Method and device for determining the absolute pose of a camera located on board an aircraft or spacecraft

A real-time method for determining an absolute pose of a camera in a reference coordinate system, said camera being monocular and passive and being located on board an aircraft or spacecraft that is able to move relative to a scene known and mapped in the form of a reference three-dimensional (3D) model, wherein the method comprises:

• obtaining a sequence of at least two successive images captured by the camera at respective successive times, each image comprising a plurality of pixels, each pixel of an image partially representing the scene viewed by the camera at the time of capture of said image,
• determining, from the sequence of images, a local 3D model in a coordinate system that is centered and oriented relative to the camera, said local 3D model representing a portion of the scene in three dimensions corresponding to the capture of an image, referred to as target image, among the sequence of images, the determination of the local 3D model comprising a dense matching of all pixels of the target image with pixels of other images among said sequence,
• providing an approximate absolute pose of the camera,
• determining the absolute pose of the camera at the time of capture of the target image, by realigning the position and attitude of the local 3D model with the reference 3D model, the position and attitude realignment being carried out in a search domain, based on the approximate absolute pose of the camera.