CN101645166A - Method for realizing direction selection of electronic chart - Google Patents

Abstract

The invention relates to a method for realizing the direction selection of an electronic chart, which comprises the following steps: establishing a mathematical model according to an established coordinate system; deducing a calculating method from geographic coordinates to screen coordinates; reading the information of each coordinate point of the chart in a database; then confirming a screen coordinate point of a point to be drawn according to a rotating angle by coordinate conversion; and finally, drawing the rotated chart. The invention can realize the random angle rotation of the electronic chart and lead the advancing directions of various moving objects in an electronic chart system to maintain consistence with the upper part displayed by the chart and has the function of leading adriver to more conveniently, easily and visually use the system, which is more important for an airplane in the air and a ship in the sea.

Description

Electronic chart is realized the method that direction is selected

Technical field

The present invention relates to electronic chart display and infor mation system, particularly a kind of electronic chart is realized the method that direction is selected.

Background technology

Electronic chart display and infor mation system (Electronic Chart Display and Information System, ECDIS) be along with seafaring and development of science and technology and a kind of integrated real-time navigation infosystem that produces, it can be superimposed upon nautical chart information, navigation information and radar target information on the screen and show, is bringing into play significant effect aspect guarantee navigation safety and the raising navigation work efficiency.It finishes multiple monitoring function about marine engineering facility and boats and ships shipping safety on the basis that shows electronic chart, have functions such as sea chart demonstration, accommodation tracking and demonstration, navigational hazard warning, navigational record, radar image stack and other auxiliary behaviour's ship decision-makings.Because it can improve the security of navigation forecast effectively, so be extensive use of by ships that transport both domestic and external and VTS bank station management system for monitoring.

In most at present electronic chart systems, the display direction of sea chart is all fixed, and is promptly the same with the paper map, up north and down south.

In the electronic chart system applies, a kind of scheme that realizes spinfunction is to realize the rotation of sea chart when charting by rotation paintbrush function, implements very convenient like this.But lose genuine situation by the sea chart image that rotation paintbrush function is drawn, Chinese character and figure all have the effect of the distortion torn, have the discontinuous situation of appearance point after for example literal is drawn through rotation, be not easy identification, can cause the location inaccurate like this, and the user is visually also very uncomfortable, so realizes on the electronic chart that undistorted image rotating has just become a difficult problem that needs to be resolved hurrily.

Summary of the invention

Purpose of the present invention is exactly the problem that exists at prior art, a solution is provided, in the hope of a difficult problem effective and more than high-quality the solution, realize on the electronic chart that can select any direction is the visual angle, reaches arbitrarily angled image rotating and distortionless effect.

The present invention realizes by such technical scheme: a kind of electronic chart is realized the method that direction is selected, according to the coordinate system of setting up, set up mathematical model, derive the computing method of geographic coordinate to screen coordinate, the information of each coordinate points of sea chart in the reading database, determine the screen coordinate point of the point that will draw then according to the anglec of rotation by coordinate conversion, draw out postrotational sea chart at last, described method comprises the steps:

(1) in the electronic chart system, sets up coordinate system; The lower left corner with sea chart is initial point, and the direction that increases with longitude is the positive dirction of x axle, and the direction that increases with latitude is the positive dirction of y axle, sets up plane right-angle coordinate;

(2) on the basis of existing coordinate system, set up the rotation of coordinate mathematical model:

In the X-Y coordinate system certain a bit (x, y) line and the formed angle of X-axis positive dirction with central point is α, central point get the coordinate of screen central point (CenterX, CenterY), then postrotational screen coordinate (x1, y1):

$\mathrm{angel}=\arctan \frac{x-\mathrm{CenterX}}{y-\mathrm{CenterY}}+\mathrm{\&alpha;}+\mathrm{\&pi;},x<\mathrm{CenterX}$

$\mathrm{angel}=\arctan \frac{x-\mathrm{CenterX}}{y-\mathrm{CenterY}}+\mathrm{\&alpha;},x<\mathrm{CenterY}$

Following formula is the rotation of coordinate mathematical model, and wherein angel is an intermediate variable;

(3), calculate geographic coordinate according to input sea chart rotation angle value and change to screen coordinate with sea chart rotation angle value input coordinate rotation mathematical model;

(4) judge the angle quadrature according to step 3 result;

(5) draw out postrotational sea chart according to the angle of require rotation.

