A method for determining corrections for artillery fire toward a fixed target using a fixed optronic geographical positioning observation system which can be oriented, and is equipped with a device for measuring the orientation of the line of sight thereof, a laser rangefinder, system positioning means, a display screen provided with a fixed central crosshair and harmonized with the axis of the rangefinder, means for displaying and moving a second crosshair on the screen, which method includes the following steps: - orienting the observation system so as to display the central crosshair on the image of the target on the display screen, - actuating the rangefinder to obtain the distance between the optronic system and the target, and - calculating geographical coordinates of the target as a function of the distance between the optronic system and the target provided by the rangefinder, the orientation provided by device for measuring the line of sight, and the position of the optronic system provided by the positioning means, characterized in that, in the event that, after firing, the impact of this firing and the target do not coincide, it includes the following steps: - the orientation of the system being fixed: ∘ displaying on the display screen the second crosshair on the image of the point of impact of the firing and measuring on the display screen the offset between the first and the second crosshairs (R1, R2), ∘ displaying a third crosshair on the display screen at a position that is symmetrical to that of the second crosshair relative to the first crosshair, - orienting the optronic system in order to position the third crosshair on the image of the target, the first crosshair then coinciding with the image of the impact point of the firing, - actuating the rangefinder in order to obtain the distance between the optronic system and the point of impact of the firing, - determining the distance between the target and the point of impact of the firing from the position of the optronic system provided by the positioning means, the offset between the first and the second crosshair (R1, R2) measured on the display screen, the distance between the optronic system and the target and the distance between the optronic system and the target and the distance between the optronic system and the point of impact of the firing. - orienting the observation system so as to display the central crosshair on the image of the target on the display screen, - actuating the rangefinder to obtain the distance between the optronic system and the target, and - calculating geographical coordinates of the target as a function of the distance between the optronic system and the target provided by the rangefinder, the orientation provided by device for measuring the line of sight, and the position of the optronic system provided by the positioning means, - the orientation of the system being fixed: ∘ displaying on the display screen the second crosshair on the image of the point of impact of the firing and measuring on the display screen the offset between the first and the second crosshairs (R1, R2), ∘ displaying a third crosshair on the display screen at a position that is symmetrical to that of the second crosshair relative to the first crosshair, ∘ displaying on the display screen the second crosshair on the image of the point of impact of the firing and measuring on the display screen the offset between the first and the second crosshairs (R1, R2), ∘ displaying a third crosshair on the display screen at a position that is symmetrical to that of the second crosshair relative to the first crosshair, - orienting the optronic system in order to position the third crosshair on the image of the target, the first crosshair then coinciding with the image of the impact point of the firing, - actuating the rangefinder in order to obtain the distance between the optronic system and the point of impact of the firing, - determining the distance between the target and the point of impact of the firing from the position of the optronic system provided by the positioning means, the offset between the first and the second crosshair (R1, R2) measured on the display screen, the distance between the optronic system and the target and the distance between the optronic system and the target and the distance between the optronic system and the point of impact of the firing.