MONITORING SPATIAL BEHAVIOR OF PASTORALIST SHEEP THROUGH GPS, LIDAR DATA AND VNIR IMAGE

Abstract. Global Navigation Satellite Systems (GNSS), such as the Global Position System (GPS), are currently used to replace the traditional pastoralism and to remotely control the movements and location of the herds. Besides, the use of this remote monitoring can benefit the understanding of grazing resource use and livestock management. In this work we investigated the herd behaviour in a Spanish organic farm of free pastoralist sheep with a joint use of different geodata sources. The area of study comprised approximately 900 hectares with a variety of land covers dedicated to pasture. A herd of 300 head was monitored during 2009 and 2010. GPS data were acquired every 5 minutes. In addition, a comprehensive map of land uses/land covers (LU/LC) was retrieved through a supervised classification of a mosaic of orthophotographs (visible and near infrared bands, VNIR). Then, the digital elevation model (DEM) and the digital surface model (DSM) were obtained from a 2010 LiDAR (light detection and ranging) campaign, which allowed the retrieval of terrain attributes and vegetation parameters. The positioning and behaviour of the GPS-tracked sheep were analysed in terms of the retrieved topographic characteristics and land uses. The study of the most influential variables indicated that the slope and aspect were the topographic attributes that most exerted impact on the grazing activity, being the north direction the most preferable, as well as a gentle slope. Regarding the LU/LC, grassland areas were selected by the sheep, specifically in areas of short vegetation (i.e., outside shrublands and trees beyond 0.5 m high).