CN104613967B - The chart management method of portable airborne navigation system - Google Patents

Abstract

A chart management method for a portable airborne navigation system. It includes obtaining the coordinate calibration of the aeronautical chart; completing the positioning of the aircraft; layering and segmenting the aeronautical chart to obtain the sub-map of the aeronautical chart; setting the focus information of the aircraft display position in the navigation system; determining the focus sub-map index of the sub-map where the aircraft is located; Realize the initial display of the background chart of the navigation system; translate and rotate the background chart of the navigation system; zoom in and out of the background chart of the system according to the zoom operation of the user. The navigation chart management method of the portable airborne navigation system provided by the present invention uses the standard navigation chart as the background of the airborne navigation system. Under the condition of limited memory space, the navigation chart is layered and divided in a quadtree manner, through The effective indexing and calling of aviation can realize the loading, translation, rotation, zooming and other operations of the navigation system on the chart, thus effectively solving the inherent efficiency problem of chart occupation.

Description

Aircraft Chart Management Method for Portable Airborne Navigation System

technical field

The invention belongs to the technical field of navigation, and in particular relates to a low-cost, high-reliability, portable navigation chart management method of a portable airborne navigation system.

Background technique

As an important system to ensure navigation safety, the airborne navigation system can provide real-time aircraft position, speed, attitude and other information for other airborne systems and pilots. Especially in performance based navigation (PBN), the performance of the onboard navigation system directly affects the operation of the aircraft, so it is very important to the safety of navigation. At present, the common airborne navigation systems mainly include: inertial navigation system, air data system, satellite navigation system, short-range land-based radio navigation system, etc. These airborne navigation systems are usually relatively expensive, and are often only equipped on larger and expensive public transport aircraft. For general aviation aircraft, due to its small size, low load, slow speed, low altitude, and low price, an airborne navigation system with a simple structure, low price, and able to meet the needs of safe operation is usually selected.

At present, the research on airborne navigation system is mainly based on the system developed by desktop computer or portable computer. The combination of information displays the navigation information on the chart, and the other is to use GPS to provide aircraft position information and indicate the position of the aircraft on the electronic chart. The main problem with these systems is the poor portability of the system.

With the emergence of a large number of tablet electronic products, civil aviation has begun to use tablet computers as electronic flight bags (Electronic Flight Bag, EFB). The electronic flight bag is a portable electronic device used by pilots to display various navigation data and perform calculations and inspections during various flight preparations. Although the electronic flight bag can replace the traditional paper chart to a certain extent, it cannot realize the real-time display of the aircraft position.

The emergence of tablet computers, especially those with built-in GPS function, has made it possible to develop portable airborne navigation systems. However, due to the limited internal space of the tablet computer, it is impossible to simply load the aeronautical chart, so it is necessary to study the loading and management of the aeronautical chart.

Contents of the invention

In order to solve operations such as indexing, loading, translation, rotation, and zooming of the chart background of the portable airborne navigation system, the object of the present invention is to provide a chart management method for the portable airborne navigation system.

In order to achieve the above object, the present invention provides a chart management method of a portable airborne navigation system comprising the following steps carried out in sequence:

1) According to the coordinates of several key points in the airborne navigation system used by the airborne navigation system, obtain the S1 stage of the mapping relationship between the latitude and longitude coordinates of the airborne chart and the pixel coordinates of the bitmap;

2) According to the mapping relationship between the latitude and longitude coordinates of the aeronautical chart obtained in step 1) and the pixel coordinates of the bitmap, the bitmap pixel coordinates of the aircraft on the aeronautical chart are calculated from the latitude and longitude coordinate information of the aircraft, so as to complete the positioning of the aircraft, thereby obtaining the position of the aircraft and its front and rear S2 stage of location information;

3) Using the quadtree method to stratify and divide the chart to obtain the S3 stage of the chart sub-graph;

4) Set the S4 stage of the focus information of the aircraft display position in the navigation system;

5) According to the aircraft position information obtained in step 2) and the sub-map of the sub-map after the segmentation in step 3), determine the S5 stage of the focus sub-map index of the sub-map where the aircraft is located;

6) According to the focus submap indexed in step 5) and the default information of the system focus, place the focus submap and related adjacent submaps on the display screen to realize the S6 stage of initializing and displaying the navigation chart background of the navigation system;

7) According to the position information before and after the aircraft obtained in step 2), the focus information of step 4) and the focus submap of step 5), the S7 stage of translating and rotating the background chart of the navigation system;

8) Using the focus information in step 4) and the focus sub-image in step 5), according to the user's zoom operation, the system background chart is zoomed in S8 stage.

