1. A method for estimating the speed of movement of a first video camera at the moment at which that first video camera captures a current image of a three-dimensional scene, the current image including pixels organized in parallel rows, the rows of pixels having been captured one after the other so that a non-zero time t Δ elapses between the moments of capture of two successive rows of the current image, this method including: a) storing in an electronic memory a reference image corresponding to an image of the same scene captured by a second video camera in a different pose, the reference image including pixels organized in parallel rows, the memory containing for each pixel of the reference image the measurement of a physical magnitude measured by that pixel, that physical magnitude being chosen in the group made up of the intensity of radiation emitted by the point photographed by that pixel and a depth separating that pixel from the point of the scene photographed by that pixel, b) storing in the electronic memory the current image, the memory containing for each pixel of the current image the measurement of a physical magnitude measured by that pixel, that physical magnitude being the same as the physical magnitude measured by the pixels of the reference image, c) storing in the electronic memory for each pixel of the reference image or of the current image the measurement of a depth that separates that pixel from the point of the scene photographed by that pixel, d) estimating the pose x pR of the first video camera, e) estimating the speed x vR of movement of the first video camera during the capture of the current image, wherein the step e) is executed by seeking the speed x vR that minimizes, for N points of the reference image, where N is an integer greater than 10% of the number of pixels of the reference image, a difference directly between: a first value of the physical magnitude at the level of a first point of the reference image, that first value being constructed from at least one measurement of that physical magnitude stored in that reference image, and a second value of the same physical magnitude at the level of a second point of the current image, that second value being constructed from measurements of that physical magnitude stored in the current image and the coordinates of the second point, the coordinates of the second point in the plane of the current image being obtained: by determining the coordinates of a third point in the plane of the current image that corresponds to the projection onto that plane of the point of the scene photographed by the first point, those coordinates being determined from the estimated pose x pR and the measurements of the depths stored in the current image or the reference image, then by shifting the third point a distance equal and opposite to the distance traveled by the first video camera between a time t 1 at which a first row of the current image is captured and a time t i at which the row of pixels to which the third point belongs was captured, that distance being a function of the time t Δ and the speed x vR , and finally by projecting the third point shifted in this way onto the plane of the current image to obtain the coordinates of the second point.