SVS synthetic visual display method based on OSG and OSGEarth

Abstract

The invention discloses an SVS synthetic view display method based on OSG and OSGEarth, and the method comprises the steps: employing an OSGEarth three-dimensional simulation engine, loading the terrain elevation and texture image data in real time according to the pose information of an airplane and the view field information of a camera, and generating a virtual synthetic view; on the basis of the synthetic scene, an electronic flight instrument and a safe flight channel are overlaid and used for displaying the flight state and guidance information. According to the SVS synthetic visual display method based on the OSG and the OSGEarth, rapid construction of a virtual scene can be achieved, and therefore clear cabin external scenes and flight guide information are provided for pilots. According to the invention, even under the condition of low visibility, a pilot can obtain more key information, and the flight safety guarantee is obviously enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of computer simulation, and in particular to an SVS synthetic vision display method based on OSG and OSGEarth. Background Art

[0002] With the rapid development of civil aviation, the safety of aircraft in low visibility conditions has become increasingly prominent. Despite the availability of a variety of advanced ground and airborne navigation equipment, low visibility is still the main factor leading to controlled flight into terrain and runway incursion accidents. Therefore, in order to improve flight safety and reduce the pilot's flight load and aircraft costs, synthetic vision systems (SVS) have emerged. As an important part of the electronic flight instrument system, SVS provides real-time simulation and enhanced display of the external environment by combining external sensor data with information from the internal database. This integrated and intuitive display technology enables pilots to obtain clearer flight information in complex and low-visibility environments, thereby effectively reducing flight risks and improving flight safety. Therefore, this paper constructs a synthetic vision display system based on OSG and OSGEarth combined with the air safety flight corridor model. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an SVS synthetic vision display method based on OSG and OSGEarth, which can realize an accurate virtual flight environment and provide more key information for pilots.

[0004] In order to solve the above technical problems, the present invention provides an SVS synthetic vision display method based on OSG and OSGEarth, including: using the elevation information database of the airport model and its surrounding terrain to simulate the three-dimensional terrain; using real-time flight status information to draw intuitive flight information; using pre-planned route information to draw the flight corridor.

[0005] Preferably, a method for displaying a SVS synthetic vision based on OSG and OSGEarth, wherein the specific steps of displaying a virtual synthetic vision are as follows:

[0006] Step 1: Use the 30m-precision earth elevation information and pyramid-style satellite images to write earth files based on OSGEarth to generate a three-dimensional digital earth.

[0007] Accordingly, in step 1, XML is used to write earth files to mark geospatial data. When using TMS driver; define the elevation layer <elevation>When using the GDAL driver, define the ocean layer <oscean>When using the Triton driver.

[0008] Step 2: Use the airport model and its longitude and latitude coordinates to add the airport to the three-dimensional digital map.

[0009] Correspondingly, in step 2, the computeLocalToWorldTransformFromLatLongHeight function in the OSG library is used to obtain the transformation matrix of the airport model from the latitude, longitude and height to the world coordinate system, and then the model is added to the world coordinate system after obtaining the model.

[0010] Step 3: Use the flight attitude and position information to set the camera to roam along the path to simulate the first-person perspective of the aircraft.

[0011] Correspondingly, in step three, after receiving the flight data, the AnimationPathManipulator fixed path roaming method is used to simulate the first-person perspective during flight.

[0012] Preferably, in an SVS synthetic vision display method based on OSG and OSGEarth, the information displayed by the electronic flight instrument includes: 1) longitude 2) latitude 3) altitude 4) speed 5) vertical speed 6) pitch angle 7) roll angle 8) heading angle. The longitude, latitude, and vertical speed are displayed in text, and the altitude, speed, and attitude angle are displayed in controls.

[0013] Preferably, in an SVS synthetic vision display method based on OSG and OSGEarth, the mathematical model of the safe flight channel is:

[0014] The safe flight channel is centered on the trajectory predicted by the current flight state and constructed with the uncertainty of the aircraft position at each epoch as the boundary. The three-dimensional positioning error is decomposed into horizontal and vertical directions. Among them, the uncertainty of the horizontal position error H PL The calculation formula is:

[0015] H PL =K H σ m (1)

[0016] In the formula, K is the amplification factor, and its calculation formula is:

[0017]

[0018] f ratio =σ m / σ n

[0019]

[0020] Among them, σ m and σ n are the major and minor semi-axes of the 1σ error ellipse, respectively. They correspond to the variance of the horizontal x-direction position error, the variance of the horizontal y-direction position error, and the covariance between the x- and y-direction position errors.

[0021] The uncertainty calculation formula of vertical position error is:

[0022] V PL =K v σ z (3)

[0023] In the formula, K V =5.33 is the expansion coefficient in the vertical direction, σ z is the standard deviation of the vertical z-direction position error.