In step 1), the method for demarcating the coordinates of the aeronautical chart to obtain the mapping relationship between the longitude and latitude coordinates of the aeronautical chart and the bitmap pixel coordinates according to the coordinates of several key points in the aeronautical chart used by the airborne navigation system is: adopt a fitting The algorithm establishes the transformation matrix between the longitude and latitude coordinates and the bitmap pixel coordinates of the aeronautical chart, and uses the latitude and longitude coordinates of no less than three known waypoints on the standard aeronautical chart to establish a system of equations, and uses the least squares algorithm to solve the unknown parameters in the transformation matrix , to obtain the mapping relationship between the latitude and longitude coordinates of the aeronautical chart and the pixel coordinates of the bitmap.

In step 3), the method for stratifying and segmenting the chart by adopting the quadtree method to obtain the sub-map of the chart is: defining the original chart with the highest resolution as the 0th layer, and distinguishing The rate is used as the normalized resolution, and the M-layer charts with different resolutions are obtained by extracting pixels, and then each layer of charts is divided into standard-sized sub-pictures with the size of the navigation system display screen as a parameter.

In step 4), the method for setting the focus information of the display position of the aircraft in the navigation system is: defining the screen position of the aircraft as the focus, and the information representing the focus includes the screen position information and heading information displayed by the aircraft, The focus information either adopts the system default setting information, or adjusts it through user operations.

In step 5), the method for determining the focus submap index of the submap where the aircraft is located is to use the aircraft position information obtained in step 2) and the submap of the aeronautical map after step 3) to determine the index of the focus submap of the submap obtained in step 2). For the aircraft position information, according to the default resolution of the system, the submap where the aircraft is located is determined in the submaps of different layers divided in step 3), that is, the focus submap.

In step 6), according to the default information of the focus submap indexed in step 5) and the system focus, the focus submap and related adjacent submaps are placed on the display screen to realize the initial display of the navigation chart background of the navigation system The method is: according to the default focus information of the system, place the focus submap indexed in step 5) at the corresponding position, and place the adjacent submaps of the same layer of the focus submap in the display background in order to form the initial chart background stitching.

In step 7), the method for translating and rotating the background chart of the navigation system is as follows: When the position of the aircraft changes, use the front and rear position information of the aircraft obtained in step 2) to calculate the flight distance and heading of the aircraft, and combine the focus information in step 4) to convert the translation and rotation of the background chart. The figure is translated and rotated accordingly.

In step 8), the method of using the focus information in step 4) and the focus submap in step 5) to zoom the system background chart according to the zoom operation of the user is: , Lower threshold value comparison, when the zoom rate is within the threshold range, the chart layer will not be changed, and the zoom display will be performed in this layer; if the zoom rate exceeds the threshold, then switch to a new layer, by loading a new map The submap of the layer is zoomed and displayed, and the zoom rate is updated with the switching of the layer.

The navigation chart management method of the portable airborne navigation system provided by the present invention uses the standard navigation chart as the background of the airborne navigation system. Under the condition of limited memory space, the navigation chart is layered and divided in a quadtree manner, through The effective indexing and calling of aviation can realize the loading, translation, rotation, zooming and other operations of the navigation system on the chart, thus effectively solving the inherent efficiency problem of chart occupation.

Description of drawings

Fig. 1 is the flowchart of the chart management method of the portable airborne navigation system provided by the present invention;

Figure 2 is an effect diagram of system chart coordinate calibration;

Figure 3 is a partially enlarged rendering of the system background chart;

Figure 4 is the rendering of the system chart after translation and rotation;

Fig. 5 is a schematic diagram of the dynamically updated aircraft position information.

detailed description

The chart management method of the portable airborne navigation system provided by the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a flowchart of the chart management method of the portable airborne navigation system provided by the present invention.

