# Simple Theodolite

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## Introduction: 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.

## Step 1: Tools Required

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

## Step 2: Materials Required

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

## Step 3: Cutting the Cardboard

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.

## Step 4: Draw the Semicircle

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).

## Step 5: Making the Moveable View Finder

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.

## Step 6: Attaching 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.

## Step 7: Making the Plumb Line

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.

## Step 8: Using the 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.

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.

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