A method of dropping a plurality of probes intended to partially penetrate into a ground, to carry out measurements in the ground, the method comprising the following steps: - flying at least a probe carrier flying vehicle above a dropping area on the ground, the probe carrier flying vehicle carrying probes and a launching unit , able to separate each probe from the probe carrier flying vehicle ; - activating the launching unit to separate at least one of the probes from the probe carrier flying vehicle ; - at least partial insertion of the probe in the ground of the dropping area ; characterized by : - when the probe carrier flying vehicle is located above a target dropping area, before activating the launching unit , determining a vegetation information at the target dropping area using a flying vegetation detector , the flying vegetation detector being an optical detector; wherein determining a vegetation information comprises the flying vegetation detector sending an optical signal towards the ground, and measuring the intensity and/or wavelength of the reflected signal or measuring the reflection time of the signal, the vegetation information being a vegetation density, a vegetation type or a vegetation height; the method comprising preventing the activation of the launching unit when the vegetation information at the target dropping area is comprised in a first category of vegetation and/or allowing the activation of the launching unit when the vegetation information at the target dropping area is comprised in a second category of vegetation. - flying at least a probe carrier flying vehicle above a dropping area on the ground, the probe carrier flying vehicle carrying probes and a launching unit , able to separate each probe from the probe carrier flying vehicle ; - activating the launching unit to separate at least one of the probes from the probe carrier flying vehicle ; - at least partial insertion of the probe in the ground of the dropping area ; characterized by : - when the probe carrier flying vehicle is located above a target dropping area, before activating the launching unit , determining a vegetation information at the target dropping area using a flying vegetation detector , the flying vegetation detector being an optical detector; - when the probe carrier flying vehicle is located above a target dropping area, before activating the launching unit , determining a vegetation information at the target dropping area using a flying vegetation detector , the flying vegetation detector being an optical detector; wherein determining a vegetation information comprises the flying vegetation detector sending an optical signal towards the ground, and measuring the intensity and/or wavelength of the reflected signal or measuring the reflection time of the signal, the vegetation information being a vegetation density, a vegetation type or a vegetation height; the method comprising preventing the activation of the launching unit when the vegetation information at the target dropping area is comprised in a first category of vegetation and/or allowing the activation of the launching unit when the vegetation information at the target dropping area is comprised in a second category of vegetation. <EOS>