LESSON 2
MAP READING
GRID REFERENCES
Reference:
Aids:
Manual of Map Reading and Land Navigation
1.
Slide 2/1 to 2/12.
Place of Work:
2.
1:50,000 map sheet per student.
Classroom
3.
Pencil and paper per student.
Student Dress:
4.
A pointer.
Working Dress
Administration:
Equipment:
1. Read the Instructors Notes before the
lesson.
Projector and Screen
2.
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3.
...........................................................
4.
...........................................................
5.
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Time Allowed:
40 Minutes
2-1
BEGINNING OF LESSON
STAGE
Revision
CONTENT
How are map scales shown on M726 maps?
ANSWER:
SLIDE 2/1
SLIDE 2/2
If we measure a distance on a 1:50,000 map of 4cm what will be the
equivalent distance on the ground?
ANSWER: 2km
What are the three items that identify a military map?
ANSWER:
SLIDE 2/3
Aim
The aim of this lesson is to teach you how to give a grid reference.
Objectives
By the end of this lesson students will be able to correctly identify map
detail by:
1.
Four-figure grid reference.
2.
Six-figure grid reference.
3.
Use of grid letters with grid references.
Reasons Why
So that you will be able to refer to positions on the map quickly and
correctly to the nearest 100 metres.
Incentive
During operations it is essential to be able to refer to targets and
features to within 100 metres on the ground. Use of the map grid and
grid references enables this to be done simply and quickly.
2-2
MIDDLE OF LESSON
MAP GRID
The grid is the name given to the two sets of parallel lines, one set
running south to north, the other set at right angles running west to east,
which intersect and form squares on the map.
Instructor to indicate on the map
MAP SQUARES
The intersecting blue lines or 2cm x 2cm squares on the map equal 1km
x 1km squares on the ground.
Every tenth kilometre line is thicker, and forms a 10 kilometre square.
The grid lines on your map are blue but the grid lines may be a different
colour on other map series.
Instructor to indicate on the map
EASTINGS AND
NORTHINGS
The vertical numbered grid lines start at the origin which is South West
of Cornwall, and increase successively going eastward - these are
called:
EASTINGS
The horizontal numbered grid lines also start at the same origin, but
increase successively going northwards - these are called:
NORTHINGS
SLIDE 2/4
GRID
REFERENCES
The numbered lines can be used to refer to a point of detail on the map.
The EASTINGS number is always followed by the NORTHINGS
number to form what is called a:
GRID REFERENCE (GR)
Instructor to emphasise:
EASTINGS followed by NORTHINGS
Any Questions
Questions from the class.
Confirmation
Questions to the class on grids.
What do you call the vertical grid lines that are numbered from left to
right across the map?
ANSWER:
Eastings.
FOUR-FIGURE
GRID
REFERENCES
A four-figure grid reference is made up from the two figure EASTING
followed by the two figure NORTHING, and is the point where the
lines cross.
SLIDE 2/5
A four-figure grid reference identifies the south-west corner of the onekilometre square east and north of where the lines cross.
DEMONSTRATE four-figure grid references using slide 2/6 and a
pointer.
SLIDE 2/6
2-3
REMEMBER:
“EASTINGS then NORTHINGS”
OR
“In the door then up the stairs”
SLIDE 2/7
Note that any zeros in either EASTINGS or NORTHINGS must
always be used, therefore:
03 not just 3
Any Questions
Questions from the class.
Confirmation
Questions to the class on four-figure grid references.
What is the name of the village in grid square
GR...............................................?
ANSWER: ..............................................................
What is the grid square containing ........................................
(Village name)?
ANSWER: GR ........................................................
Questions must relate to the map in front of the students.
SIX-FIGURE
GRID
REFERENCES
A four-figure grid reference is sufficient if you want to identify a large
object like a village or a unique object, for example the only bridge in
grid square 1234, or the only Place of Worship in grid square 1234.
However, you often want to identify positions more accurately than a
one-kilometre square.
A six-figure grid reference will identify a location to an accuracy of 100
metres.
