The invention relates to the field of aircraft guidance. It more particularly relates to an automatic method of guiding an aircraft such as a drone a position remote from an airport to landing of the aircraft on a runway of the airport. STATE OF THE ART Guidance systems existing drones possible to produce a self-guiding an unmanned along a predetermined path, for example corresponding to the path of an observation mission. To produce such a guide, the position of the aircraft is determined at regular intervals and compared with the path to be followed. This position is generally determined using a receiver of an absolute positioning satellite system, such as GPS or Galileo. It may however happen that the aircraft's computer is unable to determine the current position of the aircraft, or because of a failure of a component of the aircraft, such as a GPS receiver or because of an unavailability of the positioning system signal, for example in case of jamming thereof. Without knowing the position of the aircraft, the processor thereof is then unable to guide the aircraft to make it follow the predetermined path. The aircraft guidance system is then particularly unable to send it to its intended landing point such as an airport runway. The aircraft then risk crashing in an unknown position and be lost. To avoid this, the current position of the aircraft can be determined using another system board by the latter. For example, the calculator the aircraft can determine the position from signals supplied by the inertial unit of the aircraft continuously measuring linear and angular accelerations of the aircraft. Integration of the signals supplied by the inertial unit to determine the movements of the aircraft and thus determine its position relative to the last position supplied by the satellite positioning system. However, determining the position of the aircraft with such a method based on the integration of the inertial signals may have a high uncertainty. Accumulated over time gaps between the movement determined by integration and the actual movement of the aircraft causes a drift in the position of the aircraft determined in relation to its actual position. Such drift can reach several kilometers per flight hour since the last position received through the satellite positioning system. In the case of a satellite positioning failure occurring at a long distance from the landing expected point and resulting in guidance of the aircraft from the signals of the inertial unit for a long time, the guidance system may, of Due to this drift, drive without knowing the aircraft at a position remote from several kilometers from the landing point. The aircraft will be unable to know its actual position, to find the airport planned for the landing and to land. There is therefore a need for a guide method to safely guide an aircraft, independently, from a point of return to a distant airport and land the aircraft on a track of it, despite the unavailability of satellite positioning and despite a pronounced drift of the current position of the aircraft determined from the signals of the inertial unit. PRESENTATION OF THE INVENTION The present invention relates in a first aspect to an automatic assistance method for landing an aircraft on a runway landing from a point of return to a point of completion at which the aircraft comes into contact with the runway, said method being implemented by a data processing device on board said aircraft and configured to be connected to: - an inertial measurement unit configured to estimate the position and attitude of the aircraft, - an altimeter configured to measure the altitude of the aircraft, - a distance measuring device configured to measure relative to a reference point the azimuth of the aircraft relative to a reference direction, said method being characterized in that it comprises: - a phase of assistance to return navigation comprising the guide, from position and attitude data supplied by the inertial unit and an altitude data provided by the altimeter of the aircraft along a predefined trajectory the point of return to a predetermined hooked point approximately aligned with the axis of the runway, the guide being formed on at least a portion of said predetermined path from corrected position data calculated using position data of the aircraft provided by the inertial unit and of measurements transmitted by the distance measuring device, -a phase of assistance landing comprising guiding the aircraft to the point of the hooked end point. The measures passed by the possible deviation measurement to correct the position of the central inertial data to compensate for the drift of it. The aircraft can thus be brought to the point of hanging C with reduced uncertainty to land it safely. The phase of assistance for return shipping may include: - a first of the aircraft guiding step along the predetermined path from the point of return to a predetermined point of capture, from position and attitude data supplied by the inertial unit and altitude data provided by the altimeter, - a second step of guiding the aircraft along the predetermined path of the capture point at the point of hanging from attitude data supplied by the inertial unit, elevation data provided by the altimeter and corrected position data calculated using aircraft position data supplied by the inertial unit and azimuth measurements transmitted by the distance measuring device, said predefined path requiring the aircraft between the capture point and the B point of hanging a turning movement. The turning movement implemented from the point of capture and hanging point reduces the uncertainty of the position of the aircraft related to uncertainties and measurement bias in the distance measuring device. The aircraft can thus be guided to the point of hooked with increased accuracy ensuring proper alignment of the aircraft with the runway. The first step of guiding the boost phase to