As shown in Figure 1, the chart management method of the portable airborne navigation system provided by the present invention comprises the following steps carried out in order:

1) According to the coordinates of several key points in the airborne navigation system used by the airborne navigation system, obtain the S1 stage of the mapping relationship between the latitude and longitude coordinates of the airborne chart and the pixel coordinates of the bitmap:

The real-time latitude and longitude information of the aircraft in the present invention comes from the built-in GPS module of the portable device, and the airborne navigation system takes the standard air chart as the background, so its primary task is to mark the aircraft on the correct position of the air chart. Since the standard aeronautical chart is provided in the form of a bitmap, the latitude and longitude coordinates of the aircraft provided by the GPS module need to be converted into the bitmap pixel coordinates of the aeronautical chart, so as to mark the aircraft at the correct position on the aeronautical chart. The process of converting aircraft latitude and longitude coordinates into bitmap pixel coordinates is called chart coordinate calibration.

In the standard chart, since the latitude and longitude coordinates of key waypoints such as navigation stations and airports are known, these key point coordinates can be used to calibrate the chart. Assuming that the latitude and longitude coordinates of N key waypoints can be obtained on the chart, (λ _n , θ _n ) is the latitude and longitude coordinates of the nth key waypoint, and the pixel coordinates of the waypoint that can be obtained on the chart are estimated as Using a fitting algorithm can get:

in, It is a 2×N dimensional data matrix formed by the pixel coordinate estimation of N key waypoints selected in the navigation chart, specifically:

G is a 3×N dimensional data matrix composed of latitude and longitude of corresponding waypoints,

A is a 2×3 dimensional calibration matrix,

E is a 2×N dimension calibration error matrix.

The chart coordinate calibration process is the process of estimating the calibration matrix A from formula (1), which can be solved by the least square method, namely:

The estimated value of the calibration matrix can be obtained by solving formula (5):

Clearly, when a single fit is used, the calibration matrix estimates The premise that can be calculated by formula (6) is that the number of selected reference points N≥3, and with the increase of the number of selected reference points N, the estimated value of the calibration matrix calculated by formula (6) The accuracy also increases accordingly.

2) According to the mapping relationship between the latitude and longitude coordinates of the aeronautical chart obtained in step 1) and the pixel coordinates of the bitmap, the bitmap pixel coordinates of the aircraft on the aeronautical chart are calculated from the latitude and longitude coordinate information of the aircraft, so as to complete the positioning of the aircraft, thereby obtaining the position of the aircraft and its front and rear S2 stage of location information:

Aircraft positioning refers to the process of obtaining the pixel coordinates on the original standard chart from the longitude and latitude coordinates of the aircraft. The current latitude and longitude coordinates (λ ₀ , θ ₀ ) of the aircraft are provided by the built-in GPS module of the portable device. Estimated values using the calibration matrix

The bitmap pixel coordinates (x ₀ , y ₀ ) corresponding to the aircraft in the original standard chart can be calculated.

The distance and heading of the aircraft in the corresponding time interval can also be calculated by using the position changes before and after the aircraft.

3) Use the quadtree method to stratify and divide the aeronautical chart to obtain the S3 stage of the sub-graph of the aeronautical chart:

In this step, a quadtree is used to stratify and divide the chart. The segmentation of the aeronautical chart is to divide the aeronautical chart into several sub-graphs evenly with the agreed size. The layering of the aeronautical chart is to reduce the resolution, so that the sub-maps of different layers show different scales of the airspace range, so as to realize the management of the system's aeronautical charts at different resolutions.

The original standard chart with the highest resolution is defined as layer 0, and its resolution is taken as the normalized resolution. The M-layer aeronautical chart is obtained by extracting pixel points, which are respectively marked as 0, 1,..., (M-1) layers. The number of pixels between two adjacent layers is twice the relationship in the x and y axis directions, that is, the resolution of the m-th layer aeronautical chart is 1/2 ^m , so that the layer with low resolution is compared with the layer with high resolution , subgraphs of the same size, the former will present the navigation information of a larger area, and the latter will provide more detailed navigation information.

