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Square kilometre

math Maturity 11-13 Next article →

A square kilometre is a unit used to measure area. Area describes the size of a flat surface. The square kilometre is a multiple of the square metre. The square metre is the standard SI unit for area. Scientists and map makers use the symbol km2 to represent this measurement. It is important to note that km2 means (km)2. It does not mean k(m2), which would be a kilo-square metre. This distinction is vital for accuracy in mathematics. For example, 3 km2 equals 3,000,000 m2, not 3,000 m2.

To understand the scale, we can look at different conversions. One square kilometre is exactly 1,000,000 square metres. It is also equal to 100 hectares. If you are using different systems, 1 km2 is approximately 0.3861 square miles. It is also about 247.1 acres. You can also look at it in reverse. One square metre is 0.000001 km2. One hectare is equal to 0.01 km2. These relationships help us translate measurements between various global systems.

Map makers use these units to create topographical map grids. These grids help people navigate large areas of land. On many maps, grid lines are placed at one-kilometre intervals. This creates squares that each represent one square kilometre. The physical size of these squares on paper changes based on the map scale. 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 creates a square with an area of 4 cm2. On a 1:25,000 map, the lines are 4 cm apart. This results in a square area of 16 cm2 on the paper.

Caldey Island map 1952
Caldey Island map 1952

History shows us that many medieval European cities were roughly this size. These cities often had large walls to protect the citizens. The area enclosed by these walls was frequently about one square kilometre. You can still see the history of these layouts in modern cities. In Brussels, a ring road now follows the path of the old wall. In Frankfurt, the old walls have been replaced by gardens. We can estimate these ancient areas by fitting them to shapes like rectangles or ovals.

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

Specific cities provide excellent examples of these historical measurements. The city of Delft in the Netherlands was approximately rectangular. Its dimensions were roughly 1.30 km by 0.75 km. This creates a perfect rectangle of about 0.9 km2. Lucca in Italy is another example with a roughly rectangular shape. Its maximum width is 1.36 km and its maximum height is 0.80 km. A perfect rectangle of these dimensions would be 1.088 km2. The city of Bruges in Belgium was shaped more like an oval or an ellipse. Its dimensions were 2.53 km by 1.81 km. This would result in an area of approximately 3.597 km2.

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

Other large spaces also fall near this measurement. Many parks are almost exactly one square kilometre in area. Examples include Riverside Country Park and Brierley Forest Park in the UK. In the US, Jones County Central Park in Iowa is a similar size. Even the Old City of Jerusalem is nearly one square kilometre. It actually measures about 89 hectares. Golf courses also frequently occupy this amount of space. An 18-hole course typically requires about 80 hectares, or 0.8 square kilometres. The Manchester Golf Club in the UK is an example of this size.

Understanding area allows us to connect different fields of study. It helps us move from simple geography to complex engineering. For instance, scientists use these measurements for massive telescopes. The Square Kilometre Array is a proposed radio telescope. It will be located in South Africa and Australia. This project intends to have a collecting area of approximately 1 km2. This shows how a single unit of measurement can support global scientific discovery.

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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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