Remote sensing is by USGS defined as “Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area”.

In addition to this definition there are two key concepts we need to mention at this point namely:

1. The sensors  or instrument i.e. the mechanism by which the amount of radiation (Electro Magnetic Radiation or EMR) is measured. The most common type of sensor is a multispectral radiometer so named because the measure the EMR at multiple different wavelengths.
2. The platform  is the device that caries the sensor over the target. Common platforms are drones, airplanes and not least satellites.