Satellite images

 

Satellite imagery 

Satellites

A satellite is an artificial moon. It is a machine launched in to space that orbits the earth, another planet or a star!

Moon is earth’s natural satellite and earth is one of Sun’s natural satellites!!!

Satellites differ in size and shape. A satellite has an antenna and a power source.

They are used for many different purposes.

Soviet Union was the first country to launch a satellite in to space in 1957. It was Sputnik 1. One year later in 1958 NASA launched America’s first satellite, Explorer 1.

Most satellites are taken in to space on rockets and are set in their orbits.

There are two types of orbits:

1.     Geostationary orbits – a satellite set on a geostationary orbit is called a geostationary satellite. They move over the Equator from west to east.

They travel at the same speed as that of the rotation of earth. Therefore they appear stationary above the same location.

 

2.     Polar orbits – A satellite that moves from Pole to Pole are called a polar satellite that moves on a polar orbit.  Since the earth spins from west to east and as they travel from pole to pole above earth, they scan many places on earth.

 

Uses of satellites

1.     To forecast weather

2.     For communications

3.     For navigation

4.     Locate  areas of mineral ores and oil reserves

5.     To assess disaster damages

6.     To forecast about impending disasters

7.     To identify damaged vegetation

8.     To make maps

 

Satellite images can cover an enormous area at once and this is a clear advantage over aerial photos.

Satellite pictures are of two types:

1.     True colour satellite imagery

2.     False colour satellite imagery

 

True colour satellite images

The features are shown in their real colours as they appear to our unaided eye.

For example: water bodies appear in blue, ice – white, forests and vegetation – green, deserts – yellow/tan/ light brown

 

(The colours are sometimes slightly enhanced on the same hues for clarity)

 Applications/ Uses of true colour satellite images:

1.     Cartography (map making)

2.     To easily identify physical and human features

Drawbacks

1.     Can be only captured during daylight

2.     Not suitable to identify subtle terrain features

3.     Difficulty in distinguishing between clouds and snow

False colour satellite images

The features on the image do not appear in the normal colours that we see them in real life. The colours are made fake and are not real. Hence the name false colour.

 

Some common uses of false colour satellite images

1.     These images are used to identify subtle features which would not otherwise be distinguishable by the unaided eye.

2.     Also used to locate damaged crop patches within large fields.

3.     To identify temperature variations (thermal bands)

Disadvantages

1.     They are complicated

2.     Needs a key to identify features

By Kanchana Wickramasinghe