# Triangulation

We can measure the distance to something far away by triangulating. In our lecture demonstration the triangulation board helps us make the necessary measurements.
 The triangulation board has a tiltable arm with a laser pointer on it. We use the following procedure to measure the distance across the lecture hall. A distant point on the wall is sighted by aiming the laser pointer horizontally along the top horizontal black line on the board. The arm is then moved to the bottom horizontal black line and tilted upward until the laser pointer aims at the same point as in step 1. The deviation of the tip of the arm above the lower horizontal line can be measured on the scale. In this case the value is 4.5 cm or 0.045 m. Other data needed to determine the distance are the distance between horizontal black lines, 0.7 m and the distance from the arm's pivot point to the scale at its tip, 0.8 m.
Below is the worksheet that accompanies the demonstration.
If you follow the instructions on the worksheet with the data given here, you should get a distance of 12.44 m. The actual distance is 12 m.

An error of a little more than 1 mm in measuring the pointer position could account for the error in our distance measurement.

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