The Ngongotaha river UDPS experiment: low-cost underwater dynamic stereo photogrammetry

We propose to integrate the newest developments in stereomatching theory, affordable parallel processing capabilities (using GPU e.g. PC gaming/graphic card) and statistical surface analysis to implement and test an in-situ Underwater Dynamic Stereo Photogrammetry (UDSP) system for civil engineering applications. The proposed UDPS system aims to provide underwater Digital Elevation Models (DEM), for applications such as a two-dimensional discrete matrix of data underwater elevations. Experiments on river bed stereophotogrammetry in the Ngongotaha Stream near Rotorua using consumer grade stereo cameras including Go-Pro and Fujifilm W3 are used in through-water and underwater calibration and stereo measurements of 32 pebbles on the river bed. Pebbles are measured and identified. Initial results highlight the need for specialised equipment for through-water and underwater photogrammetry experiments to limit blurring effects caused by the water-plastic-air interfaces. Despite poor optical quality of the images obtained, we were able to correlate pebble sizes from calibrated stereo depth maps and actual measurement.