Fixed point photography as a hydromorphology monitoring tool

Abstract

[EN] Assessing and monitoring river areas is necessary to support river management and restoration processes. As rivers change over short periods of time assessment methods need to be quick, reliable and cost/time-effective. Fixed point photography has potential, but some challenges remain. A methodology has been developed in order to obtain useful information from sets of multitemporal images. First, the images are registered to a common coordinate system, both automatic and manual methodologies were developed. Second, vegetation and water features were extracted. Vegetation coverage can be obtained using a combination of Green Leaf Algorithm (GLA) and texture characteristics. Water presence-absence is derived from the images using a combination of different clues, such as hue, saturation, brightness, texture and ground detection techniques. The extracted features allow the evaluation of changes over time. However, the accuracy of the results is limited by the differences in image conditions; such as illumination, orientation, and point of view location. Another important limitation is water correct segmentation, which remains an important challenge in RGB images. Therefore, some improvements to current photo-based monitoring programs are proposed, such as the use of stereo or NIR images, or measures to allow the photographs to be taken from the same exact location every time.

[ES] El proyecto busca investigar cómo podría aplicarse la fotografía de punto fijo para la creación de una línea temporal que muestre los cambios en los ríos desde el punto de vista ecológico y geomorfológico. Se deberán identificar las variables a extraer de las fotografías mediante la revisión de la literatura reciente (ej. Cobertura vegetal, tipo de vegetación, anchura del cauce, sedimento, profundidad del cauce) y desarrollar una metodología para ello de forma tan automatizada como sea posible. El proyecto se realizará en colaboración con la Agencia Medioambiental de Reino Unido (Environment Agency) y se utilizarán las fotografías del programa Springs to Source . Estas imágenes son tomadas mensualmente y pueden complementarse con información de otras fuentes, como estaciones de aforo, si se considera necesario.