Assuming that the width and height of the tablet device display screen are w and h pixels respectively, define the parameters:

d=f(w,h) (8)

That is, the parameter d is determined by a certain functional relationship between w and h.

Make the upper left corner of the chart for each level of chart as the origin, and use the parameter d as the side length of the square sub-graph to divide the charts of each level. The r-th row and c-th column of the m-th layer aeronautical chart are defined as (m, r, c). Obviously, the upper left corner pixel of the sub-image (m,r,c) is the pixel in the [(r-1)d-1]th row and [(c-1)d+1]th column of the m-th layer aeronautical map .

Since the resolution between two adjacent layers is twice the relationship, the spatial range presented by a certain submap in the mth layer is presented by 4 submaps in the m-1th layer. 1/4 of the figure is presented.

4) Set the S4 stage of the focus information of the aircraft display position in the navigation system:

This step defines the position of the aircraft displayed on the navigation system screen as the focal point. The information involved in the focus includes the horizontal and vertical coordinates (x _c , y _c ) of the screen position where the focus is located, and the clockwise angle θ _c of the aircraft heading relative to the vertical upward direction of the screen, which can be comprehensively expressed as (x _c , y _c , θ _c ).

Focus information is the basis for loading, panning, rotating and zooming operations on the chart. The focus information can be preset by the system or modified by the user, so that the navigation system can observe different areas of interest.

5) According to the aircraft position information obtained in step 2) and the sub-graph sub-graph after the segmentation in step 3), determine the S5 stage of the focus sub-graph index of the sub-graph where the aircraft is located:

In this step, the submap in which the aircraft is located is defined as the focus submap. It can be known from step (4) that the focus subgraph is also the subgraph where the focus is. According to the segmentation sub-image parameter d in step (3), the sub-image number of the 0th layer aeronautical chart where the aircraft is located can be determined:

in Indicates a round-up operation. If the pixel in the upper left corner of the sub-image is defined as [1 1] ^T , that is, the element in row 1, column 1, the pixel coordinates of the aircraft in the sub-image are:

Because when the navigation system is started, the system background is not necessarily based on the 0th layer of the chart, but can be any layer in the 0~(M-1) layer. According to the system resolution s, available:

Determine the layer m where the focus chart is located.

According to the relationship between the upper and lower layers of the aeronautical chart, the sub-map of the aircraft on the 0th layer and the coordinate information of the sub-map determined by formulas (9) and (10) can be used to further determine the number of the sub-map of the aircraft on the m-th layer:

This subgraph is the focus subgraph. It is also possible to further determine the pixel coordinates of the aircraft in the focus submap:

6) According to the focus submap indexed in step 5) and the default information of the system focus, place the focus submap and related adjacent submaps on the display screen to realize the S6 stage of initializing and displaying the navigation chart background of the navigation system:

According to the focus sub-image (m,r _m ,c _m ) indexed in step (5), the pixel coordinates (x′ _m ,y′ _m ) of the aircraft in the focus sub-image and the system focus parameters (x _c ,y _c ,θ _c ) It can be determined that the coordinates of the pixel in the upper left corner of the focus sub-image on the screen are (x _c -x' _m +1, y _c -y' _m +1).

According to the principle of stratification and segmentation of the chart in step (3), the 8 submaps of the same layer related to the focus submap can be determined, which are (m, r _m ±1, c _m ±1), (m, r _m ,c _m ±1) and (m,r _m ±1,c _m ). These submaps and focus submaps are spliced together in order to form the initial chart background of the system.

7) According to the position information before and after the aircraft obtained in step (2), the focus information of step (4) and the focus submap of step (5), the S7 stage of translating and rotating the background chart of the navigation system:

When the user performs a translation operation on the display interface of the navigation system, the position of the aircraft is separated from the focus position, and the pixel coordinates at the focus need to be recalculated.

The change of the front and rear positions of the aircraft can be expressed by the change of the pixel coordinates of the aircraft on the 0th layer of the chart. Assume that the current pixel coordinate of the aircraft on the 0th layer of the chart is p _n = (x _n , y _n ), and the new pixel coordinate is p _n+1 = (x _n+1 , y _n+1 ). Due to the change of the position of the aircraft, it is necessary to translate and rotate the chart to bring the new position coordinates of the aircraft into focus. According to the focus parameters and the relationship between different layers of charts, the translation amount of the m-th layer chart as the display background is:

Among them, α is the system scaling rate, the default value is 1, and the user can modify it.

