Method for accurately geolocating an image sensor installed on board an aircraft
First Claim
1. A method for geolocating an image sensor having a line of sight and installed on board an aircraft, characterized in that the geographical position of the sensor and the orientation of its a line of sight being approximate, it comprises:
- 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 line of sight of the image sensor;
the operator moving the line of sight 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 delivered by a device 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 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; and
the operator pointing to this observable element in the displayed terrain image, the geographical coordinates pointed to being retrieved from the terrain database, this observable stationary element that the line of sight is tracking thus becoming an opportune landmark; and
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 a plurality of measurements of the distance between the sensor and the opportune landmark and with a plurality of measurements of the orientation of the line of sight of the sensor toward the opportune landmark, there being one orientation measurement for each telemetry measurement, simultaneously allowing the orientation of the line of sight to be accurately estimated.
1 Assignment
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Accused Products
Abstract
A method for geolocating an image sensor having an LoS and installed on board an aircraft. The geographical position of the sensor and the orientation of its LoS being approximate, it comprises: a step of creating an opportune landmark comprising the following substeps: an operator locating, on a screen for displaying acquired images, a stationary element on the ground, the axis of a telemeter being indicated in these images by means of a reticle the direction of which represents the LoS; the operator moving the LoS in order to place the reticle on this stationary element; tracking of this stationary element; estimating the approximate geographical position of this stationary element; searching in a terrain DB for the location corresponding to a zone centered on the stationary element; displaying an image of the terrain of this location, the operator locating the stationary element; and the operator pointing to this stationary element in the displayed terrain image, the geographical coordinates pointed to being retrieved from the terrain DB, this stationary element becoming an opportune landmark; and the sensor moving relative to the landmark, a step of accurately locating the sensor, from the geographical coordinates of this landmark and using a Kalman filter supplied with a plurality of measurements of the distance between the sensor and the landmark and with a plurality of measurements of the orientation of the LoS of the sensor toward the landmark, there being one orientation measurement for each telemetry measurement, simultaneously allowing the orientation of the LoS to be accurately estimated.
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Citations
11 Claims
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1. A method for geolocating an image sensor having a line of sight and installed on board an aircraft, characterized in that the geographical position of the sensor and the orientation of its a line of sight being approximate, it comprises:
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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 line of sight of the image sensor;the operator moving the line of sight 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 delivered by a device 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 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; and the operator pointing to this observable element in the displayed terrain image, the geographical coordinates pointed to being retrieved from the terrain database, this observable stationary element that the line of sight is tracking thus becoming an opportune landmark; and 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 a plurality of measurements of the distance between the sensor and the opportune landmark and with a plurality of measurements of the orientation of the line of sight of the sensor toward the opportune landmark, there being one orientation measurement for each telemetry measurement, simultaneously allowing the orientation of the line of sight to be accurately estimated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification