Calculation of a bias can be necessary during the geodetic works, when calculating a slope of a roof, or for other purposes. Perfectly, if you have a special device for these measurements, but if it is absent – be not upset, will be a roulette and make-shifts enough.

## It is required to you

- - inclination compass;
- - level gage;
- - level;
- - roulette;
- - lath;
- - calculator;
- - level.

## Instruction

1. It is the simplest to consider a bias by means of the inclination compass if you do not have it, try to make this simple device independently. Take a lath and attach to it a frame, in a corner of a lath arrange an axis with the pendulum. Make the pendulum of two rings, plates, a small weight and the index. At measurement the small weight will move between guides with cuts. Inside arrange a scale with divisions, having made it by means of a protractor.

2. For measurement of a bias of a roof apply a lath at right angle to the fad and look on what division of a scale the index stopped. You receive value of a bias in degrees.

3. To measure a bias by means of make-shifts without creation of the special device, mentally construct a rectangular triangle which inclined party will coincide with the inclined surface, one leg will be parallel to the earth, and the second – is perpendicular. Now your task is to find at least two parties of this triangle.

4. On the site of the earth or the road it is possible to use a level. Determine with its help point height above sea level and find a difference, and measure distance between points a roulette. If there is no level, just take a long board and arrange it strictly horizontally (level the level gage or in a national way). In the lower part for this purpose enclose bricks or other make-shifts under a board. Measure length of a board and height of bricks.

5. If an object is far, photograph it and measure length of the parties of a triangle in the photo. Find length of two legs – horizontal and vertical.

6. Now divide length of an opposite (vertical) leg into length of adjacent (horizontal). To receive a bias as a percentage, increase by 100% and if you increase result of division into 1000 ‰, then you learn a bias in per mille.

7. To find value of a bias in degrees, find the engineering calculator. It can be the ordinary electronic device with expanded functions or the Calculator program on the computer (it is possible to find also in the Internet online). Enter the number received as a result of division of legs and press the button an arctangent (atan or atg). You receive a surface bias in degrees.