Using digital cameras for river plume and water quality measurements

The results from a pilot study in coastal waters off the east coast of Ireland using both an in situ and airborne mounted digital camera are described. In situ digital pictures are significantly affected by sea surface reflection. This can be eliminated with the use of a hollow pipe, attached to the camera lens, which intersects the sea surface such that a picture of light upwelled from beneath the surface is obtained. Used in this way, linear relations between both the ratio of red/green digital output (O/P) values (at a particular camera exposure) and the difference in green–red digital camera O/P were found with mineral suspended solid (MSS) concentration. A good comparison was also found between the ratios of red/green upwelling light measured with the camera and a conventional irradiance sensor. Semi‐empirical or analytical relationships between camera O/P and the inherent optical properties of the water could not be established, however. This was probably due, in part, to a lack of range in values f...