General Description

Remote Sensing is making measurements about an object without the instrument being in direct contact with the object. Eyesight for example, is a form of remote sensing. When the eye sees an object, the electromagnetic radiation (reflected light) from the surface of the object is registered and the contained information about the surface can be seen as colour.

Satellites are using sensors that work like our eyes. Important difference is that satellite images are not only from the visible region but from the whole electromagnetic spectrum. Satellites collect images from different parts of the earth and are continuously monitoring the earth from space.

Depending on the satellite sensor, images could be of high or low resolution. The satellite scanning procedure converts the area into a grid (Figure 1) according to the satellite spatial resolution. The spatial resolution specifies the pixel size of the satellite image (Figure 2). The smaller the pixel size, the better the spatial resolution, which results in a more detailed image.

There are many earth observation satellites active in space with different characteristics, enabling the use of satellite data in many applications of the scientific community. Apart from the scientific community, several public entities use satellite images for varying applications. For example military operations, disaster monitoring, infrastructure development planning and monitoring, etc.

Nowadays, more people are becoming familiar with satellite images as satellite remote sensing is used in everyday life. Characteristic examples are:

• Google Earth which uses satellite images in different spatial resolutions according to the population and density of each area.
• The weather forecasting report that uses satellite images to show weather fronts and forthcoming weather.