After the chart is translated, the rotation angle centered on the focal point can be provided by the direction finding equipment of the system, and can also be obtained from the front-back position relationship:

Δθ＝arg[p _n p _n+1 ]-arg[p _n-1 p _n ]+θ _c (15)

Among them, arg[p _n p _n+1 ] represents the argument of the vector from point p _n to point p _n+1 .

8) Using the focus information in step 4) and the focus submap in step 5), the S8 stage of zooming the system background chart according to the zoom operation of the user:

The invention allows users to zoom in and out of the chart to obtain better navigation display effect.

The zooming of the chart can not only be carried out in the chart of this layer, but also can occur when switching between adjacent layers. Once switching between different layers occurs, it is necessary to keep the focus information and direction information of the new layer's chart the same as the original layer.

When the system zoom rate α is greater than the zoom threshold α _in , the system background layer is switched from the mth layer to the m-1th layer, and the zoom rate is updated to α′=α/2, and the focus is re-indexed according to step (5) sub-map, and complete the background refresh process after the layer switching of the aeronautical chart by step (6).

When the system zoom rate α is less than the zoom-out threshold α _out , the system background layer is switched from the mth layer to the m+1th layer, and the zoom rate is updated to α′=2α, and the focus submap is re-indexed according to step (5) , and complete the background refresh process after the layer switching of the aeronautical chart by step (6).

When the system zoom rate α is within (α _out , α _in ), there is no inter-layer switching, and the submap of the corresponding layer is enlarged and displayed by α times.

The system amplification threshold α _in and reduction threshold α _out should satisfy:

In order to prevent switching jitter between adjacent layers, the thresholds α _in and α _out need to satisfy:

which is:

α _in >2α _out (18)

Experimental results

The effectiveness of the chart management method of the portable airborne navigation system provided by the present invention can be verified by the following experiments.

The Android development tool ADT of the Eclipse development platform is used to build a system simulation platform, and the Tianjin area of the air chart ZBAA is used as the experimental airspace, and the system function is verified by sending position simulation data to the system positioning module.

Use the navigation points PEK, CG, P75, NIKIT, and TONIL in the chart ZBAA to calibrate the chart, and then load the chart into the system according to the calibration results. Use the simulation platform to send the coordinates of the navigation point VYK to the system. It can be seen from Figure 2 that the system focus is correctly located at the position of the navigation point VYK. Figure 2 is partially enlarged, as shown in Figure 3. It can be seen that the system focus is accurately positioned at the navigation point VYK. Therefore, the navigation chart labeling method adopted by the present invention is effective.

Rotate and translate the scene shown in Figure 3, and the background of the chart changes as shown in Figure 4. Comparing Figure 4 and Figure 3, it can be seen that after the rotation and translation of the system display, what changes is the parameter of the focus, but the position between the aircraft and the chart does not change.

The aircraft position data is periodically sent to the system through the simulation platform, and the flight status of the aircraft is simulated by changing the aircraft position data. It can be seen from Fig. 5 that the change of the aircraft position parameter causes the relative position between the aircraft and the chart to change. Compared with Figure 2, the focus position of the system has not changed.

Claims (8)

1. A chart management method of a portable airborne navigation system is characterized by comprising the following steps: which comprises the following steps carried out in sequence:

1) s1 stage of obtaining the mapping relation between longitude and latitude coordinates of the navigation chart and the coordinates of the position image pixels according to the coordinates of a plurality of key points in the navigation chart used by the airborne navigation system;

2) according to the mapping relation between the longitude and latitude coordinates of the chart obtained in the step 1) and the position image pixel coordinates, calculating the position image pixel coordinates of the aircraft on the chart according to the longitude and latitude coordinate information of the aircraft, thereby completing the positioning of the aircraft and obtaining the position and the front and rear position information of the aircraft;

3) an S3 stage of obtaining a chart subgraph by layering and dividing the chart in a quadtree way;

4) stage S4 of setting the focus information of the display position of the aircraft in the navigation system;

