JPH052081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a nautical chart display device that displays a nautical chart in a track display device or the like that displays a ship's track on a CRT display.

(b) Conventional technology and its disadvantages Generally, in track display devices, etc., a certain range of existing nautical charts is sampled in advance at a certain number of points, which is stored as chart data, and the data of the points necessary for display are extracted. and display the nautical chart.

Conventional nautical chart display devices, such as track display devices, sample the entire Osaka Bay, including Awaji Island, at 1000 points, and cover the entire nautical chart with the same number of points whether the scale is expanded to its maximum or reduced to its maximum. Therefore, although it is sufficient for practical use when viewed as a whole of Osaka Bay, when zoomed in and viewed in part, only a small number of points are sampled and displayed on the entire screen, so the quality of the nautical chart is compared to the former. It had become far inferior.

For example, if Osaka Bay, including Awaji Island, is displayed at a scale of 1/530,000, it can be displayed with sufficient quality as a nautical chart, as shown in Figure 7. Therefore, there is no problem in determining the ship's position relative to Osaka Bay. If the map is then enlarged to a scale of approximately 1/130,000, it will be displayed as a nautical chart sufficient for ships navigating the Kitan Strait, as shown in Figure 8, but the display will be somewhat rough.
When further enlarged to a scale of approximately 1/33000, a very rough nautical chart display appears as shown in Figure 9.

As described above, although conventional nautical chart display devices are the same, nautical chart displays of different quality are performed depending on the scale ratio used. In order to solve this problem, the number of sampling points that make up the nautical chart can be increased, but this requires a long processing time when converting latitude and longitude information into screen display coordinates.

Therefore, for example, a method may be considered in which the position data is thinned out at a rate commensurate with a plurality of basic scale factors and only the thinned out data is displayed.

However, when displaying a nautical chart consisting of a plurality of points using such a method, an appropriate nautical chart may not be displayed simply by thinning out the points according to the scale factor. That is, if the latitude and longitude data of multiple points that make up a nautical chart are simply extracted every predetermined number of points with a certain point as a reference, for example, if a cape or the like is thinned out, a nautical chart without the cape will be displayed. In this case, areas that are originally land will be displayed as sea areas, creating an extremely dangerous situation for ships navigating near the cape. Therefore, an important issue is which data should be used for display among the latitude and longitude data of multiple points that make up the nautical chart.

(c) Purpose of the Invention The purpose of the present invention is to display a nautical chart with the same quality even if the scale of the nautical chart to be displayed is changed, and to shorten the processing time required to obtain the desired nautical chart.
Moreover, it is an object of the present invention to provide a nautical chart display device that can maintain the amount of information as a nautical chart and display it while preventing important points from being thinned out among a plurality of points constituting the nautical chart.

(d) Structure and effect of the invention The nautical chart display device according to claim 1 of the present invention has a priority display system that indicates the priority order in which latitude and longitude data of multiple points constituting a nautical chart should be displayed according to the scale factor. nautical chart storage means for storing the data along with ranking data; display point extraction means for extracting prioritized latitude and longitude data according to a designated scale rate from the chart storage means as display points; and latitude and longitude data for the display points. and coordinate conversion means for converting the image into screen display coordinate data.

Further, the nautical chart display device according to claim 2 includes a nautical chart storage means for storing latitude and longitude data constituting a nautical chart in advance in priority order, and latitudes up to the priority order according to a specified scale factor. - A display point extracting means for extracting longitude data as a display point from the chart storage means, and a coordinate conversion stage for converting the latitude and longitude data of the display point into coordinate data for screen display.

In the nautical chart display device according to claim 1 or 2 of the present invention, for example, when reducing the scale of the nautical chart to be displayed, more latitude and longitude data are thinned out from the nautical chart storage means. However, latitude and longitude data with higher priority are preferentially extracted as display points. On the other hand, when increasing the scale to be displayed, the number of thinnings is reduced and even data with low priority is extracted. Therefore, even if the scale rate changes, the nautical chart is always displayed with the data of the sampling number suitable for display, and data up to the priority level according to the scale rate is displayed, so for example, points with high priority such as capes are displayed. is displayed without being thinned out even when the scale factor is small (the denominator is large). Therefore, if the present invention is applied to a navigation aid device or the like, a highly safe nautical chart can be displayed.

(e) Embodiment <System configuration> FIG. 1 is a block diagram of a track display device that is an embodiment of the present invention.

In Fig. 1, 1 is a keyboard including screen enlargement keys and reduction keys, 2 is a navigation device such as a Loran receiver or a Detsuka receiver, 3 is an external memory such as a floppy disk device, and 4 is a device from a microprocessor, etc. 5 is a ROM that stores control programs or other data for this CPU,
6 is RAM used as registers, flags or other working area, 7 is color
CRT, 8 is a display memory that stores image data of three colors of R, G, and B; 9 is a converter that converts the output of this display memory 8 from parallel to serial; 10
is a graphic display controller that controls writing and reading from the display memory 8. The CPU 4 once loads the chart memory from the external memory 3 into the RAM 6, and reads out and uses the data to be displayed from therein. Also, CPU
4 reads position data from the navigation device 2 at regular intervals and stores it in the RAM 6. This accumulated position data is written in the display memory 8 as track information in accordance with the scale of the screen, thereby displaying the track.

When displaying a nautical chart based on nautical chart data, as the scale of the screen increases (the denominator becomes smaller), only a portion of the entire nautical chart data is actually displayed. In such a case, if it is determined one by one whether each point of the nautical chart data fits on the screen, the overall processing time becomes longer. Therefore,
Nautical chart data is divided into a plurality of sections in advance, stored for each section, and displayed in a short time by converting the coordinates of only the sections necessary for display.

