Direction and Bearings
The main directions in a compass are north, south, east and west. This are shown in a purple
and white colour in the diagram. There are also North East, South East, South West and
North West this ones are the arrows in blue on the compass.
Bearings is the measurement of an angle between one point to another. They are measured
clockwise so for example the bearing from A to B is 25 and from B to A is 205. To measure a
bearing first you have to do a north line like shown in the diagram above and from there you
measure the angle of the curve until it touches the line connecting the two points.
Coordinates and Their Functions
We have already noted that a map is a working model of the earth or its parts. To know
whether this model represents the earth truly or not, we need a frame of reference to compare
the details of the real earth with that of its model. Geographic coordinates are the most
commonly used frame of reference. Another frame of reference is known as ‘grid system’.
The latest method of locating one’s position while moving of the land or navigating in the
ocean or air is the GPS.
Direction on Maps
Like distance, direction is difficult to measure on maps because of the distortion produced by
projection systems. However, this distortion is quite small on maps with scales larger than
1:125,000. Direction is usually measured relative to the location of North orSouth Pole.
Directions determined from these locations are said to be relative to True North or True
South. The magnetic poles can also be used to measure direction. However, these points on
the Earth are located in spatially different spots from the geographic North and South Pole.
The North Magnetic Pole is located at 78.3° North, 104.0° West near Ellef Ringnes Island,
Canada. In the Southern Hemisphere, the South Magnetic Pole is located in Commonwealth
Day, Antarctica and has a geographical location of 65° South, 139° East. The magnetic poles
are also not fixed overtime and shift their spatial position overtime.
Topographic maps normally have a declination diagram drawn on them. On Northern
Hemisphere maps, declination diagrams describe the angular difference between Magnetic
North and True North. On the map, the angle of True North is parallel to the depicted lines of
longitude. Declination diagrams also show the direction of Grid North. Grid North is an
angle that is parallel to theeasting lines found on the Universal Transverse
Mercator (UTM) grid system.
This declination diagram describes the angular difference between
Grid, True, and Magnetic North. This illustration also shows how
angles are measured relative grid, true, and magnetic azimuth.
In the field, the direction of features is often determined by a magnetic compass which
measures angles relative to Magnetic North. Using the declination diagram found on a map,
individuals can convert their field measures of magnetic direction into directions that are
relative to either Grid or True North. Compass directions can be described by using either
the azimuth system or the bearing system. The azimuth system calculates direction in
degrees of a full circle. A full circle has 360 degrees. In the azimuth system, north has a
direction of either the 0 or 360°. East and west have an azimuth of 90° and 270°, respectively.
Due south has an azimuth of 180°.
Azimuth system for measuring direction is based on the 360 degrees
found in a full circle. The illustration shows the angles associated
with the major cardinal points of the compass. Note that angles are
determined clockwise from north.
