Network Simulation
1. Learning Example
You have 3 points and you use one tracker to observe these 3 points. So place randomly
in the plane view, one instrument and 3 points.
Enter the following coordinates (and do not panic when you see them disappearing!):
Station1
1
1
1.5
Point1
6
1
0
Point2
10
4
2
Point3
1
4
0
In the menu, go to “Options”, “Properties”, in the tab “Display” choose “Set reasonable
boundary”. Now using the “triplet” tool, you can draw your tracker observations.
Question 1: What are “reasonable” choices for the standard deviation on your
observations?
Double click on each triplet and enter your choice of standard deviation. Verify your
entries in the top split window. Run the simulation.
Question 2: Explain the lack of results.
Double click on the instrument and fix its position and its orientation. Run the simulation
again. You can lock your design if you want to avoid moving accidentally your objects.
Question 3: Note the size and orientation of the error ellipses by double clicking on the
points and looking in the “ellipse” tab (you may want to use the slider on the left to have
a nicer drawing).
Move around one point to look at the changes of the error ellipse.
Question 4: If you had used a total station instead of the tracker, what should you change
and what should you expect?
Now, unfix the tracker position, and fix the positions of all the points. Run the
simulation.
Question 5: Record the results.
Question 6 (for surveyors only): What is the name of the set-up you just simulated?
Now add another point and a tracker observation to this point and run the simulation
again.
Question 7: Record the results.
Question 8 (for surveyors only): What is the meaning of this operation?
Now unfix the first 3 points positions. Add 2 more points and a second tracker on the
right side of Point1. From the first tracker and the second tracker draw triplet
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observations to the new points. Draw also triplet observations from the new tracker to
Point2, Point3 and Point4. Run the simulation again.
Question 9: Record the results.
Question 10: Why does it work this time (and not during question 2)?
2. LCLS Injector Case
The previous example must have convinced you that entering manually a full network
may be a little tedious! This test case will demonstrate how to import information directly
into SIMS. There are 2 very different imports:
- the import of a CAD drawing (dxf format) to help visualize.
- the import of points only or of total existing network.
Start a new SIMS, go to the file menu and under import, choose the dxf file first (you
may have to re-center the drawing), then choose the text file. You are now ready to
design your own survey of the LCLS injector area.
To conclude, open the SIMS document called “Sector20 Actual Network” and zoom at
different locations to check on the different set-ups. Look at the choices of standard
deviations in the top split window. Would you have come to similar choices and designs?
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