Conventional Signs

Map Scales and Measuring Distance

Lightweight Compass

Setting a Map by Landmarks

Releif and Vertical Interval

Back Bearings

Resection: Position Finding

Map and Compass: Powerpoint Files

It is important to note that you are not expected to learn these symbols parrot fashion but through experience on the ground.

Map Scales 

 The Scale of the Map must be known to enable you to Measure the Distance on a Map

 

•

•It would be impossible to make maps the size of the landscape it represents

••Maps scaled down proportionally to ensure they are easier read

 

•Method used to tell us about scale is Representative Fraction (RF)

•RF we usually use is 1:50,000

•Most British maps now metric

•The essential connection is the SAME unit of measure applies to both map and ground

 

•A Distance of 1cm on a 1;50000 map = 50,000 cms on the ground

•A distance of 1 metre on a 1:50000 map = 50,000 meters (50 Kilometres) on the ground

•2 centimetres to 1 kilometre  (One Grid Square)

 

1 Kilometre = 0.6214 miles – 1 Mile = 1.6093 kilometres

 

•All maps printed with graphic linear scales

•Found on the bottom centre margin of the map

•Contains Kilometre, Mile and Nautical Mile scales

 

•Shows up to 20km/12 miles/10 Nautical Miles distance

 

 

 

Map Scale - Sub-Divisions

  Introduction to The Lightweight Compass 

 The Silva Compass

Degrees are now used in all ACF map reading

Sign for degrees is e.g. 360°

 360° degrees in a circle

 60 minutes in a degree

 

Four Cardinal Points

North, South, East, and West    (N,S,E,W)

 

  

§Intermediate Points – NE,SE,SW,NW

•North = 360°

•East   = 90°

•South = 180°

•West  = 270°

 

The Mils System (Used by the Military)

Cadets now use the Degree System to keep in line with schools and the D of Ed Scheme

•Standard military system to divide the circle of a compass into 6400 mils

•0 or 6400mils is at the North Point

•There is 18 mils in a degree
May be used as an interest period at 4 star

North Points

•There are 3 North Points that we use:

•True North – the actual distance of the geographical North Pole

•Grid North – The direction of the Vertical Grid Lines on a map.
For all purposes True North and Grid North are the same

•Magnetic North – The direction towards which the compass needle is attracted  is the Magnetic North Pole

 

Top of Page

  Relief and Vertical Interval

•The Aim of this lesson is to teach you how to understand the shape of the ground in terms of hills and valleys.

•Contours on a map are known as “Relief”

 

§Lines on a map (usually red/orange) which join up points of equal height.

§Climb upwards in 10 meters on a 1:50,000 map

§Figures are written against the line to illustrate their height.

 

Contour Lines

  

nThe further apart the lines, the flatter the ground

The closer apart the lines, the steeper the ground

 

 

 

Top of Page

Back Bearings

The bearing you would use to retrace your steps.

Not necessary to move to the observation point as the back bearing can be calculated

Calculating a Back Bearing

• If your forward bearing is less than 180° you should add 180°

• e.g. Forward bearing of 95° you add 180° which leaves you with a back bearing of ?

+180

275°

• Once completed lay the new bearing onto your compass

Back Bearing

• Keep the compass on the Forward Bearing you have taken

• PRACTICE MAKES “PERFECT”

Top of Page

PDF Files

http://www.eglintonarmycadets.com/PDF/Conv Signs.pdf

Top of Page