CN108226873A - A kind of radar return display methods under android system - Google Patents

Abstract

The invention discloses the radar return display methods under a kind of android system.First, the mapping table from polar coordinates to rectangular co-ordinate and two equal-sized texture buffers are built in memory.Then, the part refreshed at a high speed update is not needed to by radar image upper position circle, away from mark circle, stem line etc. on a texture buffer.Secondly, the echo data of radar antenna is received and parsed through out, while the frame data are stored in echo buffering area, and with another texture buffer of the data update in buffering area.Finally, it is displayed on the screen by OpenGL mapping technologies and the rendering of multitexture hybrid technology.The division of teaching contents of radar asorbing paint is two display layers in android system by the present invention, and each display layer content independently refreshes, and improves rendering efficiency, while independent of specific hardware.

Description

A radar echo display method under Android system

technical field

The invention relates to the field of navigation and navigation, in particular to a method for displaying radar video images.

Background technique

Ship navigation radar is used to detect various objects such as icebergs, reefs, ships, and ice floes on the sea surface, and can provide effective target azimuth and distance information, so that ships can avoid various obstacles and prevent collision accidents. Necessary navigation equipment for sailing. The main features of the modern shipborne navigation radar display system are digital information processing, efficient information display, and easy-to-use human-computer interaction. Most of the implementation methods are System on Chip (SOC) platform or ARM (Advanced RISC Machines ) as the core embedded platform. As an important bridge between the radar operator and the radar system, the radar display and control terminal has many functions such as the drawing of radar video images, the identification and tracking of targets, and the display of ship information, providing important navigation information.

There are mainly three existing methods for displaying radar echoes: one is to use the original view framework to develop the display and control interface in the Qt development environment, and combine the FrameBuffer (frame buffer) technology to operate the video memory to draw the radar video image. The second is to use Graphical User Interface (GUI) technology to develop the radar display and control interface, combined with the graphics interface supporting hardware acceleration technology to complete the drawing of radar video images. The third is to use digital signal processing (Digital Signal Processor, DSP) or ARM processor to analyze the raw radar data and combine the radar video data of the baseband signal board to fuse the image data of the two for display. The first two methods have additional requirements on hardware, requiring GPU to support hardware acceleration or Alpha blending rendering; the third method has complex hardware design and is difficult to maintain and upgrade. In addition, the human-computer interaction experience of the display and control terminal developed by the above method is poor.

Contents of the invention

The purpose of the present invention is to solve the defects of the above three methods, provide a radar echo display method under the Android system, expand the application platform of radar display and control, and realize the efficient rendering of radar images based on OpenGL technology. The radar echo display method under a kind of Android system of the present invention comprises the following steps:

Step 1: Construct a mapping table T from polar coordinates to rectangular coordinates in memory. Described step one comprises two sub-steps:

Step 1 (1), for each point (x ₁ , y ₁ ) in the screen, calculate its corresponding polar coordinates, and put the mapping relationship of this point from polar coordinates to rectangular coordinates into table L;

Step 1 (2), traversing table L, storing the mapping relation of angle and radius as key and corresponding Cartesian coordinates as value in new data table T;

Step 2: Create two 2D texture buffers F and B of equal size.

Step 3. Update the azimuth circle, range marker circle, and bow line in F in the form of points.

Step 4: Receive and analyze the echo data of the radar antenna, and store the frame data into the echo buffer.

Step 5. Update B with the data in the echo buffer. This step contains four substeps:

Step five (1), check whether the cumulative echo angle difference in the echo buffer is greater than or equal to a given split angle, if not, then end step five;

Step 5 (2): Obtain the last two frames of data D ₁ and D ₂ stored in the echo buffer, obtain the echo data E and the starting angle θ ₁ from D ₂ , and obtain the ending angle θ ₂ from D ₁ ;

Step 5 (3), for each point on the screen whose angle is greater than or equal to θ ₁ and less than θ ₂ , find its Cartesian coordinates in T, and update in B with data E;

Step five (four), remove D ₁ and D ₂ from the echo buffer.

Step 6. Using OpenGL texture mapping technology in Android to render the radar echo image. This step contains six substeps:

Step 6 (1), create a GLSurfaceView and a custom View object and a Renderer object inherited from GLSurfaceView.Renderer in Android, and set the rendering mode to dirty rendering;

Step 6 (2), initialize the viewport through the function gl.glViewport(0,0,width,height). Where width is the screen width and height is the screen height;

Step 6 (3), initialize the frustum through the function gl.glFrustumf(left, right, bottom, top, zNear, zFar), left is -0.5×width, right is 0.5×width, bottom is -0.5×height, top is 0.5×height, zNear is 3, zFar is 7;

Step six (four), set the projection mode through the function gl.glMatrixMode(GL10.GL_MODELVIEW). Then clear the color buffer and load the identity matrix;

Step 6 (5), create two textures through the function gl.glGenTextures(2,ts,0), and associate them with F and B respectively, where ts is an array storing the number of texture objects;

Step 6 (6), enable the texture blending function through the function gl.glEnable(GL10.GL_BLEND), and set the texture blending mode through the function gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE_MINUS_SRC_ALPHA);

Step six (seven), bind the texture through the function gl.glBindTexture;

Step six (eight), update the texture with the data in B and F through the function gl.glTexSubImage2D;

Step six (nine), request the system to render the screen through the function requestRender.