5) determining a S5 stage of a focus subgraph index of the subgraph where the aircraft is located according to the aircraft position information obtained in the step 2) and the segmented subgraph in the step 3);

6) according to the focal point subgraph indexed in the step 5) and the default information of the system focal point, placing the focal point subgraph and the related adjacent subgraph on a display screen to realize the S6 stage of initializing and displaying the navigation chart background of the navigation system;

7) according to the position information of the front and the back of the aircraft obtained in the step 2), the focal point information in the step 4) and the focal point subgraph in the step 5), translating and rotating the background navigation chart of the navigation system at S7;

8) and S8, zooming the navigation chart of the system background navigation chart according to the zooming operation of the user by using the focus information of the step 4) and the focus subgraph of the step 5).

2. The method of claim 1, wherein the method further comprises: in step 1), the method for obtaining the mapping relationship between the longitude and latitude coordinates of the chart and the coordinates of the bitmap pixels according to the coordinates of a plurality of key points in the chart used by the airborne navigation system comprises the following steps: the method comprises the steps of establishing a conversion matrix between longitude and latitude coordinates and a navigation map position pixel coordinate by adopting a one-time fitting algorithm, establishing an equation set by utilizing the longitude and latitude coordinates of at least 3 known route points on a standard navigation map, and solving unknown parameters in the conversion matrix by adopting a least square algorithm to obtain a mapping relation between the longitude and latitude coordinates and the position image pixel coordinate of the navigation map.

3. The method of claim 1, wherein the method further comprises: in step 3), the method for obtaining the chart subgraph by layering and dividing the chart in the quadtree manner is as follows: defining the original chart with the highest resolution as a 0 th layer, taking the resolution as the normalized resolution, processing by extracting pixel points to obtain M layers of charts with different resolutions, and then dividing each layer of charts into subgraphs with standard sizes by taking the size of a display screen of a navigation system as a parameter.

4. The method of claim 1, wherein the method further comprises: in step 4), the method for setting the focal point information of the display position of the aircraft in the navigation system is as follows: the screen position of the aircraft is defined as a focus, the information representing the focus comprises screen position information and heading information displayed by the aircraft, and the focus information is adjusted by adopting system default setting information or user operation.

5. The method of claim 1, wherein the method further comprises: in step 5), the method for determining the focal sub-image index of the sub-image where the aircraft is located according to the aircraft position information obtained in step 2) and the segmented navigation sub-image in step 3) is as follows: determining a subgraph, namely a focus subgraph, where the aircraft is located in the subgraphs of the different layers segmented in the step 3) according to the default resolution of the system by using the aircraft position information obtained in the step 2).

6. The method of claim 1, wherein the method further comprises: in step 6), the method for placing the focus sub-image and the related adjacent sub-image on the display screen according to the focus sub-image indexed in step 5) and the default information of the system focus to realize the navigation chart background initialization display of the navigation system comprises the following steps: and (3) placing the focal subgraphs indexed in the step 5) at corresponding positions according to default focal information of the system, and sequentially placing adjacent subgraphs of the same layer of the focal subgraphs in a display background to form initial splicing of the navigation chart background.

7. The method of claim 1, wherein the method further comprises: in step 7), the method for translating and rotating the navigation system background chart according to the position information of the front and the back of the aircraft obtained in step 2), the focal point information in step 4) and the focal point subgraph in step 5) comprises the following steps: when the position of the aircraft changes, the flying distance and the flying course of the aircraft are calculated by utilizing the front and rear position information of the aircraft obtained in the step 2), and the translation amount and the rotation amount of the background chart are converted by combining the focus information in the step 4), so that the corresponding translation and rotation are carried out on the background chart.

8. The method of claim 1, wherein the method further comprises: in step 8), the method for zooming the navigation map of the system background navigation map according to the zooming operation of the user by using the focus information of step 4) and the focus sub-map of step 5) comprises: comparing the zoom ratio of the system with an upper threshold value and a lower threshold value, and when the zoom ratio is in the threshold range, zooming and displaying in the map layer without changing the map layer; and if the zoom rate exceeds the threshold, switching to a new layer, completing zoom display by loading the subgraph of the new layer, and updating the zoom rate along with the switching of the layer.