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MAP READING

 MAP READING

What is a map?

A map is representation of selected natural and manmade features of the whole or part of the earth's surface on a flat sheet of paper on a definite scale and in their correct relative geographic positions and elevations.

What is conventional sign?

Conventional signs are symbols used to represent certain artificial or natural features/ objects on the map. They are seldom drawn to scale.

What is scale?

By scale it means the proportion which the distance between two points on the map bears to the distance between the same two points on the ground.


Define important technical terms used in map reading? 

(a) Bearing - The angle formed by a line joining two points and the North and South line. Bearings are always measured clockwise. 
(b) Bench Mark - A permanent mark usually cut into a wall recording exact height for future reference, marked BM with the height on Ordnance Survey Maps. 
(c) Contours - A line drawn on the map joining up all points of equal height above sea level. 
(d) Gradient - The slope of a hill expressed as a fraction.
 (e) Grid Lines - Lines running parallel to and at right angles to a North and South line through approximately the centre of the area covered by the grid system. 
(f) Grid North - Except through the origin, grid lines do not lie true North and South or East and West, Grid North is the direction of the North South grid lines on a map. 
(g) Magnetic - The difference between true North & Magnetic Variation North.
 (h) Setting - Placing a map so that North on the map points toward the North so that the objects on the map are placed in relationship to the same objects on the ground. 
(j) Trig Point - A point fixed during the triangulation at the beginning of a survey, marked on Ordance Survey Maps by a small triangle with the height.
 (k) True North - The direction of the North Pole from the point.   

Define important Topographical terms used in map reading?

 (a) Basin - An area of fairly level ground surrounded by hills or the area drained by a river and its distributaries. 
(b) Col or Saddle - A narrow ridge of high land joining up to higer hills.
 (c) Crest - The highest part of a hill or mountain range. It is that line on a range of hills or mountains from which the ground slopes down in opposite directions. 2 
(d) Dead Ground - Ground which by reason of undulations or hills is not visible to the observer.
 (e) Defile - Any feature whether natural or artificial which could cause a body of troops to contract its front. An example of a natural defile is mountain pass while a bridge is an example of an artificial defile.
 (f) Escarpment - The steep hill side formed by a sudden drop in the general ground level usually from a plateau. 
(g) Knoll - A small isolated hill. 
(h) Plateau - A table land, an elevated region of considerable extent generally fairly level.
 (j) Ridge - The line along a hill or range of hills or mountains from which water flows in opposite directions, a divide, sometimes and the crest of a line of hills as it appears along the horizon.
 (k) Watershed - The line separating the water flowing into two different river systems, the edge of a river basin

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