Beneficial effect

The present invention proposes a method for displaying radar echoes under the Android system. The display of radar echo images is performed by creating a texture buffer on the memory to simulate video memory, and using OpenGL's multi-texture technology to simulate multiple layers. Compared with the traditional radar echo display method, it has the following advantages: (1) It can be applied to the Android system, so as to realize the native support for the touch screen and have a better human-computer interaction experience. (2) The system first draws the radar echo image that needs to be refreshed at a high speed in one texture, and then draws the azimuth circle, range mark circle, bow line and other content that do not need to be refreshed at a high speed in another texture. Some textures can be refreshed to have higher rendering efficiency. (3) At present, the graphics cards of common intelligent terminals can all support OpenGL technology, so they do not depend on specific hardware.

Description of drawings

Figure 1 shows the radar system structure.

Figure 2 is the main interface of the radar display and control software.

Figure 3 shows the improved data storage model of the secondary index.

Figure 4 is a frame diagram of echo image display.

Fig. 5 is a flowchart of a radar echo display method under the Android system.

Figure 6 shows the rendering effect of radar echoes based on this method.

specific implementation plan

Further describe the technical scheme of the present invention in detail below in conjunction with accompanying drawing:

Referring to Figure 1 of the manual, the hardware environment of this method is shown in the figure. The radar antenna sends the original signal to the signal transceiver module for noise suppression and clutter processing, and then sends the echo data, clock data, bow and azimuth data to the The display and control terminal displays. The software operation interface where the display and control terminal is located is shown in Figure 2. The display and control interface consists of three parts: radar image display area, ship information display area, and menu area. The radar image display area mainly includes radar echo images, warning areas, AIS targets and track points, etc. Figure 6 shows the rendering effect of radar echoes based on this method.

Step 1: Construct a mapping table T from polar coordinates to rectangular coordinates in memory. The storage structure is shown in Figure 3, where m is the number of Cartesian coordinate points (the number of pixels in a square area with a side length of 2048 pixels), the structure consists of two one-dimensional data tables, and the index table can be queried through r and θ s and l are obtained, and the rectangular coordinate set is found in the rectangular coordinate table through s and l, and this set is the final table lookup result. Where r and θ are the polar coordinate radius and angle of the point to be queried, respectively, and s and l are the starting position and length of the target set in the Cartesian coordinate table, respectively. Described step one comprises two sub-steps:

Step 1 (1), create a one-dimensional linked list array L[keyIdx] (0≤r≤MaxRng, 0≤θ≤MaxDeg, where MaxRng is the maximum display radius, MaxDeg is the maximum quantization angle, the height of the radar image display area is 2R, keyIdx represents the one-dimensional index value of the point in polar coordinates), where keyIdx is calculated according to the following formula:

Step 1 (2), calculate the one-dimensional index value valueIdx under the Cartesian coordinates of this point, and store it in the linked list L[keyIdx];

Step 1 (3), optimizing the storage structure of the table L. First initialize an empty index table I and an empty rectangular coordinate table T, and obtain the linked list array L to be optimized;

Step one (four), find corresponding link list S in L for each polar coordinate point on the screen, and store the size of S and the capacity of T in I;

Step 1 (5), put all the elements in S into T.

Step 2: Create two 2D texture buffers F and B of equal size. There are two texture buffers in the custom Renderer object, the size is set to 1024×1024×4Byte, one buffer is used to draw radar echo video, the other is used to draw secondary information such as AIS target and navigation route, and initialize the display Control system UI background color. Subsequent operations only need to be performed on the texture buffer to complete the image drawing, which is consistent with the effect of directly operating the video memory.

Step 3. Update the azimuth circle, range marker circle, and bow line in F in the form of points.

Step 4: Receive and analyze the echo data of the radar antenna, and store the frame data into the echo buffer.

Step 5. Update B with the data in the echo buffer. This step contains four substeps:

Step five (1), check whether the cumulative echo angle difference in the echo buffer is greater than or equal to a given split angle, if not, then end step five;

Step 5 (2): Obtain the last two frames of data D ₁ and D ₂ stored in the echo buffer, obtain the echo data E and the starting angle θ ₁ from D ₂ , and obtain the ending angle θ ₂ from D ₁ ;

Step 5 (3), for each point on the screen whose angle is greater than or equal to θ ₁ and less than θ ₂ , find its Cartesian coordinates in T, and update in B with data E;

Step five (four), remove D ₁ and D ₂ from the echo buffer.

