Object-based Analysis and Multispectral Low-altitude Remote Sensing for Low-cost Mapping of Chalk Stream Macrophytes

Their small size and high biodiversity have until now made UK chalk streams unsuitable subjects for study with remote sensing techniques. Future technological developments are however likely to change this. The study described in this paper shows how high resolution multispectral images taken with an off-the-shelve, infrared sensitive digital camera, can give a first insight into future opportunities for mapping and monitoring of submerged chalk stream environments. The high resolution multispectral images have been used in combination with Object Based Image Analysis (OBIA) techniques to map submerged vegetation. Preliminary results show that the Near Infrared Red information recorded by the camera greatly improves the classification of individual macrophyte species. The benefit of the object-based image analysis approach is at the presented stage only limited, but a first attempt at creating a robust rule set has been applied to photos taken at two different field sites with some success. The analysis also showed how texture features are useful for the separability between macrophyte classes. Overall the results are promising for further applications of remote sensing techniques to chalk streams as well as for application of the low cost sensor set-up.