<Operation of the Invention> Figure 2 shows a nautical chart of the entire Osaka Bay and its divisions. In FIG. 2, R is the range displayed at maximum enlargement, and a section approximately four times that range is stored as one group of chart data. For example, a nautical chart having a curve L (thick solid line) can be obtained from the data of the group in section 0.

Now, if you want to display the nautical chart in the area indicated by the thin broken line on the entire screen (for example, if your own ship is in the center of this square and you want to display it in the center of the screen), the relationship between the center position of the screen and the scale factor The nautical chart can be displayed based on the data in sections 1-9. Therefore, the latitude and longitude data for the data in sections 1 to 9 are converted into display coordinates (X/Y coordinates). At this time, the data corresponding to the thick solid line (excluding L) is subjected to coordinate transformation. Since the area outside the thin broken line is not displayed, converting the coordinates of that area will be a waste of processing time, but compared to the conventional processing method where the entire chart data is processed,
The time required for coordinate transformation is significantly reduced.

Next, when the screen center position moves and the display screen moves to the range indicated by the thick broken line, the chart data is limited to sections 2, 3, 5, and 6. In this way, each time the screen is rewritten, it is only necessary to search for the data of the necessary group and draw using only the data of that group.

FIG. 3 is a flowchart showing the above-mentioned processing procedure. The sections required for display are determined based on the latitude and longitude data at the center of the screen and scale data. The data of the group corresponding to the section thus obtained is read out, coordinates are transformed as described above, and drawing is performed. This process is performed sequentially for all necessary data.

<Explanation of drawing process> Figure 4 shows the drawing process based on one group of data.
FIG. 6 is a diagram illustrating how the data is adopted depending on the scale rate. Figure 4 is a diagram plotting each point of the nautical chart data regarding Tomogashima and Okinoshima. When the scale rate is H1/33000, all points (26
point) is extracted as a display point, but if the scale rate is 1/130000, 14 of the black circles (including double circles)
Extract the point as a display point and further scale it to 1/5300
In the case of 00, the four double-circled points are extracted as display points. The nautical chart indicated by the arrow in Figure 4 relatively represents the size of the nautical chart at a scale of 1/530,000 when the dashed line is 1/33,000. In this way, instead of simply extracting charts at equal intervals, by extracting data from points with high priority, it is possible to display charts with high display quality and a large amount of information with a small number of points. can.

FIG. 5 shows the stored contents of such chart data. In this way, as data for each point, data representing priority is stored along with latitude and longitude data. For example, latitude data is stored at address 0.
It stores LAT0, longitude data LON0, and priority data P0.

FIG. 6 is a flowchart for drawing a nautical chart based on the data shown in FIG. In FIG. 6, n20, n21, and n22 are scale rates N1, N2, and N whose scale rates to be displayed are predetermined.
This is the step of determining which of the ranges 3 is within. For example, if the scale factor is within the range of more than N1 and less than N2, a constant a2 is set for P in step n24. Here, P represents the priority order when extracting display points. At step n26, the data storage address MA is set to the initial value 0, and at step n27, the data storage address MA is set to the initial value 0.
Read LAT (MA), LON (MA), and P (MA) respectively. Thereafter, in step n28, control is performed to determine whether or not the read priority data P(MA) is less than or equal to the value set in step n24 described above. If it is less than or equal to (if the priority is high) n2
Latitude and longitude data LAT (MA), LON at 9
Convert (MA) to screen display coordinates, n30
Plot that point. After that, in n31, it is determined whether or not all stored data has been read, and if it is not finished, n3
The address MA is incremented at 2 and the process returns to 27. The data stored in this way is read out sequentially, and it is determined whether the point should be displayed, that is, whether it has a high priority or not. If the priority is high, the point is plotted as a display point. Note that step n30 not only plots points, but also performs processing for displaying a continuous line between the previously plotted points.

<Other Embodiments> In the embodiment described above, the latitude and longitude data of a plurality of points constituting a nautical chart are stored together with priority data indicating the priority to be displayed according to the scale ratio, and Priority latitude and
Although the longitude data is selectively extracted as display points, the latitude and longitude data can be extracted in priority order according to the specified scale factor using the method described below.

First, as for nautical chart data, latitude and longitude data of a plurality of points constituting a nautical chart are stored in advance in order of priority. When extracting display points from this nautical chart storage means, they are read out in order from the highest priority, and the latitude and longitude data up to the priority according to the specified scale factor are read out. Note that in order to connect the extracted points with a continuous line, order data for connecting the points is stored together with latitude and longitude data.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a track display device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between chart data and the display range of the screen, and FIG. 3 is a diagram showing the overall chart display of the track display device. Flowchart: FIG. 4 is a diagram showing an example of displaying a nautical chart, FIG. 5 is a diagram showing an example of storing nautical chart data, and FIG. 6 is a flowchart showing the procedure of a drawing process. Also, Figures 7 and 8
9 and 9 are diagrams showing display examples at different scales in a conventional nautical chart display device.

Claims (1)

[Scope of Claims] 1. A nautical chart storage means for storing latitude and longitude data of a plurality of points constituting a nautical chart together with priority data indicating the priority order to be displayed according to the scale ratio; A nautical chart display comprising: display point extracting means for extracting latitude and longitude data of priority order from the chart storage means as display points; and coordinate conversion means for converting the latitude and longitude data of the display points into coordinate data for screen display. Device. 2. A nautical chart storage means that stores latitude and longitude data constituting a nautical chart in advance in priority order, and a display point that extracts latitude and longitude data up to the priority order according to a specified scale rate from the nautical chart storage means as display points. A nautical chart display device comprising: an extraction means; and a coordinate conversion means for converting the latitude and longitude data of the display point into coordinate data for screen display.