Some ground truth considerations in inland water quality surveys

Ground data requirements are more stringent and difficult in aerial water quality surveys than in land surveys, as a result of the dynamic nature of water quality as well as the complex energy-water interaction giving rise to noise components in the signal measured by the airborne sensor. This paper presents some of the considerations influencing the ground truth strategy adopted in recent NRSA (National Remote Sensing Agency) water quality studies. Various aspects such as depth of sampling, time-lags, location of sampling sites on remotely sensed data, elimination of spectral noise components and planning of redundancy in ground truth are addressed. Careful collection, preservation, storage and analysis of water samples can contribute significantly to reliable water quality mapping from aerial altitudes.