ABSTRACT
Low resolution remotely sensed environmental data usually correspond to images with a spatial resolution greater than 1 km but often have a pixel size of several kilometers. As those images cover extended geographical areas and provide reasonable temporal frequencies for environmental monitoring, they are regarded as essential parts for operational environmental monitoring while a major advantage is the low cost per unit of surveyed area. Vegetation performance, soil conditions, drought monitoring, flood potential, and terrestrial water storage are among the numerous applications of low resolution remotely sensed products at the regional, continental, or global scale. For detailed environmental studies at the local scale, input from low resolution imagery is used as auxiliary information along with high resolution products and ground measurements to downscale the spatial resolution to the required scale. Although when dealing with remotely sensed missions, the detection of radiation comes to mind, this is not always the case. Therefore, within this chapter we will focus on two major approaches in low resolution remote sensing; the first, which does not measure reflected radiation from Earth, is related to the determination of anomalies of Earth’s gravitational field, while in the second approach soil moisture content is monitored using measurements at the microwave wavelength.
