Basic calculations of distance and area on the maps
DISTANCE ON THE MAP
One may be asked to calculate or measure the distance of a river; road, railway, electric transmission line etc on the map. It should be noted that some of theses distances may be straight while others may bne winding.
Measurement of straight line distances on the map.
To measure a straight line on the map, a pair of dividers or a straight edge of paper are the best instruments to be used. To measure two points on the map on a straight line, the two points must be identified first, using grid reference values. Open or stretch out the arms of the pair of dividers to fall exactly on the two points along the straight line, or if it is the edge of paper, it should be placed along the straight line to cover the two points A - B and then marked out on the paper. After opening the pairs of dividers or making the two points on the edge of paper, these two are taken and placed along a graduated ruler to get the reading in centimeters. This reading in centimeters is not the ground didtance and so must be converted to actual ground distance which is always in kilometers.
Measurement of a winding distance or course
To measure a winding distance an a map, a string or thread and paper edge can be used.
- MEASURING WITH A PIECE OF PAPER