LSPIV vs Mini Secchi

LSPIV (large-scale particle image velocimetry) is an image-based method for measuring velocity distribution on the water surface. Applications of LSPIV have been increasing for both field and laboratory experiments as unique and powerful tools for non-intrusive velocimetry using conventional imaging devices and specialized image processing software. This app utilizes a smartphone to implement LSPIV. By innovatively combining the sensors embedded in smartphones, the images captured with them can be intrinsically and instantly ortho-rectified without making recourse to GCPs. The app was developed under support by the River Fund in charge of the Foundation of River and Watershed Environment Management (FOREM), Japan; Grant-in-Aid for Young Scientists (B); and the Research Fund of Japan Institute of Country-ology and Engineering.

The Secchi disk is a white disk that is lowered into the water and the depth at which it disappears and reappears from sight is logged. This depth is proportional to the clarity or transparency of the water. The Forel Ule colour scale is used to classify the colour of natural waters.It consists of 21 colours ranging from blue to green to yellow to brown, and is used alongside the Secchi disk with the observer typically recording the colour of a submerged Secchi disk with this app. The app will guide you through each measurement, store location data, photos and additional observations.