Advantage of the present invention is, can realize the arbitrarily angled rotation of electronic chart, the preceding line direction of various moving objects in the electronic chart system and the top of sea chart demonstration are consistent, can allow the driver convenient, use this system easily, intuitively, and also do not have the electronic chart system applies to cross this scheme in the past.For aerial aircraft and big marine boats and ships, it is even more important that this function will seem.This function will be referred to the technical matterss such as conversion of foundation, sea chart display algorithm and the various geographic coordinates of coordinate system.

Description of drawings

Fig. 1 is that sea chart rotation is drawn process flow diagram and as Figure of abstract;

Fig. 2 is a rotation of coordinate model synoptic diagram.

Embodiment

In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated, be to be understood that, specific embodiment described herein is only in order to explaining the present invention, and is not used in qualification the present invention.

The first step: in the electronic chart system, set up coordinate system

The basis of ECDIS system is the digitizing of sea chart, promptly convert paper chart to digital chart exactly, but digital chart is not merely directly to be replicated in the content of paper chart on the screen, it must have unique data structure, makes the information on the sea chart set up one-to-one relationship with actual geography information.That is to say that all points necessarily belong to certain geographical entity (as: island, land, beacon etc.) on the ECDIS display, otherwise all geographical entities can be represented with point, line, surface on the screen etc.For describing this corresponding relation definitely, must set up the coordinate-system that is suitable for ECDIS.After having set up the coordinate system of electronic Chart Display and infosystem, can reduce the complicated process of plotting, improve the precision of navigator fix. after setting up, could further extrapolate coordinate system the conversion relation of screen coordinate and geographic coordinate.

The following describes the process of setting up of the coordinate system on the electronic curtain:

As shown in Figure 1 and Figure 2, be initial point with the lower left corner of sea chart, the direction that increases with longitude is the positive dirction of x axle, the direction that increases with latitude is the positive dirction of y axle, sets up plane right-angle coordinate, and is referred to as the x-y coordinate system, has so just determined screen coordinate.For the arbitrfary point on the sea chart, can both calculate the latitude and longitude value of this point, thereby can retrieve the data relevant, if the point in the marine site is then known the Hai Shen at this place with this point; If what restriction the restricted area has then known; If beacon then can obtain the particulars of beacon.Otherwise, can pass through GPS or other positioning equipment, measure the longitude and latitude on naval vessel, and automatically it is converted into screen coordinate, be plotted on the screen.

Second step: on the basis of existing coordinate system, set up mathematical model.

After having set up coordinate system, just can set up mathematical model and calculate the conversion of geographic coordinate to screen coordinate.Be the mathematical model of setting up below: be illustrated in figure 2 as the rotation of coordinate model;

Among the figure α be illustrated in the X-Y coordinate system certain a bit with the line and the formed angle of X-axis positive dirction of central point, central point is got the central point of the coordinate of screen.

The 3rd step calculated geographic coordinate according to the input angle value and changes to screen coordinate

Narrate below and how to calculate the conversion of geographic coordinate to screen coordinate:

Get a certain coordinate points q in the sea chart, the longitude and latitude of q be (λ, δ), the anglec of rotation that q is ordered is that (α is zero to α when the anglec of rotation is zero, be the situation when not rotating at this moment), the coordinate figure of screen center's point is respectively centerX and centerY, and how many screen coordinate x1 and y1 of asking q to order be.

At first the latitude and longitude coordinates value of ordering according to q calculate before the q point rotation screen coordinate for (x, y), then according to (x, y) and anglec of rotation α obtain the coordinate of the point of rotation.

Get variable a and b:

a＝x-CenterX； (1)

b＝y-CenterY； (2)

Get variable R:

$R=\sqrt{a^2+b^2};---\left(3\right)$

On behalf of R, following formula equal the square root of a and b.

Get variable angel:

angel＝arctan(b/a) (4)

Following formula represents that angel equals the arc tangent angle value of b than a, can draw the angle of angel for which quadrant by a:

If a is less than zero so:

angel＝angel+α+π； (5)

If a is greater than zero so:

angel＝angel+α； (6)

Can calculate the x1 of postrotational screen point and the coordinate figure of y1 according to the above condition of calculating at last

Drawn geographic coordinate behind the algorithm of screen coordinate, then can draw out postrotational sea chart according to the angle of require rotation.

