Algorithm for turbidity mapping using digital camera images from a low-altitude light aircraft

Due to high cost and difficulty in obtaining cloud-free satellite images in the equatorial region, new techniques are invented and introduced. Besides that, in situ measurements are accurate but slow, costly, and difficult in adverse weather conditions. In this study, high spatial resolution digital airborne images were captured by a conventional digital camera and used for turbidity mapping. Turbidity distribution in river and coastal waters can be measured with optical remote sensing instruments. High-altitude aerial photography provides an effective method of monitoring the dynamics of turbidity concentration in Penang Island, Malaysia. The objective of this study is to evaluate the feasibility of using a digital camera to provide useful data for the turbidity mapping studies. The digital images were captured from a low-altitude flying aircraft. Turbidity measurements were collected simultaneously with the airborne image acquisition. The measurements locations were determined using a handheld GPS. The images were separated into three bands (red, green and blue) for multispectral analysis. The digital numbers for each band corresponding to the sea-truth locations were extracted and were used for calibration of the water quality algorithm. The algorithm used is based on the reflectance model, which is a function of the inherent optical properties of water that can be related to the concentration of its constituents. The proposed algorithm shows higher R and low RMS values. Finally, the turbidity map was generated using the proposed algorithm. This finding shows that digital camera has the potential to supply useful data for turbidity studies over a small study area.