Assessing land-use in olive groves from aerial photographs

This work aims to determine variations in cover crop, bare soil and tree areas in olive (Olea europaea L.) groves as affected by the season based on aerial photographs and estimated vegetation indexes. Conventional-colour and colour-infrared aerial photographs were taken in spring and summer on three olive farms of 75–100 ha, from a plane at 1525 m above the ground. Images (scale 1:10,000) were digitized, georeferenced and processed. Twenty-six selected vegetation indexes were assayed for land-use discrimination. Early summer was the most suitable time to distinguish between cover crops and olive trees. Conventional-colour was more adequate and economic than infrared photography. Indexes based on blue and red wavelength reflectivity values divided by combinations of several reflectivity values were suitable for cover crop and olive tree discrimination. Selected vegetation indexes allowed for the cover crop areas to be estimated at 32.50% of the 100.5 ha total farm surface, with an estimated accuracy of 91.9±1.4%.