Simple Theodolite

Theodolite is an instrument used for measuring angles. This instrument is very useful for calculating the heights and distances of objects .

Today we will learn how to make a simple theodolite.

1. Scissors
2. Glue
3. Protractor
4. Ruler
5. Marker pen
6. Compass (the one which is used to draw circles)

1. Cardboard
2. Thread
3. Paper Fastener
4. White paper
5. Small plastic sheet
6. Small object

Cut a piece of cardboard in which Length = 36 cm & Breadth = 21 cm.

You could also cut it smaller or larger but make sure that you could a semicircle using the maximum radius of the Compass.

Paste white paper on the cardboard.

Now, construct a semicircle :

1. Keep the tip of compass at the mid-point of the length.
2. Extend the compass to its maximum length and draw a semicircle.

Leave space of 4 cm (in width) and then draw a line that is equal to the length of cardboard.

Use the protractor to draw a perpendicular from the mid-point of the line. The point where the line meets the semicircle is the horizontal level of the eye, name it 0 degree.

Mark the angles 10, 20, 30,........,80,90, from the 0 degree angle on both sides (that is on the left and right sides).

Now, lets make the viewfinder.

Cut a piece of cardboard , make sure that it's length is greater than the radius of the semi-circle (we keep the length greater than radius so that we could display the angle measurements). Now, cut out a small piece on the top which would be used to display the measurement of the angle.

Take a piece of paper and make a hole (or a rectangular cut) in it. Paste a plastic sheet on the hole.

Now, paste the paper on the cardboard .You have made the viewfinder.

Use a fastener to attach the viewfinder at the mid-point of the line segment(or at the centre of semicircle) .

Make sure that it moves and displays all the angles.

Take a piece of thread that is longer than the length of cardboard, attach one end to the the top of cardboard and the other end to an small object.

Now you have made your own theodolite.

1. Keep the viewfinder at 0 degree .
2. Let the plumb line hang freely.
3. Keep the theodolite in vertical position.
4. Keep your eyes at the mid-point(or centre of semicircle) and see through the viewfinder.
5. Let us say that you want to see a top of the building, move the viewfinder until you see the top of the building.
6. Now, read the measurements.

Note : While performing this activity, make sure that the plumb line is parallel to the length of cardboard, this would help you to get more accurate measurements.