A drone comprising: - a vertical-view video camera, adapted to point towards a scene of the ground overflown by the drone, to capture a sequence of images of this scene and to deliver as an output a corresponding digital image signal ( S camV); - an inertial unit comprising gyrometric sensors adapted to measure the Euler angles ( φ, θ, ψ) characterising the attitude of the drone with respect to an absolute terrestrial reference system and to deliver as an output a gyrometric signal ( S gyro) representative of the instantaneous rotations of the drone; - rotation compensation means, receiving as an input i) the image signal ( S camV) delivered by the camera and ii) the gyrometric signal ( S gyro) delivered by the inertial unit, and delivering as an output readjusted image data, compensated for the rotations of the drone from one image to the following one; and - means for estimating the horizontal speeds of the drone based on the displacements from one image to the following one of the scene captured by the vertical-view camera, these estimation means receiving as an input said readjusted image data, characterized in that, the image signal and the gyrometric signal having a variable time offset between each other: - the vertical-view camera and the inertial unit are driven by a common clock; - the frequency of acquisition of the gyrometric sensors is a multiple of the frequency of delivery of the image signal of the vertical-view camera; and - it is further provided a circuit adapted, during the flight of the drone and in real time, to: • compare the synchronisation signal ( V sync_Gyro) of the gyrometric signal ( S gyro) delivered by the inertial unit with the synchronisation signal ( V sync_CamV) of the image signal ( S camV) delivered by the vertical-view camera; • determine a phase-shift value based on the time offset (Δ) between these respective synchronisation signals; • apply this phase-shift value at the input of the rotation compensation means; and - the rotation compensation means are further adapted to perform, before the computation of said readjusted image data, a previous correction of resynchronization of the image signal ( S camV) delivered by the vertical-view camera onto the gyrometric signal delivered by the inertial unit. - a vertical-view video camera, adapted to point towards a scene of the ground overflown by the drone, to capture a sequence of images of this scene and to deliver as an output a corresponding digital image signal ( S camV); - an inertial unit comprising gyrometric sensors adapted to measure the Euler angles ( φ, θ, ψ) characterising the attitude of the drone with respect to an absolute terrestrial reference system and to deliver as an output a gyrometric signal ( S gyro) representative of the instantaneous rotations of the drone; - rotation compensation means, receiving as an input i) the image signal ( S camV) delivered by the camera and ii) the gyrometric signal ( S gyro) delivered by the inertial unit, and delivering as an output readjusted image data, compensated for the rotations of the drone from one image to the following one; and - means for estimating the horizontal speeds of the drone based on the displacements from one image to the following one of the scene captured by the vertical-view camera, these estimation means receiving as an input said readjusted image data, - the vertical-view camera and the inertial unit are driven by a common clock; - the frequency of acquisition of the gyrometric sensors is a multiple of the frequency of delivery of the image signal of the vertical-view camera; and - it is further provided a circuit adapted, during the flight of the drone and in real time, to: • compare the synchronisation signal ( V sync_Gyro) of the gyrometric signal ( S gyro) delivered by the inertial unit with the synchronisation signal ( V sync_CamV) of the image signal ( S camV) delivered by the vertical-view camera; • determine a phase-shift value based on the time offset (Δ) between these respective synchronisation signals; • apply this phase-shift value at the input of the rotation compensation means; and • compare the synchronisation signal ( V sync_Gyro) of the gyrometric signal ( S gyro) delivered by the inertial unit with the synchronisation signal ( V sync_CamV) of the image signal ( S camV) delivered by the vertical-view camera; • determine a phase-shift value based on the time offset (Δ) between these respective synchronisation signals; • apply this phase-shift value at the input of the rotation compensation means; and - the rotation compensation means are further adapted to perform, before the computation of said readjusted image data, a previous correction of resynchronization of the image signal ( S camV) delivered by the vertical-view camera onto the gyrometric signal delivered by the inertial unit.