return navigation may include the guidance of the aircraft along the predetermined path of the return point to capture point from attitude data supplied by the central inertial, altitude data provided by the altimeter and corrected position data calculated using aircraft position data supplied by the inertial unit and azimuth measurements transmitted by the distance measuring device. Measurements of the distance measuring device can thus be used to compensate for drift of the inertial unit from the return point, minimizing the uncertainty in the position of the aircraft during the guidance thereof to the capture point. In a first implementation variant, the pre-set path between the return point and the capture point is straight. A straight path minimizes the distance between the return point and the capture point, minimizing the return time and the consumption of resources on this portion of the return path. In a second implementation variant, the pre-set path between the return point and the point of capture is zigzag. A zigzag path makes it possible to further vary the angular variation range measured by the distance measuring device and thus reduce the uncertainty and uncertainty about the position of the aircraft. The data processing device being configured to be also connected to a camera on board the aircraft, the landing assistance phase may comprise estimating a position of the end point in an image of the airstrip captured by the camera and estimating a position of the aircraft as a function of said position of the estimated finishing point in the image and altitude data provided by the altimeter. The aircraft position can thus be determined throughout the landing with a lower uncertainty than if it was determined by the inertial unit and or distance measuring. This increased precision helps guide aircraft safely between the point of hanging and the culmination and land it. The data processing device being further configured to be connected to a transceiver on board said aircraft for receiving signals from at least three transceivers positioned on the ground, the landing assistance phase can include position data corrected estimate of the aircraft from position data provided by the inertial unit, azimuth measurements transmitted by the distance measuring device, data of distances between the board and said transceiver in three transceivers on the ground. The use of distance information between the aircraft and fixed points on the ground in a known position as the transceivers to the ground reduces the uncertainty of the position of the aircraft determined from the inertial unit and the distance measuring device in order to accurately guide the aircraft to the point of culmination. According to a second aspect, the invention relates to a computer program product comprising code instructions for executing the method according to the first aspect when said program is executed by a processor. According to a third aspect, the invention relates to a data processing device configured to implement the support method of the first aspect. According to a fourth aspect, the invention concerns an automatic system to assist the landing of an aircraft on a runway comprising: - an inertial measurement unit configured to estimate the position and attitude of the aircraft, - an altimeter configured to measure the altitude of the aircraft, - a distance measuring device configured to measure relative to a reference point the azimuth of the aircraft relative to a reference direction, -The data processing device according to the third aspect. Said assist system according to the fourth aspect may further include a camera configured to be connected to the data processing device. Said assistance system of the fourth aspect may further comprise: - at least three transceivers positioned on the ground; -a transceiver for receiving signals transmitted by said at least three transceivers positioned on the ground, on board said aircraft and configured to be connected to the data processing device. Such computer program products, data processing devices and systems have the same advantages as those mentioned for the method of the first aspect. PRESENTATION DES FIGURES Other features and advantages will become apparent from reading the following description of an embodiment. This description will be given with reference to the accompanying drawings in which: 1 schematically illustrates an example of guiding the landing of an aircraft on a runway from a return point A to a point PA result according an implementation mode of the invention; 2 illustrates a support system to the landing of an aircraft according to an embodiment of the invention; Figure 3 illustrates the two radio links connecting the data processing device to a ground station as well as the distance measuring device included in the assistance system for the landing of the invention; 4 shows a landing assistance system for an aircraft according to an embodiment of the invention; FIG 5 is a diagram diagrammatically showing an example of implementation of the automatic method for assisting the landing of an aircraft according to the invention; FIG 6 is a diagram illustrating the calculation of corrected position data from measurements transmitted by the distance measuring device according to an implementation mode of the invention; Figure 7 is a diagram showing diagrammatically the difference between the position of the aircraft and the point of hooked at the end of turning movement of the aircraft as a function of radius of curvature; Figure 8 illustrates the landing assistance phase according to the invention when the support system is equipped with a camera; 9 illustrates the positioning of a reticle in an image on the endpoint; FIG 10 is a diagram illustrating the calculation of corrected position data from measurements transmitted by the distance measuring device according to an implementation mode of the invention. DETAILED DESCRIPTION