Determination of longitude and latitude and grid reference for various locations on the topographic maps.
Topographic maps of Jamaica
Survey Department, Kingston is the government agency responsible for publishing topographic maps of Jamaica. The most commonly used topographic maps are t
he scales of 1:50,000 (covers an area of about 800km2) and 1:12,500 (area about 200km2). These maps cover quadrangles of the sizes of about 20 1/2 and 5 1/4 respectively.
Detailed large scale maps 1:5,000 and 1:2,500 are available for some parts of the island. However, these maps are generally planimetric and do not show relief.
Geographic north and magnetic north
The direction of true geographic north is toward the top of the map. This direction is always parallel to the lines of longitude unless otherwise indicated.
The directions of magnetic north pole and true geographic north do not coincide. The angle between these two directions is known as the magnetic declination. This angle is always indicated in diagrammatic form in the bottom right hand corner of the topographic map for a specific year.
See - 1:50,000 and 1:12,500 topographic sheets.
It is obligatory to calculate correct declination for every map and year.
The procedure to correct declination will be explained.
A bearing is the compass direction from one point to another. It is expressed in degrees west or east of true north (quadrant bearing), or in degree from 0 to 360 (azimuth bearing). This concept will be explained both in Lab. and field sessions.