Unit 21: Finding the location and time of our destinations

(A) What are latitudes and longitudes ?

Latitudes and longitudes

Are north-south and east-west imaginary lines drawn on the earth’s surface

Are similar to grid lines

Are measured in degrees (1 degree = 60 minutes; 1 minute = 60 seconds)

Show the absolute location of a place on the earth

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Unit 21: Finding the location and time of our destinations

Latitudes

For examples:The latitude of Hong Kong is 22N and Sydney is 33S.

Are numbered in degrees from 0 to 90 The equator is latitude 0 - the longest latitude which

divides the earth into Northern Hemisphere and Southern Hemisphere.

A place north of the equator is marked a number of degree north; whereas a place south of the equator is marked a number of degree south.

The North Pole and South Pole are 90°N and 90°S.

Are imaginary lines running parallel from west to east around the earth

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Unit 21: Finding the location and time of our destinations

Longitudes Are imaginary lines running from north to south which

join the two poles Are also called meridians The meridian passing through Greenwich near London

is the Prime Meridian.

For examples:Hong Kong is 114E and New York is 76W.

All longitudes to the Greenwich meridian’s east are marked east; whereas those to the Greenwich meridian’s west are marked west

180E and 180W are in fact the same line, so it is just called 180.

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Unit 21: Finding the location and time of our destinations

(B) How do we find the latitude and longitude of a place from an atlas ?

Suppose we want to find the location of Guangzhou in an atlas: We should look for the place in the index We may have the following information:

Guangzhou 23 5N 113 10E 28

Latitude Longitude Page

The last number is the page on which you can find a map showing Guangzhou.

When you turn to page 28 in the atlas, you can find the location of Guangzhou. Next

Unit 21: Finding the location and time of our destinations

(C) How do we find the local time and standard time of our destinations ?

Using longitudes to work out the time of different parts of the world There are 360 of longitude The earth rotates on its axis from west to east . It takes

24 hours to complete one rotation. This means the earth takes 4 minutes to rotate by 1 of

longitude and one hour to rotate by 15. We can use longitudes to work out the time of different

places. Hong Kong is on 114E. If our time is 8 a.m., then the

place on 129E should be one hour ahead of us, i.e. 9a.m. whereas the place on 99E should be one hour behind us, i.e. 7 a.m. Next

Unit 21: Finding the location and time of our destinations

Local time

Is worked out based on the longitude of the place

For every 1 of longitude east of Hong Kong, the local time will be 4 minutes ahead of our local time

Likewise, for every 1 of longitude west of Hong Kong, the local time will be 4 minutes behind our local time

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Unit 21: Finding the location and time of our destinationsStandard time

If every place sticks to its local time, it will be very confusing.

In order to solve this problem, the earth is divided into 24 time zones.

Each time zone covers 15 degrees of longitudes.

There is a difference of one hour between one time zone and the next.

All the places within the same time zone have the same standard time.

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Big countries like China cannot give one single time because they extend a large number of longitudes.

Unit 21: Finding the location and time of our destinations

Examples:Hong Kong lies in the Standard Time Zone of 120°E; whereas London lies in that of 0°. Therefore, the Standard Time of Hong Kong is 8 hours ahead of London.

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Unit 21: Finding the location and time of our destinations

Terms to learn: Latitude - an imaginary line running across the world

from west to east

Longitude/meridian - an imaginary line running from north to south joining the two poles

The Prime meridian - the 0° longitude passing through Greenwich near London. It is also called the Greenwich meridian.

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Unit 21: Finding the location and time of our destinations

Latitudes

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Unit 21: Finding the location and time of our destinations

Longitudes

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Unit 21: Finding the location and time of our destinations

Standard time

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