12. Map Reading And Navigation

Question 1

Nav 1. Scale

A. What is a map
B. Limitations of features on a map
C. What does a legend show
D. What is scale and what scales are used

Answer 1

A. Birdseye view of the ground showing physical features, man made features and information relief (topographical map)

B. Features can change over time

C. Gives information to help interpret the map inc GMA and scale bar

D. Shows ratio between distance in the real world and the map (number of times map is smaller than the real world). Ratio can be in words fraction of scale. Will mostly use 1:50,000 (1km is 2cm on map) but sometimes 1:25,000

Question 2

Nav 2. Grid Reference System

A. What is GRS
B. How is GB divided on a map
C. What are the grid lines called?
D. What is a two figure grid reference?
E. What is a four figure grid reference?
F. What is a six figure grid reference?

Answer 2

A. Pinpoints a location on a map

B. Into 52 squares (100km2). Each square identified by a two letter reference

C. Vertical lines - eastings. Horizontal lines - northings. Both numbered 0-9.

D. Each square is 10km x 10km (I.e SY 19)

E. Each square is 1km x 1km (I.e SY 16 96)

F. Uses 1km x 1km square. identifies a feature. Use a romer (ruler on compass - to correct scale only) to identify the last figures. Line up the romer so the feature is in the corner of the romer. Identify easting reference then northing. (I.e SY 161 964)

Question 3

Nav 3. Tools

A. Name the features of the overall “Standard RM Issued Lightweight Compass”

B. Name the features of the compass element only

C. Name the features of the “Standard RM Issued RA Protractor”

Answer 3

A. 1. Compass mounted on rectangular clear plastic plate
2. Direction of travel arrow
3. Magnifying glass
4. Map measuring scales
5. Selection of romers

B. 1. cylindrical, filled with liquid and supports the needle on a central pivot.
2. Red needle always points north.
3. Outer circle/ bezel has graduated scale at 50mil intervals with index line to identify bearings
4. Inside circle has 4 orientating lines, a declination arrow and scale marked in degrees
5. Night features - needle pointing north, bezel highlighting the bearing, declination arrow, direction of travel

C. 1. Outer edge has two sets of graduated figures . Outer set 1 -3200 mils, inner at 3,200-6,400 mils at 10mils intervals
2. 1:50,000 scale on base. Parallel is a zero line with a different scale. In the centre of zero line is a hole where string is threaded through
3. Also has a number of different romers

Question 4

Nav 4. Methods of Measuring Distances

Answer 4

A. Use grid lines - least accurate but quickest (1km apart and 1.5 corner to corner in maps)

B. Use a ruler and measure distance between two points for start and finish and relate to scale bar - more accurate

C. Use paper and map each point on a route and then measure the first point against the last point and measure against the scale bar - most accurate

Limitation to all measure is they are as the crow flies (don’t account for contours). All methods should ideally account for this.

Question 5

Nav 5. Orientate Map

How do you orientate a map with:

A. A compass

B. Ground features

Answer 5

A.
1. Place compass on the map

        2. Ignore needle and turn bezel until declination arrows point north on map (grid north)/ orientating lines align with eastings 

        3. Rotate until compass red needle points in same direction as eastings
        4. Map is now orientated. Check land features.

B.
1. Find prominent features you can also see on the map (I.e church or tower)

        2. Turn the map until features are in line with feature on the ground

        3. Map should now be oriented

Question 6

Nav 6. Grid Magnetic Angle (GMA)

A. What is GMA

B. Where is the GMA information located

C. What SI unit of measurement is used for GMA?

D. How often does GMA change

Answer 6

A. difference between north on compass and north on a map. Use to change between magnetic bearings on your compass and grid bearings on your map.