An embodiment of the invention relates to an automatic method for assisting in the landing of an aircraft 1 on a runway from a return point A to a PA culmination point at which the aircraft comes into contact with the runway, as shown in Figure 1. This method is implemented by a data processing device 2 of a support system for landing 3, as shown in Figure 2. the assistance landing system 3 may also comprise a 4 altimeter and an inertial unit 5 installed on board of the aircraft and to which the data processing device can be connected. The altimeter 4 may be a barometric altimeter or a laser altimeter. The pressure altimeter may be accurate to 10 meters and can be repositioned with the value of the atmospheric pressure QNH which is the barometric pressure corrected for instrumental errors, temperature and gravity and brought by means sea level (MSL or Mean Sea Level). In practice, the QNH pressure may be given with reference to the threshold of the runway, so that the altimeter shows the geographical altitude PA culmination point when the aircraft is on the runway threshold in question . The laser altimeter can be accurate to 0.2 meters and be used when the altitude is less than 100 meters. 5 the inertial unit is able to integrate the movements of the aircraft (acceleration and angular velocity) to estimate the orientation (angles of roll, pitch and heading), its linear velocity and position. It includes accelerometers for measuring the linear accelerations of the aircraft in three orthogonal directions and gyros to measure the three components of the vector angular velocity (roll speeds, pitch and yaw). The IMU also provides the attitude of the aircraft (roll angle, pitch and heading). This process offers guided safely an aircraft such as a drone or an airliner, independently, from a remote point back to the airstrip, for example that of an airport, and landing the aircraft on the runway, despite the unavailability of the positioning satellite and despite a pronounced drift of the current position of the aircraft determined by its inertial unit 5, by correcting the position data provided by the control panel using additional position data provided by a ground system. For this, the data processing device 2 is capable of being loaded on the device and may include a computer and a communication interface. Such on-board computer may be a processor or microprocessor, type x-86 or RISC e.g., a controller or microcontroller, a DSP, an integrated circuit such as an ASIC or programmable such as a FPGA, a combination of such elements or any other combination of components to implement the calculation steps of the method described below. Such a communication interface may be any interface, analogue or digital, enabling the computer to exchange information with the other elements of the support system 3 such that the altimeter 4 and the inertial unit 5. Such an interface can for example be an RS232 serial interface, USB, Firewire, HDMI, or Ethernet network interface. As shown in Figure 2, the computer 2 of the data processing device may be shared between an autonomous navigation system 6 and a flight control system (VCS) 7. The autonomous navigation system 6 may be responsible for estimating the latitude and longitude of the position of the aircraft and the altitude during the landing. The flight control system 7 can be instructed to conduct the guidance of the aircraft as a function of latitude data and longitude provided by the autonomous navigation system 6, altitude provided by the altimeter and 4 of the aircraft attitude data such as heading, roll and pitch, 5 supplied by the inertial unit. for this, the flight control system can transmit instructions to the aircraft control units such as electrical, hydraulic or hybrid actuators operating the rudders 8 or the throttle 9. 2 the data processing device can be connected to a ground station, usually placed near the airport or airstrip, via two connections as shown in Figure 3: -a link 1 1, called "control / command" bidirectional radio and C2 in a band of the electromagnetic spectrum between 3 and 6 GHz, which allows the exchange of command and control messages between the ground station and the aircraft. The transmitted signals are modulated with a single carrier modulation and are transmitted / received with an omnidirectional antenna mounted on a mast head at the ground station; -a job data link 12M and bidirectional radio in a band between 10 and 15 GHz of the electromagnetic spectrum which enables the exchange of data flows generated by the various vehicle sensors. The transmitted signals are modulated using a multi-carrier modulation and are transmitted / received with a directional antenna such as a parabola, masthead mounted. The landing assistance system 3 also comprises a distance measuring device 13. Such a distance measuring device is a system ground and connected to the directional antenna of the ground station used for the data link assignment 12. The distance measuring device is configured to continuously measure the direction in which the aircraft is located, i.e. the azimuth of the aircraft relative to a reference direction, such as north. The azimuth of the aircraft is measured with respect to a reference point, for example with respect to the position of the directional antenna mounted masthead. The distance measuring device can measure the angle from the orientation of the directional antenna provided by an antenna positioner electromechanical device configured to position in azimuth and elevation directional antenna to point it to the aircraft for maximize the quality of the radio link. The distance measuring device is configured to transmit the azimuth measurement data to the data processing device via the link control / control 1 1. The method proposes to use these azimuth data transmitted by the distance measuring device and of the aircraft position data supplied by the inertial unit to calculate corrected