There are certain principles that address the ideas central to the practice of remote sensing, regardless ofspecific disciplinary applications. This is similar to viewing different colours, although remote sensing also deals with wave lengths outside the visible colour range. This principle forms the basis of multispectral remote sensing, the science of observing features at varied wavelengths to derive information about the features and their spatial distribution. Hence, different wavelengths highlight different characteristics of a feature. Remote sensing systems are either active or passive.
Every sensor has a limit to the size of the smallest area which can be resolved on an image.
This is often referred to as a sensor's resolution. The ability to interpret remotely sensed data depends largely on the image resolution. However, higher resolution is not always better as it significantly increases image file size and the greater detail can act as 'noise' during interpretation. It is always recommended that the complexity of the landscape, the detail required in the final product, and desired spectral bands be considered when choosing image data, rather than just resolution alone. Geometric correction Remotely sensed images are not planimetric maps because they contain geometric distortions introduced by the Earth's shape and rotation, the remote sensing platform's orbital and imaging instabilities, viewing geometry, and terrain relief displacement.