Grid references: pinpointing locations
FoundationGive locations with grid references: read eastings (vertical lines) first, then northings (horizontal lines). Four figures give a 1 km square; six figures are accurate to 100 m.
- Eastings = vertical lines; northings = horizontal lines
- Order: east first, then north
- 4 figures = 1 km square; 6 figures = 100 m precision
§Text Passage
1This lesson shows you how to report a location using grid references. The rule is 'eastings before northings': read the number on the easting line first, then the northing. A four-figure reference tells you which one-kilometre square you are in; a six-figure one is accurate to within 100 metres.
2Why split coordinates into eastings and northings? The blue grid lines give every point on the map a unique 'address', just like a house number. Dividing each square into tenths narrows a location down from 'which square' to 'which spot' — a system that rescue teams and planners rely on.
3All official Hong Kong maps use the unified Hong Kong 1980 Grid. Mountain-rescue reports to the police and trail markers from the Agriculture, Fisheries and Conservation Department all use six-figure grid references to pin down positions. Master this and every outdoor trip gets a little safer.
1Summary 重點摘要
Give locations with grid references: read eastings (vertical lines) first, then northings (horizontal lines). Four figures give a 1 km square; six figures are accurate to 100 m.
2Vocabulary cards Vocabulary
Numbers that state the position of a point or square on the map.
The vertical grid lines; values increase from west to east.
The horizontal grid lines; values increase from south to north.
Identifies a whole 1 km × 1 km grid square.
Two extra digits locate a spot inside the square, accurate to 100 m.
The square enclosed by two eastings and two northings.
The unified grid system used on all official Hong Kong maps.
Digits 5 and 6 of a 6-figure reference, dividing the square into tenths.
3Step by step Steps
- Know your linesThe vertical grid lines are eastings, their values increasing from west to east; the horizontal lines are northings, increasing from south to north. Woven together these lines form the blue grid that gives every point on the map a unique 'address'. Recognising the direction and numbering rules of the two sets of lines is the first step in reading grid references without error.
- East first, then northRead the references in the order 'eastings first, then northings', just as you walk along the corridor before climbing the stairs. For example, 3522 means the square enclosed by easting 35 and northing 22. A four-figure reference pins down a square roughly one kilometre wide; reverse the order and the location is completely wrong, so memorise 'east before north' and always write the figures in that order.
- Six figures = more preciseTo fix a position to within about 100 m, divide each square mentally into tenths: the fifth and sixth digits of the reference are these tenths, counted from the west and south edges of the square. Thus 286453 means easting 28.6 and northing 45.3 — a point six tenths across and three tenths up inside square 2845. Six-figure references pinpoint a spot inside the square and are the most commonly quoted form.
- Real-world useAll official Hong Kong maps use the Hong Kong 1980 Grid. When hikers get into trouble and call the police, rescuers rely on six-figure grid references to pin down the position, and the Agriculture, Fisheries and Conservation Department prints references on country-park trails for users. Note down your destination's reference before setting out, so that in an emergency you can state your position quickly and accurately and save precious rescue time.
- Use a ruler to judge tenthsJudging tenths by eye alone invites error: imagine each edge of the square divided into ten parts, first estimating how many tenths the target lies from the west edge, then from the south edge; measuring the edge with a ruler and dividing it into segments is still more reliable. A pavilion sitting exactly midway along the square in the east–west direction, for instance, has an easting tenth of 5. With practice this estimation becomes both fast and accurate in exams.
- Check before you reportAfter writing a reference, check three things: the first three digits are the easting and the last three the northing; the order has not been reversed; and the map confirms that the target really lies inside that square. When reporting to rescuers, add a nearby landmark such as 'by the pavilion in Lion Rock Country Park' so they can verify the position twice over. This habit of checking prevents a moment's carelessness from sending help the wrong way.
4Diagrams Diagrams
5Worked example Example
Example: a school sits inside square 2845, 6 tenths from the west edge and 3 tenths from the south edge. Write the 6-figure grid reference.
- Easting: 28 + 6 tenths → 286
- Northing: 45 + 3 tenths → 453
- East first, then north: 286453
- Check the order: easting first, northing second, three digits each
- Answer: The 6-figure reference is 286453. Eastings first: square 28 plus 6 tenths measured from the west edge gives 286; then northings: square 45 plus 3 tenths from the south edge gives 453; joined in 'east then north' order it reads 286453, accurate to about 100 m.
6Common mistakes Mistakes
7Quick check Quick check
Q1In what order do you read a grid reference?
Q2What does the 4-figure reference 3522 mean?
Q3How accurate is a 6-figure grid reference?
Q4Which of eastings and northings are vertical lines and which horizontal, and in which directions do the values increase?
Q5What do the 6 and 3 mean in the six-figure reference 286453?
8Recap Recap
- Eastings = vertical lines; northings = horizontal lines
- Order: east first, then north
- 4 figures = 1 km square; 6 figures = 100 m precision
- Official Hong Kong maps all use the Hong Kong 1980 Grid
- A grid reference is each point's unique address, vital for rescue and planning