2), this is probably because the calibration settings of the MultiSPEC camera cannot be recognized by this software. Worth noting is the fact that the processing of the multispectral images with the Agisoft software resulted in misalignment errors (see Fig. The cameras were auto-calibrated by Agisoft except for the multiSPEC camera for which a field calibration was necessary prior to each flight, more specifically, a spectral field calibration, with the eMotion software, at the beginning of each flight during which a few pictures were taken at a 0.5–1 m from the ground. All images were aligned and rectified and a final orthomosaic of each flight was produced in the Greek Geodetic Reference System 1987 (GGRS87). Furthermore, all flights were based on waypoints and had a lateral overlap of 60% or 65% and a forward overlap of 75% or 80%.Īerial triangulation by bundle block adjustment for all images of each flight mission was performed with Agisoft Photoscan Professional (RGB and NIR flights) and Pix4D software (multiSPEC flights). The flight height for the RGB camera had a range from 115 to 170 m, for the NIR camera from 170 to 260 m, and for the MultiSPEC camera from 115 to 190 m. The format of the GCP was a black square of 15 cm × 15 cm in the center of a white background on an A3 sized paper (see Fig. Before the first flight eight GCP were positioned in good distribution and afterwards measured with the real time kinematic GNSS method they remained on the vineyard during the whole flight season. The climate variables during the flight season were high sunshine with temperatures from 8 to 26 ☌ and infrequent rainfalls (only 1 day of heavy rain (45.2 mm) in August and 21 small rainfalls below 10 mm during the rest of the season) contributing to the drought phenomenon. The first flight was conducted mid-March (after pruning) at approximately 1130 under clear sky conditions, as were the following flights (in a timespan from 1000 to 1200 hours in order not to have very different solar positions). Ces faits suggèrent que les instruments utilisés dans cette étude représentent une solution rapide, fiable et efficace pour l'évaluation de récolte au moyen d'applications dans le domaine agricole. En outre, les résultats finaux étaient à haute résolution pour des fins d'analyses dans le domaine agricole (une échelle de 1:500 pour les trois capteurs). Les indices de TCARI/OSAVI ont montré la meilleure corrélation avec les échantillons de raisins en ce qui a trait à la maturité et à la probabilité de stress hydrique. Des échantillons de raisins ont été recueillis deux jours avant la récolte puis analysés et mis en corrélation avec les indices provenant de la télédétection. Les images provenant de vols ont été traitées par photogrammétrie pour produire des orthoimages et ont ensuite servi à l'extraction d'indices pour la détection du stress hydrique. Quinze vols ont été effectués avec un UAV à voilure fixe au cours des mois d'avril à août 2015, et ce, avec un intervalle moyen de deux semaines. La zone d'étude est le vignoble de Gerovassiliou dans la région d'Epanomi en Grèce où l'on cultive le cépage local de Malagouzia. Le présent article porte sur la surveillance de vignobles aux fins de l'évaluation du stress hydrique et de la maturité des raisins, et ce, au moyen d'un véhicule aérien sans pilote (UAV) muni de caméras multispectrale, infrarouge ainsi que rouge-vert-bleu (RVB). These facts suggest that the instruments used in this study represent a fast, reliable, and efficient solution to the evaluation of crops for agricultural applications. Furthermore, the final results were of high resolution as far as farm purposes are concerned (a scale of 1:500 for all three sensors). The TCARI/OSAVI index showed the best correlation with the grape samples with regards to maturity and the likelihood of water stress. Grape samples were collected 2 days before harvest and then analyzed and correlated with remote sensing indices. The flight images were photogrammetrically processed for the production of orthoimages and then used to extract indices for the detection of water stress. Fifteen flights were conducted with a fixed-wing UAV during the months of April to August 2015 with a mean interval of 2 weeks. The study area is the Gerovassiliou winery in the region of Epanomi, Greece, cultivated with the local grape variety of Malagouzia. This paper deals with the monitoring of vineyards for the assessment of water stress and grape maturity using an unmanned aerial vehicle (UAV) equipped with multispectral/infrared and red-green-blue (RGB) cameras.
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