Step 6: Build a rendering environment and use OpenGL texture mapping technology in Android to render radar echo images. Accompanying drawing 4 illustrates the construction of rendering environment and the application of texture mapping technology, this step includes nine sub-steps:

Step 6 (1), create GLSurfaceView and a custom View object inherited from GLSurfaceView.Renderer and a Renderer (renderer) object in Android, and call the setRenderMode function to set the rendering mode to GLSurfaceView.RENDERMODE_WHEN_DIRTY;

Step 6 (2), initialize the viewport through the function gl.glViewport(0,0,1080,1080);

Step 6 (3), initialize the frustum through the function gl.glFrustumf(left, right, bottom, top, zNear, zFar). Left is -540, right is 540, bottom is -540, top is 540, zNear is 3, zFar is 7;

Step six (four), set the projection mode through the function gl.glMatrixMode(GL10.GL_MODELVIEW), then clear the color buffer and load the identity matrix;

Step 6 (5), generate two texture numbers through the function gl.glGenTextures(2,ts,0), and associate them with F and B respectively, where ts is an array storing the texture object numbers;

Step 6 (6), enable the texture blending function through the function gl.glEnable(GL10.GL_BLEND), and set the texture blending mode through the function gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE_MINUS_SRC_ALPHA);

Step six (seven), bind the texture through the function gl.glBindTexture;

Step six (eight), update the texture with the data in B and F through the function gl.glTexSubImage2D;

Step six (nine), request the system to render the screen through the function requestRender.

Claims (3)

1. a radar echo display method under the Android system, is characterized in that, comprises the following steps: Step 1, constructing a mapping table T from polar coordinates to rectangular coordinates in memory; Step 2. Create two 2D texture buffers F and B of equal size; Step 3. Update the azimuth circle, range marker circle, and bow line in F in the form of points; Step 4: Receive and analyze the echo data of the radar antenna, and store the frame data in the echo buffer; Step five, update B with the data in the echo buffer, this step includes four sub-steps: Step five (1), check whether the cumulative echo angle difference in the echo buffer is greater than or equal to a given split angle, if not, then end step five; Step 5 (2): Obtain the last two frames of data D ₁ and D ₂ stored in the echo buffer, obtain the echo data E and the starting angle θ ₁ from D ₂ , and obtain the ending angle θ ₂ from D ₁ ; Step 5 (3), for each point on the screen whose angle is greater than or equal to θ ₁ and less than θ ₂ , find its Cartesian coordinates in T, and update in B with data E; Step five (four), remove _D1 and _D2 from the echo buffer; Step 6. Using OpenGL texture mapping technology in Android to render the radar echo image. 2. the radar echo display method under a kind of Android system according to claim 1, is characterized in that, described step 1 comprises the following steps: Step 1 (1), for each point (x ₁ , y ₁ ) in the screen, calculate its corresponding polar coordinates, and put the mapping relationship of this point from polar coordinates to rectangular coordinates into table L; Step 1 (2), traversing the table L, and storing the mapping relation of the angle and the radius as the key and the corresponding Cartesian coordinate as the value into the new data table T. 3. The radar echo display method under a kind of Android system according to claim 1 or 2, is characterized in that, described step 6 comprises the following steps: Step 6 (1), create a GLSurfaceView and a custom View object and a Renderer object inherited from GLSurfaceView.Renderer in Android, and set the rendering mode to dirty rendering; Step 6 (2), initialize the viewport through the function gl.glViewport(0,0,width,height). Where width is the screen width and height is the screen height; Step 6 (3), initialize the frustum through the function gl.glFrustumf(left, right, bottom, top, zNear, zFar), left is -0.5×width, right is 0.5×width, bottom is -0.5×height, top is 0.5×height, zNear is 3, zFar is 7; Step six (four), set the projection mode through the function gl.glMatrixMode(GL10.GL_MODELVIEW). Then clear the color buffer and load the identity matrix; Step 6 (5), create two textures through the function gl.glGenTextures(2,ts,0), and associate them with F and B respectively, where ts is an array storing the number of texture objects; Step 6 (6), enable the texture blending function through the function gl.glEnable(GL10.GL_BLEND), and set the texture blending mode through the function gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE_MINUS_SRC_ALPHA); Step six (seven), bind the texture through the function gl.glBindTexture; Step six (eight), update the texture with the data in B and F through the function gl.glTexSubImage2D; Step six (nine), request the system to render the screen through the function requestRender.