[0024] Preferably, a SVS synthetic vision display method based on OSG and OSGEarth, and a projection model construction method for a safe flight channel:

[0025] The coordinates of a point p in the geodetic coordinate system, i.e. the longitude and latitude coordinates, are known. e p p =[L p λ p h p ] T , it needs to be converted to the geographic coordinate system, that is, the northeast celestial coordinate g p p =[x g y g z g ] T , and then further converted to the coordinates in the body coordinate system b p p =[x b y b z b ] T Next, convert it to the camera coordinate system c p p =[x c y c z c ] T However, since the display screen is a two-dimensional coordinate system, it needs to be converted to a two-dimensional image coordinate system. i p p =[u p v p 1] T Finally, since the image coordinate system and the pixel coordinate system are in the same plane, the coordinate axes are parallel to each other and have the same direction, but the coordinate origins are different, it is necessary to convert to the pixel coordinate system. p p p =[r p c p 1] T , so that it can finally be displayed on the display.

[0026] The beneficial effects of the present invention are: it can realize the rapid construction of virtual scenes, thereby providing pilots with clear cabin external scenes and flight guidance information. Through the present invention, even in low visibility conditions, pilots can obtain more key information, significantly enhancing flight safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the SVS synthetic vision display effect diagram based on OSG and OSGEarth.

[0028] Figure 2 This is an illustration of the SVS synthetic view control based on OSG and OSGEarth.

[0029] Figure 3 Display renderings for safe flight channels. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] like Figure 1 As shown, the method adopts the OSGEarth three-dimensional simulation engine to load terrain elevation and texture image data in real time according to the aircraft's posture information and camera field of view information, thereby generating a virtual synthetic vision, and superimposing electronic flight instruments and safe flight channels to display flight status and guidance information.

[0032] Specifically, a method for displaying a virtual synthetic scene using an SVS based on OSG and OSGEarth includes the following specific steps for displaying a virtual synthetic scene:

[0033] Step 1: Use 30m accurate earth elevation information and pyramid-style satellite images to write earth files based on OSGEarth to generate a 3D digital earth. Use XML language to write earth files to mark geospatial data. When using TMS driver; define the elevation layer <elevation>When using the GDAL driver, define the ocean layer <oscean>When using the Triton driver.

[0034] Step 2: Use the airport model and its latitude, longitude and height coordinates to add the airport to the 3D digital map. Use the computeLocalToWorldTransformFromLat LongHeight function in the OSG library to obtain the transformation matrix of the airport model from the latitude, longitude and height to the world coordinate system, and then add the model to the world coordinate system after obtaining the model.

[0035] Step 3: Use the flight attitude and position information to set the camera to roam along the path to simulate the first-person perspective of the aircraft. After receiving the flight data, use the AnimationPathManipulator fixed path roaming method to simulate the first-person perspective during flight.

[0036] Specifically, an SVS synthetic vision display method based on OSG and OSGEarth, wherein the information displayed by the electronic flight instrument is as follows: Figure 2 shown.

[0037] Specifically, a SVS synthetic vision display method based on OSG and OSGEarth, the effect diagram of its safe flight channel is as follows: Figure 3 As shown, the mathematical model is:

[0038] The safe flight channel is centered on the trajectory predicted by the current flight state and constructed with the uncertainty of the aircraft position at each epoch as the boundary. The three-dimensional positioning error is decomposed into horizontal and vertical directions. Among them, the uncertainty of the horizontal position error H PL The calculation formula is:

[0039] H PL =K H σ m (1)

[0040] In the formula, K is the amplification factor, and its calculation formula is:

[0041]

[0042] f ratio =σ m / σ n

[0043]

[0044] Among them, σ m and σ n are the major and minor semi-axes of the 1σ error ellipse, respectively. They correspond to the variance of the horizontal x-direction position error, the variance of the horizontal y-direction position error, and the covariance between the x- and y-direction position errors.

[0045] The uncertainty calculation formula of vertical position error is:

[0046] V PL =K v σ z (3)

[0047] In the formula, K V =5.33 is the expansion coefficient in the vertical direction, σ z is the standard deviation of the vertical z-direction position error.

[0048] Specifically, a SVS synthetic vision display method based on OSG and OSGEarth, a specific projection method of the safe flight channel from three-dimensional coordinates to two-dimensional coordinates:

[0049] Coordinate definition: The geographic coordinate system takes the center of mass of the aircraft at takeoff as the origin. g =[L g λ g h g ] T , X g The Y axis points east along the latitude line. g The axis points north along the meridian, Z g The axis points to the sky along the normal line; the body coordinate system takes the center of mass of the aircraft at the current moment as the origin o b =[L b λ b h b ] T , X b The axis points to the right side of the body, Y b Axis points to the nose, Z b The axis passes through xy and is determined by the right-hand rule; the camera coordinate system, with the origin o c At the camera optical center, according to the right-hand rule: X c The Z axis points to the right of the camera. c The Y axis points to the front of the camera along the optical axis. c The axis is in the center plane of the lens and points upward; the image coordinate system defines the coordinates of the image on the CCD plane. The origin is the focus of the image plane, and the X i The axis is parallel to the direction of the scan line, Y i The axis is perpendicular to the scan line direction; the origin of the pixel coordinate system is located in the upper left corner of the image, the r axis is parallel to the scan line direction, and the c axis is perpendicular to the scan line direction.