When for example drawing certain geographical entity such as island, at first taking out the geographic coordinate (latitude and longitude value) of the every bit on island, is 122.09 with longitude, and latitude is an example for-31.45 point, the screen coordinate point when calculating rotation 45 is spent.

The screen coordinate value of calculating earlier before not having to rotate is that x equals 491.2, and y equals 60.9, then draws a and equals-18.7, b equals-264.04, can judge the angle that angel is a third quadrant, draws angel and equals 5.42, calculate postrotational screen coordinate value x at last and equal 683, y equals 125.

At last, when system need obtain geographic coordinate according to a certain coordinate points in the screen, then need the anti-derivation of screen coordinate to geographic coordinate.Behind the corresponding relation of setting up by coordinate system in the electronic chart system between screen coordinate and the terrestrial coordinate, only need cursor is pointed to any point on the electronic chart, system will extrapolate the latitude and longitude value of this point automatically and show on screen, and can find the particulars of this point.As: whether is the safety depth marine site, be tower etc.The conversion method of screen coordinate to geographic coordinate is described below:

Get a certain coordinate points p in the sea chart, the screen coordinate of p be (x2, y2), the anglec of rotation that p is ordered is α, the coordinate figure of screen center's point is respectively CenterX and CenterY, how many longitudes and latitudes of asking p to order is.

Get variable a and b:

a＝x2-CenterX； (9)

b＝y2-CenterY； (10)

If it is zero can directly calculate geographic coordinate values that all null words of a and b are represented the anglec of rotation, if non-vanishing words can be calculated by following formula:

Get variable R:

$R=\sqrt{a^2+b^2};---\left(11\right)$

It is the square root of a and b that following formula is represented R.

Get variable angel

angel＝atan(b/a)； (12)

Following formula represents that angel equals the arc tangent angle value of b than a, can draw the angle of angel for which quadrant by a,

If a is less than zero so:

angel＝angel-α+π； (13)

If a is greater than zero so:

angel＝angel-α； (14)

Obtain rotation preceding screen coordinate point (x3, value y3) then

X3＝R*cos(angel)+CenterX； (15)

Y3＝R*sin(angel)+CenterY； (16)

(x3 y3) draws the geographic coordinate values that rotates preceding point by the screen coordinate point before the rotation at last.

After the method that the present invention adopts realized spinfunction, the distortion of electronic chart was little, and it is more accurate to locate.And can be from the anti-geographic coordinate values of releasing of screen coordinate, for inquiry, the search of sea chart are provided convenience.Electronic chart is being brought into play increasing effect in modern sea chart system, the present invention brings convenience also can for the widespread use of sea chart.

According to the above description, can realize technical scheme of the present invention in conjunction with techniques well known.

Claims (1)

1, a kind of electronic chart is realized the method that direction is selected, according to the coordinate system of setting up, set up mathematical model, derive the computing method of geographic coordinate to screen coordinate, the information of each coordinate points of sea chart in the reading database, determine the screen coordinate point of the point that will draw then according to the anglec of rotation by coordinate conversion, draw out postrotational sea chart at last, described method comprises the steps:

(1) set up coordinate system in the electronic chart system: the lower left corner with sea chart is initial point, and the direction that increases with longitude is the positive dirction of x axle, and the direction that increases with latitude is the positive dirction of y axle, sets up plane right-angle coordinate;

(2) on the basis of existing coordinate system, set up the rotation of coordinate mathematical model:

In the X-Y coordinate system certain a bit (x, y) with the line and the formed angle α of X-axis positive dirction of central point, central point get the coordinate of screen central point (CenterX, CenterY), then postrotational screen coordinate (x1, y1) with formula:

$\mathrm{angel}=\arctan \frac{x-\mathrm{CenterX}}{y-\mathrm{CenterY}}+\mathrm{\&alpha;}+\mathrm{\&pi;}$ x＜CenterX

$\mathrm{angel}=\arctan \frac{x-\mathrm{CenterX}}{y-\mathrm{CenterY}}+\mathrm{\&alpha;}$ x＞CenterY

Be the rotation of coordinate mathematical model, wherein angel is an intermediate variable;

(3) with sea chart rotation angle value input coordinate rotation mathematical model: calculate geographic coordinate according to input sea chart rotation angle value and change to screen coordinate;

(4) judge the angle quadrature according to step 3 result;

(5) draw out postrotational sea chart according to the angle of require rotation.

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