Tutorial 11

In this tutorial you will;

¨ Contour a natural surface from a job supplied.

¨ Identify where the model fails to accurately represent a creek through the surface.

¨ Define discontinuity or breakline strings along the creek.

¨ Re-contour the surface to incorporate the discontinuities.

Start Ezicad_Premium in your usual fashion, either from the Start Programs list, or from a shortcut if you have one set up on your desktop.

Selecting the Job

Use the File, Open command to open job Breaklines in your Ezicad_Premium Tutor folder. The screen should appear as below left, and you should maximise the window to fill the screen so you have a display as seen below .

Now pull down the Contour Menu and select Surface Parameters.

For our purposes the majority of the default values will be sufficient, however you should change the Contour interval so you have a Major Interval of 2.0 and a Minor Interval of 0.5.

This will give you a clearer picture of the surface.

Once the changes are made, select OK .

Next you should pull down the Contour Menu and select the Form model option.

The triangles will be quickly formed and the screen should appear as below left.

Now pull down the Contour menu again, and select Calculate Contours, and when asked you should save the contours that have been formed, and appear as in the screen nearby

Now, if you inspect these contours, you will find it difficult to see any creek running across the model, however we can tell you that there should in fact be one.

In fact, the field party has told us that the following points define the creek.

Left Bank - points 11,24,39,59,76

Centreline points 45,25,40,60,77

Right Bank points 46,26,41,61,78

Had they actually coded the points in the field it would have been better, and we could have used the Feature Code functions which you learned in Tutorial 10 to automatically created the lines, but you have to work with what you get, and here no codes were used so we will need to construct the strings manually.

To get a clearer picture of how the model has been formed, Zoom up a window of the approximate size you see in the screen shown far left

Once the screen is redrawn, you should see a set of contours similar to those in the screen close left, and it is obvious that these contours are not representing a creek, so we need to re-educate the model, and this can be easily achieved by inserting discontinuities or breaklines.

(The two names are interchangeable as far as Ezicad is concerned and it depends which school you went to as to which one you are more familiar with and prefer to use)

Since you are satisfied that the existing contours are a little “odd” you should Zoom Extents so you can see the full job while you add in some strings to represent the creek.

Adding Discontinuity Strings

In order for the program to take notice of the discontinuities, they need to be placed in a string folder called “DISCON1” where the “1” signifies that these discontinuities are to apply to Surface 1. (Obviously when you get to use Surface 2, you would use a folder named ‘discon2’)

Pull down the Strings menu, and select the Add option.

When you select Add, a screen will appear as seen below.

Pull down the ‘Folder” name and select ‘discon1’

Now you need to identify the string you are about to enter. Select the field titled “ ID” and type in LB (to signify Left Bank) and press Enter or the Tab key.

The cursor will move into the field at the bottom of the “Strings” window, and here you need to define the points that will be connected in this string.

From the information above, you should type in 11 followed by a comma (,) and then 24 followed by a comma - you will see a line appear on your screen connecting these two points.

Then continue entering the points until your field has the following string in it

11,24,39,59,76

Note, that you may either type in the point numbers, or select them with the cursor if you can see them clearly.

Once you have entered in point 76 you should select the Apply button to save the string away.

Now set the String ID to CL.

The list of Points is 45,25,40,60,77 and then select Apply

You should now see two lines across the display indicating the left bank and the centreline of the creek.

You should now repeat the process with a String ID of RB and points of 46,26,41,61,78. Select Apply to end this string entry.

Then select Finish to close down the Add Strings window.

You should be able to see the strings drawn over the contours, but if you wish to get a clearer picture you can turn the contours OFF by using the Modes screen.

Re-Form The Model

Now that the discontinuities have been inserted, it is time to reform the model to incorporate them.

Pull down the Contour menu and select Form Model.

Note: in normal work, if you have the breakline strings entered before you form the model the first time, they will be automatically taken into account and the triangles formed accordingly

The triangles will form quickly on the screen, and if you pay close attention, once the triangles are completed you will see a small window appear informing you that it is re-organising the triangles to take the discontinuities into effect.

Since this process is fairly speedy, and this is a rather small job, if you have the latest souped up Pentium, you may only see a flash as this happens.

This process needs no intervention from you and once it is completed the screen will show you the triangle model.

Pull down the Contour Menu once more, and this time select Calculate Contours, and save them when the process is finished.

The screen should now appear as seen at left.

It should already be apparent that there is now a creek running through the model.

If you wish to Zoom into the window that you used earlier in this tutorial you should now see the creek clearly defined as seen below.

(And, if you have only done the zoom extents since you had that window on view, you could do a Zoom Previous to get back to it immediately – not sure how? – can I suggest you have a look back at Tutorial 1 where a number of these time saving tools are explained – and if you still don’t want to look at tutorial 1 try pressing Z then P immediately and see what you get.)