A large part of the work of WaterWatch is based on spatial information derived from satellites: remote sensing. Basically remote sensing is the collection of information of an object or phenomenon by the use of a device that is not in physical or intimate contact with the object. Remote sensing has evolved to one of the most powerful scientific disciplines for providing operational tools and products for water resources management.

Earth observation satellites have a wide range of applications. Weather satellites such as MSG and GOES observe the earth's weather and climate. Other earth observation satellites provide information on the land cover (change) and satellites with a high spatial resolution even make it possible to distinguish the crop type. Some satellites provide surface temperature. Another specific earth observation data set is the SRTM Digital Elevation Model, which has not been acquired by a satellite but by Space Shuttle mission.

For the selection of satellite data the costs and the resolution have to be considered:

• spatial resolution: determines the level of detail visible;
• spectral resolution: determines the information available; and
• temporal resolution: how often is new information acquired.