Colour aerial photographs of the Waitemata Harbour, Auckland were scanned at a resolution of 300 dots per inch using a green filter. Ninety in situ water samples were collected at 0.3 m deep during the period when the photographs were being taken, and were used to derive suspended solids concentration (SSC) in a laboratory. The mosaiced photographs were resampled from 1 m to 5 m and 10 m resolutions. The total mass of suspended solids was estimated from the image and the bathymetric data in a GIS. It was found that there is a linear, close relation between SSC and its reflectance on the scanned photographs. The regressed relation has the largest R2 value at 10m. The total mass of suspended solids is estimated at 1401 tons. The main factor affecting the accuracy of estimation is the inconsistency in the tone of the photographs used.