Today I'm going to show you how to read a 6-figure good reference from a
topographic map. This is a topographic map of the Waimakariri River which is in
the Canterbury region of New Zealand. Topographic maps have a grid of lines
drawn on them. You can see the lines, some horizontal some vertical and each line
has a number corresponding to it. Grid references are very useful for finding a
location on a local scale. For example we might want to find the coordinates of
this building here just south of the river mouth. Now coming to a more simple
map you can see that the vertical lines are called eastings and that is because
they travel from west to east. The horizontal lines on the other hand are
called Northings and we call them northings because they travel from
south to north. The numbers go 25 26 27 and so on. The next important thing to
know is that every square gets divided into ten. When reading a grid reference
you always read the easting first and the northing second. This is the opposite to
the way you would read latitude and longitude where latitude is read first
and longitude is read second. Now I've got three examples but I'm going to do
on this simple map. I've put in small red points for A, B and C. First let's do a
reading for A. The easting would be 97 and because A is right on the line the
third number would be a zero. This is an easting of 970. If the red point
was halfway along the grid square over here, the easting would be 975.
One tenth along the grid square here would be 971. Two tenths
would be 972 and so on. Nine tenths along the good square would be
979. The northing for point A is 280. Therefore for full
six-figure grid reference for A would read as 970280.
Now for location B which is right here in the corner so I will read the easting
first. This is nine tenths along the grid square so I would say it is 989
easting. The northing is also nine tenths up the grid square so it reads is
319. The six-figure grid reference for B is therefore 989319.
And finally let's get the grid reference for location C.
This point is right in the middle of the grid square for both the easting and
northing. The easting will therefore be 005 and for the northings
that would be 255. The full six-figure grid reference is
005255. Now I've come back to the Waimakariri River topographic map
and I'm going to show you a worked example here. This building here is the
surf club and I'm going to find a reading for this so the easting would be
77. Now it is halfway across the grid square so the third number
would be five, so we would write 775 for the easting, Now if you
look over here at the northing you would follow these numbers at the side. The
first two numbers will be 96. The surf club is nine tenths up the grid squares so
I will write 969 northing. The full six-figure grid reference for the
surf club is 775969. And finally I'll do one more
example. I want the grid reference for this point
here where the Kaiapoi River is entering into the Waimakariri River. I will
highlight this point with my marker. Following the numbers along the bottom
the first two numbers for this grid square are 75. The river mouth is one
tenth along the grid square so the third number is
one, giving us an easting of 751. For the northing I'll follow the numbers on the
right-hand side of the screen. The first two numbers of the grid square are 95.
The river mouth is eight tenths the way up, therefore the northing is 958. The full
six-figure grid reference for the river mouth is 751958.
So I hope this helps you to be able to read a 6-figure good reference.