What is remote sensing?


Envisat (Artist's view)
 
 
 
 
Remote sensing is a way of collecting and analysing data to get information about an object without the instrument used to collect the data being in direct contact with the object.
 
For example, if you take a photograph of your house, and on the picture you see that the house is composed of a roof, walls and windows, all of which appear as different colours, then this is remote sensing.

In remote sensing, three elements are essential. They are:

1 - a platform to hold the instrument
2 - a target object to be observed
3 - an instrument or a sensor to observe the target

For example, when you take a photograph of your house, you are the platform, the photographic emulsion of the film inside the camera is the sensor and the house is the target object.

A key additional element, and the main purpose of remote sensing systems, is:

4 - the information that is obtained from the acquired data, and how it is used and stored
 
 
 In the example of the photograph of your house, the information obtained is all you can identify about the house from the photograph. Examples could be the colour of the shutters, a hole in the roof, and an open window.

Can you think of another example combining the four important elements involved in remote sensing?

* See the bottom of the page for the answer
  
 
 When Earth scientists talk about remote sensing, the observed object is the Earth. In general terms then, remote sensing is a tool to observe and study the Earth, its land surface, the oceans, the atmosphere and its dynamics from space.

For scientists, the platforms are all means used to be 'at a distance' from the Earth's surface, such as planes and satellites. The target is our planet itself, the sensors are contained in all the instruments used to observe the Earth (cameras, scanners, radars, etc) and finally the information obtained is everything that increases our knowledge about our planet, such as cloud cover over Europe, the evolution of the ozone hole, the spreading of the deserts, the progress of deforestation, and much more.

Note: From now on, when the term remote sensing is used, it will be in the sense used by Earth scientists. Remote sensing is a technology that primarily aims to observe and study the Earth system, the environment and its dynamics.
 
 
 Conclusion
  
If you have understood this introduction to remote sensing and were able to answer all the questions, then you already have a good basis to start interpreting satellite images. There are, however, still many things to discover. You can improve your knowledge by visiting the rest of the Eduspace website. You will then learn more about different satellites orbiting around our planet and their applications. Eduspace will also provide you with satellite images you can download and use. To do so, a software package called LEOworks has been made available. You can download it from the website too. Finally, several exercises will take you through satellite imagery interpretation.

If this introduction was a little too complex and you still have questions, read through the pages again. If there are still things that aren't clear to you, ask your teachers, who might be able to help you. Alternatively, do not hesitate to send us your questions at the following address: eduspace @ esa.int
 
 
 * Answer: A microscope:
Platform = table;
Object = observed cells;
Sensor = microscope;
Information = all that is seen and interpreted.

Try this exercise with a telescope, CCTV, a radar speed camera on the side of a road and try to think of others...

 
 
  
Last update: 19 January 2010


Elements of remote sensing

 •  Platforms (http://www.esa.int/SPECIALS/Eduspace_EN/SEM2BR3Z2OF_0.html)
 •  Observed objects (http://www.esa.int/SPECIALS/Eduspace_EN/SEM3CR3Z2OF_0.html)
 •  Sensors (http://www.esa.int/SPECIALS/Eduspace_EN/SEM4GR3Z2OF_0.html)
 •  The information contained in an image (http://www.esa.int/SPECIALS/Eduspace_EN/SEM4HR3Z2OF_0.html)