Compass and Mapping 2
Be able to show your ability about the under mentioned
a) Conventional signs of a map b)Setting a map c) Make a rough map to scale using map making by triangulation (using a compass or otherwise)
A map is a picture of a given area of what the ground looks like from directly above. When undertaking a journey, we need to be able to find our way around competently, sometimes in unfamiliar territory. It is then that we need to be able to use and read maps. The type of map required will depend upon the journey or destination.
A simple sketch map is maybe all that is required to find a room or building, or it may be a road map which helps you plan long distance routes across a whole country. There are also town maps and Ordnance Survey maps. All maps are drawn to a scale which means that a defined length on the map equates to a real length on the ground, for example one cm = one km.
Parts of a map
Road Maps
When travelling by road it is important that maps show routes clearly. One purpose of these maps is to show easily the type of road that you are either on, or wish to be on. It may be a straight, wide road like a motorway which will allow many miles to be travelled at high speed or it could be a narrow, winding road that twists through villages and towns. All recognised routes in the United Kingdom have a number. For example, motorways are numbered M1 upwards. Other major roads carry the prefix letter A and then more minor roads are prefixed with the letter B and so on. On a road map, these different classes of road are differentiated by colour. At crossroads and major intersections, signposts state not only the place but the road numbers as well. A motorist reading from a road map can read the number easily and quickly on the signpost. A map will also show you whether the roads will take you through built up areas or whether there is another route, a by-pass or the possibility of enjoying a more scenic journey.
Town Maps
A town map concentrates on important buildings and other features in the town as well as the streets and roads. Due to the amount of detail, the features might be numbered, in which case you would refer to a key at the bottom or side of the map. Much more detail, including all the street names, might be placed in a separate key in alphabetical order and this might include a reference to enable you to locate a point of interest on the map. In this case, the map will be divided into squares (or grids) with letters along the bottom and numbers up the sides. In the example below, the Police Station on the map would have the reference A8 in the key.
Ordnance Survey (O.S.) Maps
Ordnance Survey produce very detailed maps which are the most commonly used for hiking and expedition type activities. They show all features including footpaths, hills, valleys, water courses, railway lines, built up areas and so on. Thin orange-brown lines called contour lines on these maps indicate the height of the land above sea page 2 of 6 level and their shape indicates the shape of the land itself. Lines drawn close together indicate that the land rises or falls (that is gains or loses height) rapidly, while contours spaced more widely apart show that the slope, either up or down, is more gentle. Each contour will have its height above sea level printed on it at intervals so it is easy to decide if the ground is rising or falling.
Symbols
Map symbols are the signs or diagrams shown on a map to indicate physical features. A list or 'key' of what these symbols mean is given at the same point on or in the map for identification. A number of the more common map symbols are shown below. These will be consistent on all modern O.S. maps but they might vary on other sorts of map, so it will be worth checking that on the map you are using that the symbol means what you think it does!
Participate in our mapping sessions for more information
Attached Survey Department Map manual is for your reference
How to make and scale a map with triangulation
Map Scale
This section is updated as of 24/4/2024, referenced from the Compass, Mapping & Hiking Guidebook by Colombo District Programme Team - Provided by Mr. Irshad Razak Zonal ADC
Map scale refers to the relationship or ratio between distance on a map and the corresponding distance on the ground.
Examples for different Scales
1:50,000
1:25,000
1:12,500
1:50,000
Convert both sides to cms and treat both sides as cms
1cm = 50,000cm
1cm in the Map is equals to 50,000cm on the ground.
1cm = 50,000cm
1cm = 50,000cm / 100 (To convert centimeters to meters)
1cm = 500m
1cm = 500m / 1000 (To convert meters to kilometers)
1cm = 0.5Km (1cm of the map indicates 1/2 kilometers)
To make it readable and understand easily, calculate what 1km represent in this scale
1cm x 2 = 0.5Km x 2
2cm = 1Km
The map indicates that 1 centimeter on the map represents half a kilometer on the ground, and 1 kilometer on the ground is depicted as 2 centimeters on the map.
1:25,000
Convert both sides to cms and treat both sides as cms
1cm = 25,000cm
1cm in the Map is equals to 25,000cm on the ground.
1cm = 25,000cm
1cm = 25,000cm / 100 (To convert centimeters to meters)
1cm = 250m
1cm = 250m / 1000 (To convert meters to kilometers)
1cm = 0.25Km (1cm of the map indicates 1/4 kilometers)
To make it readable and understand easily, calculate what 1km represent in this scale
1cm x 4 = 0.25Km x 4
4cm = 1Km
The map indicates that 1 centimeter on the map represents a quarter kilometer on the ground, and 1 kilometer on the ground is depicted as 4 centimeters on the map.
1:12,500
Convert both sides to cms and treat both sides as cms
1cm = 12,5000cm
1cm in the Map is equals to 12,500cm on the ground.
1cm = 12,500cm
1cm = 12,500cm / 100 (To convert centimeters to meters)
1cm = 125m
1cm = 125m / 1000 (To convert meters to kilometers)
1cm = 0.125Km (1cm of the map indicates 1/8 kilometers)
To make it readable and understand easily, calculate what 1km represent in this scale
1cm x 8 = 0.125Km x 8
8cm = 1Km
The map indicates that 1 centimeter on the map represents a 1/8 kilometer on the ground, and 1 kilometer on the ground is depicted as 8 centimeters on the map.
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