SLIDE 2/8
This will identify the correct Place of Worship if there are two, or the
correct road junction.
Instructor to indicate the Place of Worship with a tower.
To give the EASTINGS OF A SIX-FIGURE GRID REFERENCE
you identify the grid line to the LEFT of the object, just as you did in
four-figure grid references. Then mentally divide the space between the
grid lines into tenths. You obtain the last figure by counting from the
left in tenths.
To give the NORTHINGS OF A SIX-FIGURE GRID
REFERENCE you identify the grid line BELOW the object, again
divide the square into tenths and count the tenths up from the bottom.
DEMONSTRATE using a different feature.
SLIDE 2/9
DEMONSTRATE using the M726 map on the slide.
2-4
Any Questions
Questions from the class.
Confirmation
Questions to the class on six-figure grid references.
Use slide 2/9 or the map in front of the students to practise six-figure
grid references.
SLIDE 2/9
LADDER GRIDS
It has already been said that each 10 kilometres blue line is thicker than
the other grid lines. If you look at your map you will see that the thick
lines also have the grid numbers printed against them, forming what is
called a “ladder grid”.
Instructor to show a highlighted ladder grid
GRID LETTERS
(FULL GRID
REFERENCE)
If you look at your map you will find BLUE LETTERS in each corner.
A grid reference is repeated after one hundred kilometres in any
direction and so Grid Letters are put on maps to make a Grid Reference
unique. On M726 maps the BLUE GRID LETTERS refer to the 100
kilometre square that the map lies within. Each 100 kilometre square
has unambiguous Grid Letters.
SLIDE 2/10
If you are working over a large area you MUST included the Grid
Letters making what is called a FULL GRID REFERENCE.
SLIDE 2/11
Every military map explains how to give FULL GRID REFERENCE
correctly.
SLIDE 2/12
Any Questions
Questions from the class.
Confirmation
Questions to the class on grid references and full grid references.
When is it essential to include the grid letters with a grid reference?
ANSWER: When working over a large area or when you need to be
unambiguous.
What is the abbreviation written at GR..............................?
ANSWER: ........................................................
END OF LESSON
Questions from the
Class
Questions on the whole lesson.
Test on the Whole
Lesson
Write down or give verbally four and six-figure grid references
including full grid references, using Slide 2/9 or their maps.
See Instructors Notes
Pack Equipment
Pass answer papers to the front.
Hand in stores.
Summary
A map grid is used to indicate positions on a map.
2-5
EASTINGS always come before NORTHINGS.
A four-figure grid reference defines a whole kilometre square east and
north of the intersection of the two grid lines, and is used for large or
unique objects.
A six-figure grid reference defines an AREA of 100 metres square, and
is used to define small objects.
Ladder Grids save the map being unfolded.
Grid Letters MUST be used with a grid reference to make sure there is
NO DOUBT in the position, if operating over a large area.
Look Forward
Being able to use grid references correctly to refer to places the map is
an important map reading skill. In the next lesson you will start
learning about the symbols on your map, the conventional signs.
INSTRUCTORS NOTES
1. At this stage conventional signs have not been taught and questions to the class should be
based on arbitrary positions. The problem can be overcome by the use of slides on which
letters or numbers are marked, by using a pointer and a slide, or by using test sheets showing
a grid and marked with letters or numbers. In Army Training Regiments with a high
training load, map extracts can be mounted on boards and locations marked with numbers
using washable felt tipped pens. Map Series GSGS 5676 Sheets 1 to 5 are designed to help
and may be obtained from the nearest Map Depot.
2. Teaching Grid Referencing before Conventional Signs will make it easier to present later
lessons.
3. The instructor should prepare sufficient examples and test questions before giving the
lesson.
4. Tests should include both the student identifying feature on the map, having been given a
grid reference, and the student having to five a grid reference for a particular feature.
5. The amount of confirmation or testing will depend on the aptitude of the class. Students
MUST become proficient at grid referencing before the next lesson because they are used
extensively in later lessons.
2-6