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Square kilometre

math Maturity 11-13 Next article →

A square kilometre is a way to measure area. Area is the size of a flat surface. We use this unit to talk about large spaces like cities or parks. One square kilometre is a very big amount of space. It is equal to one million square metres. It is also equal to 100 hectares.

Caldey Island map 1952
Caldey Island map 1952

You can also think of it in other ways. It is about 0.3861 square miles. It is also close to 247.1 acres. Scientists use the symbol km2 to write it down. This symbol means a square that is one kilometre on each side.

Map makers use these measurements to help us find our way. They often draw grid lines on topographical maps. On some maps, these lines are one kilometre apart. Each square made by the lines shows one square kilometre of land.

Caldey Island map 1952
Caldey Island map 1952

Different maps use different sizes for these squares. On a 1:100,000 map, each square is one square centimetre. On a 1:50,000 map, the grid lines are 2 cm apart. This makes each square 4 square centimetres in area. On a 1:25,000 map, the lines are 4 cm apart. Each square there is 16 square centimetres. All these squares still represent one square kilometre on the Earth.

Many old cities in Europe were built this size. Long ago, people built large walls to protect their homes. The space inside these walls was often about one square kilometre.

Dimensions of the old city of Delft
Dimensions of the old city of Delft

You can still see where these walls used to be. In Brussels, a ring road follows the old wall. In Frankfurt, the walls were replaced by gardens. Some cities were shaped like rectangles or ovals. The city of Delft in the Netherlands was roughly rectangular. Its area was about 0.9 square kilometres. The city of Lucca in Italy is also near this size. Its area is about 1.088 square kilometres.

Nature and sports also use these measurements. Many large parks are almost exactly one square kilometre. Examples include Riverside Country Park and Brierley Forest Park in the UK. There is also Jones County Central Park in Iowa.

Dimensions of the old city of Delft
Dimensions of the old city of Delft

Golf courses are often near this size too. A typical 18-hole course needs about 80 hectares. This is equal to 0.8 square kilometres. The Manchester Golf Club in the UK is one such example. Other courses include Northop Country Park in Wales. The Trophy Club is in Indiana, USA. Even the Old City of Jerusalem is nearly one square kilometre. It is actually about 89 hectares.

Learning about area helps us understand our world. It lets us compare a small park to a huge city. We can use it to plan where to build things. It even helps scientists plan big projects. For example, people want to build a radio telescope. This is called the Square Kilometre Array. It will be built in South Africa and Australia. It aims to have a collecting area of about 1 km2.

Dimensions of the old city of Delft
Dimensions of the old city of Delft

Measuring space helps us see how everything fits together.

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File:Caldey Island map 1952.jpg
Caldey Island map 1952.jpg
File:Dimensions of the old city of Delft.svg
Dimensions of the old city of Delft.svg
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