position data compensating for the drift of the inertial unit. These corrected position data can be used to guide the aircraft to a point C hooked predetermined approximately aligned with the axis of the runway and located in periphery of a hooked point centered area PA and predetermined radius result, as shown in Figure 1. For example, such a gripping zone may have a radius less than or equal to 5 km. The landing assistance system 3 may also comprise an additional positioning system dedicated to the guidance of the aircraft in the bonding during a landing phase until the end point area. In a first embodiment shown in Figure 2, the landing assistance system 3 includes a board camera 14 on board the aircraft on which the data processing device can be connected. Such a camera may be an infrared camera pans e.g. type SWIR ( "Shortwave Infrared Range", of wavelength between 0.9 and 1 .7 microns). The video stream acquired by the camera is transmitted firstly to the processing device 2 so as to identify the runway and determine the position of the aircraft with respect thereto upon landing, and the other to the ground station by means of the mission data link. In a second embodiment shown in Figure 4, the landing assistance system 3 includes at least three transceivers positioned and onboard transceiver 15 of the aircraft and configured to be connected to the data processing device 2. Such transceivers may be of radio tags UWB (Ultra Wide Band). By exchanging signals with the transceivers on the ground, the on-board transceiver is capable of determining the distance separating it from each of the transceivers on the ground, for example by measuring the transmission time of a round-trip signal. The on-board transceiver is also configured to transmit these distances to the processing device 2. Knowing the positions of the transceivers to the ground, the processing device 2 can determine a corrected position of the aircraft from the data of azimuth transmitted by the distance measuring device, the position of the aircraft data provided by the inertial unit and the distance data provided by the on-board transceiver. The process steps are described in more detail in the following paragraphs, referring to Figure 5. The method may include a phase support to return navigation P1 during which the processing device carries out route guidance, from position and attitude data supplied by the inertial unit 5 and altitude data provided by 4 altimeter of the aircraft along a predetermined trajectory of the return point a to the point C hooked predetermined approximately aligned with the axis of the runway. To compensate for the drift of the position data supplied by the inertial unit, the guide may be performed on at least a portion of said predetermined path from corrected position data calculated using aircraft position data provided by the inertial unit and measures submitted by the distance measuring device. Alternatively, the corrected position data can also be calculated based on altitude data provided by the altimeter. The method may also include a phase of assistance landing P2 during which the processing device carries out the guidance of the aircraft hanging from C point to PA culmination point. Calculating the corrected position data involving measurements transmitted by the distance measuring device can be achieved by a minimization module 16 minimizing a cost function as shown in Figure 6. Such a cost function may be a mathematical expression includes terms of power difference between the actual position coordinates of the aircraft and the corresponding coordinates supplied by the inertial navigation system or the distance measuring device. These ratings can be arbitrarily chosen or selected so as to modulate or increase the relative importance of each contribution with respect to the other. The desired corrected position coordinates are then selected coordinates as real position coordinates minimizing the cost function according to the criterion of the least "powers". An example of a simple cost function C does not take into account the altitude measurements from the altimeter is provided below. This cost function includes a term for example C1 based on the position data determined by the inertial unit and a C2-term function of the azimuth measurement provided by the distance measuring device. C (x (t), y (t)) = C ^ xjQ. YCT)) + C 2 (x (, y (Q) distance measuring inertial Determining the position of the aircraft being performed discretely, it is assumed in this example that it is carried out periodically with a sampling period T. It is up to time t = kT. Or : (X (mT), y (mT)): retaining position of the aircraft at the instant mT. (X ^ y ^ mT mT)): Position data by the inertial unit at time mT. 5 ^ axi (mT): maximum drift of the inertial unit at time mT. p. q: Optional parameters to gradually comply with the cost function to a "rectangular well" (when p, q → ∞). θ (ηιΤ): Azimuth retained the aircraft relative to the reference direction at time mT. 0 e (mT) measured azimuth of the aircraft relative to the reference direction at time mT. : Standard deviation of the measurement error committed by the distance measuring device The angle 6 (t) is related to the coordinates (x (t), y (t)) as follows: 0(t) = arg(x(t) + iy(t)) = Re(-i log(x(t) + iy(t))) where Re denotes the real part. The powers p, q may be adjusted to vary the weight of each term in the function C according to the current guiding step, for example so as to reduce the importance of once inertial point B capture past. C1 and C2 terms exemplified are based on the position data and azimuth measurements provided several instants mT prior to the time kT to which the corrected position data x (t), y (t) are sought. The position coordinates (x (mT), y (mT)), (x ^ y ^ ^ mT mT)) and measures azimuth 6 (mT), 0 e (mT) having already been determined or measured for the prior times t = kT, these terms are assumed to be known for m