Methods and devices for obtaining a geographical coordinate for a position on the ground

A processing device for obtaining a geographical coordinate for a position on the ground, said processing device comprising:

• at least one processor arranged to:
• determine an initial pose of a video camera on-board an aerial platform, wherein the initial pose is determined from at least three identified visual points in a first image of the ground obtained using said on-board video camera and corresponding visual points from a textured 3D geo-referenced model of the environment;
• continuously determine a pose of the video camera on-board the aerial platform starting from the determined initial pose and from continuously updated video camera images and the textured 3D model of the environment;
• receive a request for determining a geographical coordinate for a position on the ground, said request comprising a second image from the continuously updated video images in which second image a location of the position on the ground is indicated;
• and
• determine the geographical coordinate of the indicated position on the ground based on a determined pose of the video camera on-board the aerial platform at the time of capture the second image, based on the second image and based on the textured 3D model of the environment.