How to find a directional corner

How to find a directional corner

Orientation of the line according to the card consists in definition of its direction of rather geographical, axial or magnetic meridian taken for the initial direction. The initial and chosen direction form an orient corner by means of which there is an orientation of the direction of the line. The directional corner, a true (geographical) and magnetic azimuth or points can be an orient corner: geographical, magnetic and directional.

It is required to you

  • - topographic map,
  • - protractor,
  • - ruler,
  • - pencil,
  • - calculator,
  • - compass.


1. A directional corner is called the corner formed by the northern direction of an axial meridian (initial direction) and the line of the direction on a reference point. The directional corner clockwise is counted and measured in limits of 0-360 degrees.

2. There are several ways of finding of a directional corner: by means of a protractor, a magnetic azimuth (using a surveying compass or a compass), a geodetic way, gyroscopic, astronomical, by means of a hordouglomer and on planimetric to points maps or aerial photo shoots. Let's consider some of these ways.

3. With the help to a transportiraprovedita a straight line through a starting point and a reference point to the closest vertical line of a grid of coordinates on the card (abscissa axis). It is important that the distance from a starting point to a point of intersection of the drawn line with abscissa axis was not less than the radius of a protractor.

4. Combine a protractor with abscissa axis: the center of a protractor has to be in a point of intersection of a vertical coordinate axis and the line of the chosen direction, and zero line of a protractor - to look at the North.

5. Measure a corner between the vertical line of a grid of coordinates and the drawn line of the direction: counting from abscissa axis (northern direction) - clockwise.

6. By means of formulas it is possible to pass from one orient corner to another, say, from a magnetic or geographical azimuth to a directional corner.

7. Calculation of a directional corner by means of magnetic you azimutavychislit a geographical azimuth. It is equal to the sum of a magnetic azimuth and inducement of a magnetic needle (data are specified on the card — the scheme of interposition of meridians in the bottom of the card). This amendment can be with the sign ""+" or "" -"".

8. Subtract the size of Gaussian rapprochement of meridians from the received value of a geographical azimuth (the value is specified in the scheme of interposition of meridians). The received number is also a directional corner of the direction.

9. Calculate an azimuth of the chosen star (after long observations). Then calculate or define directly by a nozzle on a surveying compass an azimuth of the focused direction. Later calculate a directional corner on a formula. This way of determination of size of a directional corner is called astronomical. It is the most exact.

Author: «MirrorInfo» Dream Team