Transcript Grid regerences made easy (PPS, 440kB)

GRID REFERENCES
MADE EASY
Produced by David Morris
A GRID REFERENCE is a number which
gives a location on a map
They are very useful in Scouts when we’re
out hiking
We can use them to find out where we’re
supposed to be…
...or if we get lost we can tell someone
where we are
The grid references we usually use are
SIX FIGURE references
They will look something like this:
216409
A bit like a phone number
These numbers refer to the GRID which
covers all maps
Here they’re marked in PINK so you can
see them, but they’re usually BLUE
42
The grid is labelled with GRID
NUMBERS at the bottom and left sides
of the map
41
40
20
21
22
23
The numbers at the bottom are called
EASTING because they show how far
East you are. They label these lines…
20
21
22
23
42
The numbers at the side are called
NORTHINGS because they show how far
North you are . They label these lines…
41
40
Each Easting refers to the column to the
right of it’s grid line
21
Each Northing refers to the row above
it’s grid line
40
Where are these EASTINGS and
NORTHINGS in the Grid Reference?
40
21
216409
EASTING
NORTHING
Both numbers combined give a square
on the map...
The grid
reference of this
square is 21 40
40
21
How do you remember WHICH COMES
FIRST though?
EASTINGS FIRST
One way of remembering is to read the
numbers ALONG the bottom
(EASTINGS) and then those UP the side
(NORTHINGS) because you go ALONG
the hallway in a house before going UP
the stairs
EXERCISE ONE
FIND THE SQUARE
You’ll have a map between two, and a list of 6 figure grid
references - just find the big square for each one
OK so we now know how to find the
square from these numbers:
6409
216409
21
But what about these ones?
What are they for?
Well the 40 and 21 only give you a big
square one kilometre wide!
1km
40
21
Not much use if
you need to
know where to
go exactly!
So we split each square into 100 smaller
squares...
Each square is labelled like the
grid before, but with just one
number from 0 to 9
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9
So, same as before, a square is identified by
an EASTING and a NORTHING
Remember, EASTING first
So what’s the
two numbers
which identify
this square?
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9
That’s right: 4 and then 7
4 first as it’s the EASTING
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9
Then 7 as it’s the NORTHING
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9
42
OK, let’s put it all together…
See the spot height marked 375 in the
square below?
41
40
20
21
22
23
42
Let’s find out it’s full 6 figure reference
______
41
40
20
First, what square is it in?
21
22
23
42
Yes, 21 - 40
But where does this fit into the 6 figure
reference?
41
40
20
21
22
23
42
21____
21 first
41
40
20
21
22
23
42
21_40_
Then 40
41
40
20
21
22
23
42
Both together...
21_40_
41
40
20
21
22
23
42
Now we need to look at the missing two
figures:
21_40_
41
40
20
21
22
23
42
21_40_
So we add the grid - usually you do this
in your mind
41
40
20
21
22
23
42
21_40_
The spot height is in this square
41
40
20
21
22
23
9 Zooming in...
8
7
2
212
_40_
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
8
9
42
So now we have the full grid reference:
212402
41
40
20
21
22
23
42
41
OK, what about the station in Llangollen?
______
40
20
21
22
23
42
41
Answer:
214422
40
20
21
22
23
OK, where’s this one...
204408
42
41
40
20
21
22
23
204408 Answer: Bank Fm
42
41
40
20
21
22
23
EXERCISE TWO
PRACTISE MAKES PERFECT
You’ll have a map between two, challenge each other to give
the grid ref for a place, and the places for given refs