A method for geolocating an image sensor having a line of sight, LDV and installed on board an aircraft, the geographical position of the sensor and the orientation of its LDV being approximate, the method comprising: - a step of creating at least one opportune landmark comprising the following substeps: ❖ an operator locating, on a screen for displaying acquired images, an observable stationary element on the ground, the axis of a telemeter being indicated in these images by means of a "reticle" type overlay the direction of which in the scene space represents the LDV of the image sensor; ❖ the operator moving the LDV in order to place the reticle marking the axis of the telemeter on this stationary observable element; ❖ tracking of this stationary element by tracking means; ❖ estimating the geographical position of this stationary element from image capture conditions, CPDV, delivered by a device (7, 8) able to determine them, this position also being approximate; ❖ on the basis of the approximate position of this tracked stationary element, searching in a terrain database, BD terrain, for the location corresponding to a zone centered on the approximately positioned stationary element, this zone being of preset size; ❖ displaying an image of the terrain of this location, said image being constructed from the terrain database, the operator locating the observable element in this image; ❖ the operator pointing to this observable element in the displayed terrain image (91, 91'), the geographical coordinates pointed to being retrieved from the terrain database, this observable stationary element that the LDV is tracking thus becoming an opportune landmark; - the sensor moving relative to the opportune landmark, a step of determining the accurate location of the sensor, from the geographical coordinates of this tracked opportune landmark, using a Kalman filter supplied with several measurements of distances between the sensor and the opportune landmark and with several measurements of the orientation of the LDV of the sensor toward the opportune landmark, there being one orientation measurement for each telemetry measurement, simultaneously allowing the orientation of the LDV to be accurately estimated. - a step of creating at least one opportune landmark comprising the following substeps: ❖ an operator locating, on a screen for displaying acquired images, an observable stationary element on the ground, the axis of a telemeter being indicated in these images by means of a "reticle" type overlay the direction of which in the scene space represents the LDV of the image sensor; ❖ the operator moving the LDV in order to place the reticle marking the axis of the telemeter on this stationary observable element; ❖ tracking of this stationary element by tracking means; ❖ estimating the geographical position of this stationary element from image capture conditions, CPDV, delivered by a device (7, 8) able to determine them, this position also being approximate; ❖ on the basis of the approximate position of this tracked stationary element, searching in a terrain database, BD terrain, for the location corresponding to a zone centered on the approximately positioned stationary element, this zone being of preset size; ❖ displaying an image of the terrain of this location, said image being constructed from the terrain database, the operator locating the observable element in this image; ❖ the operator pointing to this observable element in the displayed terrain image (91, 91'), the geographical coordinates pointed to being retrieved from the terrain database, this observable stationary element that the LDV is tracking thus becoming an opportune landmark; ❖ an operator locating, on a screen for displaying acquired images, an observable stationary element on the ground, the axis of a telemeter being indicated in these images by means of a "reticle" type overlay the direction of which in the scene space represents the LDV of the image sensor; ❖ the operator moving the LDV in order to place the reticle marking the axis of the telemeter on this stationary observable element; ❖ tracking of this stationary element by tracking means; ❖ estimating the geographical position of this stationary element from image capture conditions, CPDV, delivered by a device (7, 8) able to determine them, this position also being approximate; ❖ on the basis of the approximate position of this tracked stationary element, searching in a terrain database, BD terrain, for the location corresponding to a zone centered on the approximately positioned stationary element, this zone being of preset size; ❖ displaying an image of the terrain of this location, said image being constructed from the terrain database, the operator locating the observable element in this image; ❖ the operator pointing to this observable element in the displayed terrain image (91, 91'), the geographical coordinates pointed to being retrieved from the terrain database, this observable stationary element that the LDV is tracking thus becoming an opportune landmark; - the sensor moving relative to the opportune landmark, a step of determining the accurate location of the sensor, from the geographical coordinates of this tracked opportune landmark, using a Kalman filter supplied with several measurements of distances between the sensor and the opportune landmark and with several measurements of the orientation of the LDV of the sensor toward the opportune landmark, there being one orientation measurement for each telemetry measurement, simultaneously allowing the orientation of the LDV to be accurately estimated.