III - WHAT IS A DIGITAL IMAGE?
2- CHARACTERISTICS OF AN IMAGE
Remote sensing images are often classified based on a number of characteristics arising from the combination of the sensors used, the platforms and the trajectory or flight parameters.
We distinguish four main properties of images:
- spectral resolution
- spatial resolution
- temporal resolution
- radiometric resolution.
Spectral resolution refers to the number and width of intervals of the electromagnetic spectrum used, spatial resolution to the ground area of a pixel, temporal resolution to the repetition of observations over time and radiometric resolution to the detail with which electromagnetic energy is recorded. They are described in this chapter.
Developing a sensor that simultaneously gives the highest performance for all four parameters for all possible applications is utopian for the time being. Better performance in one area generally leads to poorer results in the other. Of course, cost also plays an important role in the development of a sensor. It is therefore important to make choices when setting up an earth observation programme and to accept that not all parameters are optimal.