, or write a script for placing the nodes exactly, but it is doubtful whether the extra precision is really necessary for this exercise.

Smooth the Topography

With the Shape Tool click on the topography to select it. Then select all of the topography nodes by clicking and dragging a box to outline them. Click on the Convert Line to Curves button. Then click on the Make Node Smooth button.

The left axis may appear as a curve too. Select the axis by clicking on the line and then on the Convert Curve to Line button.

At the top of the left axis (possibly the right axis too) it will be necessary to select the node and use the Convert to Cusp button and then drag the lever handle to make the topography meet the axis at an angle. Note that you may wish to switch off Snap to Grid.

Final Topography Adjustments

You may need to make some final adjustments to the topography. You can do this by clicking and dragging the topography line. The illustration below shows a hill having a little more curve added.

Make sure you are satisfied with the topography at this stage. It is bad practice to have to make adjustments after making copies for use on other layers.