[0050] 1) Geodetic coordinate system ==> Geographical coordinate system

[0051] A point on the known runway plane e p p The geodetic coordinate system [L p λ p h p ] T , respectively longitude, latitude and altitude, convert them to a point in the geographic coordinate system g p p =[x g y g z g ] T , the transformation relationship is:

[0052]

[0053] Where Rn is the radius of curvature of the meridian circle, and Rm is the radius of curvature of the meridian circle.

[0054] 2) Geographic coordinate system ==> body coordinate system

[0055] First find the geographic coordinates of the aircraft's center of mass:

[0056]

[0057] The body coordinates of point p are:

[0058]

[0059] in is the rotation matrix projected from the geographic coordinate system to the body coordinate system, It is the translation matrix projecting the geographic coordinate system to the body coordinate system.

[0060]

[0061] Among them, ψ, θ, and γ are the current heading angle, pitch angle, and roll angle of the aircraft respectively.

[0062] 3) Body coordinate system ==> camera coordinate system

[0063] The aircraft body and the camera are rigidly connected.

[0064]

[0065] in

[0066]

[0067] The distance between the camera optical center and the body mass center is l ab To simplify the model, we assume ab =0, that is, the origin of the camera coordinate system coincides with the origin of the body coordinate system.

[0068] 4) Camera coordinate system ==> Image coordinate system

[0069] Through the pinhole imaging model, the point in the camera coordinate system c p p =[x c y c z c ] T Transform to the next point in the image coordinate system i p p =[u p v p 1] T , in the flight approach scenario, the object distance is much greater than the focal length. The camera imaging model is as follows:

[0070]

[0071] 5) Image coordinate system ==> pixel coordinate system

[0072] The image coordinate system and the pixel coordinate system are in the same plane, the coordinate axes are parallel to each other and have the same direction, but the coordinate origins are different. i The coordinates in the pixel coordinate system are (u0, v0), the physical size of each pixel in the u-axis and v-axis directions is 1 / α and 1 / β, and the tilt factor is s, then any point in the image i p p =[u p v p 1] T Homogeneous coordinates projected in pixel coordinate system The expression is

[0073]

[0074] Finally, through a series of transformations, the projection coordinates of a point p in the three-dimensional map on the display are obtained.< / oscean> < / elevation> < / oscean> < / elevation>

Claims

1. A method for displaying SVS synthetic scenes based on OSG and OSGEarth, characterized in that: This method uses the OSGEarth 3D simulation engine to load terrain elevation and texture image data in real time according to the aircraft's posture information and camera field of view information, thereby generating a virtual synthetic vision and superimposing electronic flight instruments and safe flight channels to display flight status and guidance information.

2. The method for displaying SVS synthetic views based on OSG and OSGEarth according to claim 1, characterized in that: The specific steps of virtual synthetic vision display are: Step 1: Use 30m accurate earth elevation information and pyramid-style satellite images to write earth files based on OSGEarth to generate a three-dimensional digital earth; Step 2: Use the airport model and its longitude and latitude coordinates to add the airport to the three-dimensional digital map; Step 3: Use the flight attitude and position information to set the camera to roam along the path to simulate the first-person perspective of the aircraft.

3. The method for displaying SVS synthetic scenes based on OSG and OSGEarth according to claim 1, characterized in that The information displayed by the electronic flight instruments and the display methods are shown in the following table. Table 1 Electronic flight instrument display information and mode 4. The method for displaying SVS synthetic scenes based on OSG and OSGEarth according to claim 1, characterized in that The mathematical model and display method of the safe flight channel are as follows: The safe flight channel is centered on the trajectory predicted by the current flight state and constructed with the uncertainty of the aircraft position at each epoch as the boundary. The three-dimensional positioning error is decomposed into horizontal and vertical directions. Among them, the uncertainty of the horizontal position error H PL The calculation formula is: H PL =K H s m (1) In the formula, K is the amplification factor, and its calculation formula is: f ratio =s m / s n Among them, σ m and σ n are the major and minor semi-axes of the 1σ error ellipse, respectively. They correspond to the variance of the horizontal x-direction position error, the variance of the horizontal y-direction position error, and the covariance between the x- and y-direction position errors. The uncertainty calculation formula of vertical position error is: V PL =K v s z (3) In the formula, K V =5.33 is the expansion coefficient in the vertical direction, σ z is the standard deviation of the vertical z-direction position error. After the specific location and range of the safe flight channel are determined, the longitude and latitude coordinates of each part of the channel are calculated and converted into two-dimensional coordinates on the display. The steps of constructing the projection model are: earth coordinate system ==> geographic coordinate system ==> aircraft coordinate system ==> camera coordinate system ==> image coordinate system ==> pixel coordinate system.

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