Orientation in field conditions an important component of many professions. For this purpose use cards and compasses. For definition of the direction according to the card on a concrete object use a directional corner and magnetic azimuths.
It is required to you
- Compass or surveying compass, sharply ground pencil, ruler, protractor.
Instruction
1. A directional corner in geodesy call a corner between the line passing through this point the direction on a reference point and the line of the parallel abscissa axis lectured from the northern direction of abscissa axis. It is counted at the left on the rights (on the arrow course) from 0o to 360 °.
2. It is the most convenient to determine a directional corner by the card. A pencil, on a ruler, draw the line through the centers of conventional signs of a starting point and reference point. Length of the drawn line, for convenience of measurement, has to exceed protractor radius. After that, combine the center of a protractor with a point of intersection of lines and turn it so that zero on a protractor coincided with the vertical line of a grid on the card (or the line to it parallel). Count values of a corner in the direction of the course of an hour hand. The average error of measurement of a directional corner a protractor makes from 15/to 1 lakes.
3. Sometimes, for calculation of directional corners use magnetic azimuths. The magnetic azimuth is a flat horizontal corner the formed line directed to a reference point and the northern direction of a magnetic meridian. It counts also from 0o to 360o clockwise. Magnetic azimuths measure on the area by means of a compass or a surveying compass. The arrow of a compass, more precisely its magnetic field, interacts with magnetic field of the area and shows the direction of a magnetic meridian.
4. Further it is necessary to define the amendment of the direction (sum of rapprochement of meridians and magnetic inducement). Magnetic inducement call a corner between magnetic and geographical meridians in the set point. Rapprochement of meridians is a corner between the tangent which is carried out to a meridian of this point and a tangent to the surface of an ellipsoid of rotation which is carried out in the same point parallel to an initial meridian. The amendment of the direction is also counted also from the northern direction of a coordinate grid in the direction of the course of an hour hand. The amendment of the direction is considered to be positive if the arrow deviates to the right (on the East) and negative if deviates to the left (on the West). The magnetic azimuth measured by means of a surveying compass on the area can be transferred to a directional corner having added to it the amendment of the direction, attentively considering the sign of the amendment.