Map Reading and Interpretation
Senior 2 · Geography and Environment
Map Reading and Interpretation
Lesson 2 of 4
18 min
A topographic map of the Nyabarongo valley may show hundreds of houses, springs and footpaths. Saying "the spring near the bend in the river" is not precise; there are many bends. A grid reference is a short string of numbers that points to one exact spot on the map, so that anyone holding the same sheet finds the same place. It is a standard map-reading question in O-level examinations.
Survey maps are covered with a grid of numbered lines.
Eastings are always given first, then northings. A common way to remember: "along the corridor, then up the stairs".
A four-figure reference identifies a whole grid square. Use the easting on the left (west) side of the square, then the northing along the bottom (south) side.
| Easting 34 | Easting 35 | Easting 36 | |
|---|---|---|---|
| Northing 73 | |||
| Northing 72 | school ■ | ||
| Northing 71 |
In the sketch above, each label sits on the line at the left or bottom of its row or column. The school is in the square whose west edge is easting 34 and whose south edge is northing 72, so its four-figure reference is 3472.
A grid square on a 1:50,000 map covers 1 km by 1 km, which is still large. To find a single point, imagine each side of the square divided into ten equal parts (tenths).
The school stands 6 tenths of the way east from easting 34 and 3 tenths of the way north from northing 72.
Check your answer by reversing it: 346723 means "34 and six tenths across, 72 and three tenths up". If that lands on the school, the reference is right.
Some features are big, like a forest or a swamp. For those, use a four-figure reference, or give the six-figure reference of the feature's centre.
Tip
Memory hook. "Along the corridor, then up the stairs": eastings first, northings second. The most common mistake is reading the line on the right or top of the square. Always use the lines to the left and below.
Solution: west line 42, south line 17: 4217.
Solution: 42 + 6 tenths = 426; 17 + 3 tenths = 173. Answer: 426173.
Solution: on the line means 0 tenths: 580. Northing: 095. Answer: 580095.
Solution: the northing was written first. The correct order is easting then northing: 346723.
Summary
Sources and credits
The grid sketch, worked example and practice items are written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