B. Found at top of topographical map or in the legend

C. degrees or mils. For land the military uses mils.

D. Have to adjust the amount annually. Formula is Current year - year of map x annual change. Subtract this from the maps GMA equals the revised GMA (2011-2007=4. Then x 2.5mils = 10. Then subtract from the maps current GMA say 39mils =29 mils). Subtracting the GMA from a magnetic bearing gives a grid bearing. Or adding the GMA to a grid bearing gives a magnetic bearing (Mag to grid get rid. Grid to mag add)

Question 7

Nav 7. Take a Magnetic Bearing

A. From a map

B. From the ground

Answer 7

A.
1. Place compass on the map with long edge along line of travel (arrow points in direction of travel)
2. Turn bezel (ignore needle) so arrows point grid north and orientation lines in line with eastings
3. Read the bearing at the index line (in line with magnifying glass)
4. Change grid bearing to magnetic bearing by applying GMA
5. Compass now set for a magnetic bearing on the ground

B.
1. Keep compass away from metal objects (weapon)
2. Hold compass flat in hand
3. Point direction of travel line with feature you are travelling to
4. Turn bezel so declination arrow is in line with needle
5. Figure on index line is magnetic bearing

Question 8

Nav 8. Converting to a Back Bearing

Answer 8

1. May need to convert bearing back to your unknown position
   2. If bearing is less than 3,200 then Add 3,200 to get your back bearing
   3. If bearing is more than 3,200 then subtract 3,200 to get back bearing
   4. Example - if bearing is 4,900 mils (49 on bezel) then subtract 3,200 for a back bearing of 1,700 mils.

Question 9

Nav 9. Plotting on a Map

A. When you need to plot a bearing

B. How do you plot a bearing using a protractor

C. How do you plot a bearing using a compass

Answer 9

A.
1. During resection
2. Confirm route of march
3. Locate enemy position

B.
1. Place centre point over position you are taking the bearing from
2. Ensure baseline of protractor is parallel with eastings
3. Curve of protractor will face right if bearing is less than 3,200 or left if greater than 3,200 mils
4. With protractor in correct position. Then mark on the map
5. Remove protractor and draw line from start point to marked point and beyond ( example is enemy is 8.5km away on a bearing of 1,300mils, mark point on map for bearing and then measure 8.5km using correct scale)

C.
1. Set the grid bearing you’ve been given on you compass
2. Now place one of the long edges of the compass on the map and rotate until the declination lines point grid north
3. Draw line from start point along the edge of the compass and extend as required
4. Now plotted a grid bearing using a lightweight compass

Question 10

Nav 10. Resection - Locates the general area you are in

Answer 10

2. Orientate map and find 3 features on the ground you can see on the map
   3. Get out compass and line it with feature to get magnetic bearing. Convert it to a back bearing and apply GMA.(say 4,900 to church ddt 3,200 equals 1,700 mils ddt GMA)
   4. Go to map and find feature and plot grid reference from point
   5. Repeat for next two features
   6. Once three lines are plotted then it will give a triangle. Confirm this back looking at extract position on the ground. You can then work back a 6 figure grid reference

Question 11

Nav 11. Marching on a Compass Bearing

Answer 11

1. Ensure you’re marching on a magnetic bearing. May have to adjust grid bearing to magnetic bearing
   2. Once you have magnetic bearing then rotate bezel until the magnetic bearing figure is on the index line
   3. Hold compass in front of you until needle falls in line with declination arrows
   4. Find a feature on line of travel that can travel to without referring to compass. Undertake this until reach destination

Question 12

Nav 12. Producing Route Card

Answer 12

2. Divide route into legs and record each checkpoints grid reference
   3. Measure length of each leg
   4. Calculate grid bearing of each leg and magnetic bearing. Record both on card
   5. Record number of paces on route card
   6. Add a description for each leg with as many details as possible

Question 13

Nav 13. Folding a Map

Answer 13

1. Lay map flat on table with legend on RHS
   2. Fold map in half horizontally so bottom half goes below the top half
   3. Fold in half again and then back out to create a crease
   4. Fold one end into the middle crease and repeat on other side
   5. Fold one end back out to edge of map and on the other side
   6. Turn the map over
   7. Fold edge of the map into the centre crease and repeat on the other side
   8. Fold in half at centre crease to form a fan
   9. Run against a table to tighten creases
   10. Fold the map in half so the legend is still visible