What are cardinal points? A compass has four main (or cardinal) points: north, east, south and west. These four cardinal points are used to describe direction. For example, if you are facing north, south is behind you, east is to your right and west is to your left. To give more accurate directions, the four cardinal points are divided into intermediate points: north-east, south-east, south-west and north-west. For an even ýner deýnition, we can further divide the intermediate points (see FIGURE1 ). For example, between north and north-west, is north-north-west (NNW); between north-west and west is west-north-west (WNW) and so on. Cardinal and inter-cardinal points are used in wind roses.
FIGURE1 A compass
Compass direction (e.g. NNW)
N
0
Bearing (e.g. 270°)
Why are wind roses useful? Wind roses are useful because they allow us to quickly see patterns in relation to wind direction, speed and frequency. Interpreting a wind rose To interpret a wind rose, remember the following points: • Wind roses have the rays drawn towards the centre. In FIGURE2 the longest ray is from the south- west, which shows that most of the wind is south-westerly. It is most frequent . • The circles around the image represent the various percentages of occurrences of the winds. For example, if the ray to the south just reaches the 20 per cent ring, it means a frequency of 20 per cent blowing from that direction. • The rays use symbols and colour to show wind speed . The FIGURE2 wind rose shows data for eight points of the compass.
Jacaranda Humanities Alive 7 Victorian Curriculum Third Edition
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