An imaging method for imaging an area of terrain using a sensor mounted on an unmanned aircraft, the method comprising: acquiring, by one or more processors, a specification of possible positions and orientations relative to the aircraft to which the sensor may be moved; acquiring, by the one or more processors, positional information of the area of terrain; acquiring, by the one or more processors, a specification of the manoeuvrability of the aircraft; using the acquired specification of the possible positions and orientations of the sensor relative to the aircraft, the acquired positional information of the area of terrain, and the acquired specification of the manoeuvrability of the aircraft, determining, by the one or more processors, a first procedure and a second procedure; performing, by the aircraft, the first procedure, the first procedure comprising the aircraft moving with respect to the area of terrain along a first route and the sensor moving with respect to the aircraft such that, for each point in the area of terrain, that point is coincident with a footprint of the sensor on the ground for at least some time during the first procedure; whilst the aircraft performs the first procedure, capturing, by the sensor, a first set of images, each image in the first set being of only part of the area of terrain, the first set of images being such that, for every point in the area of terrain, that point is present within at least one of the images in the first set; thereafter, performing, by the aircraft, the second procedure, the second procedure comprising the aircraft moving with respect to the area of terrain along a second route and the sensor moving with respect to the aircraft such that, for each point in the area of terrain, that point is coincident with a footprint of the sensor on the ground for at least some time during the second procedure; and whilst the aircraft performs the second procedure, capturing, by the sensor, a second set of images, each image in the second set being of only part of the area of terrain, the second set of images being such that, for every point in the area of terrain, that point is present within at least one of the images in the second set; wherein the first route is different to the second route. acquiring, by one or more processors, a specification of possible positions and orientations relative to the aircraft to which the sensor may be moved; acquiring, by the one or more processors, positional information of the area of terrain; acquiring, by the one or more processors, a specification of the manoeuvrability of the aircraft; using the acquired specification of the possible positions and orientations of the sensor relative to the aircraft, the acquired positional information of the area of terrain, and the acquired specification of the manoeuvrability of the aircraft, determining, by the one or more processors, a first procedure and a second procedure; performing, by the aircraft, the first procedure, the first procedure comprising the aircraft moving with respect to the area of terrain along a first route and the sensor moving with respect to the aircraft such that, for each point in the area of terrain, that point is coincident with a footprint of the sensor on the ground for at least some time during the first procedure; whilst the aircraft performs the first procedure, capturing, by the sensor, a first set of images, each image in the first set being of only part of the area of terrain, the first set of images being such that, for every point in the area of terrain, that point is present within at least one of the images in the first set; thereafter, performing, by the aircraft, the second procedure, the second procedure comprising the aircraft moving with respect to the area of terrain along a second route and the sensor moving with respect to the aircraft such that, for each point in the area of terrain, that point is coincident with a footprint of the sensor on the ground for at least some time during the second procedure; and whilst the aircraft performs the second procedure, capturing, by the sensor, a second set of images, each image in the second set being of only part of the area of terrain, the second set of images being such that, for every point in the area of terrain, that point is present within at least one of the images in the second set; wherein the first route is different to the second route.