Concepts tested on June 2007 paper

As I had promised in the previous lesson, I will begin to discuss the question paper for the last examination (June 2007). I have already identified the concepts which were tested in Question 1. These are:

• Six-figure grid reference
• Measuring distance
• Calculating gradient
• Giving direction in terms of compass bearings
• Describing vegetation
• Describing landform

The map extract given in the examination was a section of St. Kitts, one of the Leeward Islands. A portion of that extract is published with today's lesson. I will be making reference to it from time to time as I go through aspects of Question 1. Please keep it safe so that you can practise the different map reading skills as I discuss them. Let me begin with grid reference.

If you need to locate places, then grid references are given. To give the exact location of a point (namely, a spot height; a trigonometrical station; where two roads intersect or the confluence of a stream) or a place (namely, a church, a school) then a six-figure grid reference is given.

Vertical, horizontal lines

However, use a four-figure grid reference to identify an area (namely cultivated crops, natural vegetation).

Look at the section of the map published. Notice that there are vertical and horizontal lines on it. The vertical lines are called eastings. Observe the numbers on these lines moving from left to right, or, better yet, from west to east.

They have the numbers 19, 20, 21, etc; in short, they increase going eastwards. The horizontal lines are called northings. Again, in reference to the given map extract, you would observe that they increase moving from the bottom upwards, or, from south to north. They have the numbers 10, 11, 12, etc.

Now, when giving a grid reference, you must state the easting before the northing. You use the easting to the west (or left) of the grid where the place or point is located, and the northing to the south or bottom of the same grid.

For the six-figure grid reference, a third digit is added, both to the easting and the northing. To obtain the third digit, you need to divide the area between the two adjacent lines, that is, easting or northing, into 10 equal parts.

You may estimate it but to be more accurate, take a bit of paper, extend it between the two grid lines, mark the points of the two lines on the paper, then use a ruler to mark off accurate divisions between the points on the paper. Let me go through this by referring to the question given.

(a) What is the six-figure grid reference for the trigonometrical station K48 at the end of East Pier on the coast in Basseterre?

Refer to the map extract and locate the trigonometrical station. The easting to the west is numbered 23. Extend a bit of paper between easting 23 and 24.

Use your ruler to divide that space into 10 equal parts. For this extract, each division is four mm apart. Put back the marked paper on the extract at easting 23 and make sure it passes through the trig station.

Notice that the station falls between the first and second lines. Your third digit then could either be one or two. The easting then is either 231 or 232. Apply the same method to the northing starting from the one to the bottom of the grid, that is, 11.

Having put the ruled paper in place, you would notice that the seventh division is on the point. The northing then is 117. Your answer for the question is 231117 or 232117.

As further practice, state the grid reference for the following:

(i) The trig station K12
(ii) The trig station K9
(iii) The Factory Pier at Fort Smith
(iv) The reservoir at Buckleys Estate.

Marjorie Henry is a vice-principal at Glenmuir High School and is head of the Geography Department. She teaches the subject at the CSEC Level.