Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
2001-05-11
2003-11-25
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
Reexamination Certificate
active
06654014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a navigation system for detecting the position of a moving body to inform a user of the current position of the moving body, and a map display apparatus using the navigation system.
2. Description of Related Art
Various types of navigation systems have been recently known, and these navigation systems are used while mounted on moving bodies such as vehicles, ships, etc. When such a navigation system is mounted on a moving body, it performs arithmetic and logic processing on information provided from various sensors to detect the current position of the moving body and display the current position on a screen of the navigation system.
This type of navigation system includes a position detector for detecting the absolute position of the moving body, a storage device for storing map data which include two-dimensional vector data obtained by projecting roads and points on the ground, such as structures, etc., onto a mesh-segmented plane using a universal transverse Mercator projection method, and character data associated with the vector data, an input device for receiving external instructions (commands), and a display device for reading out desired vector data from the mesh-segmented map stored in the storage device in accordance with an instruction input from the input device, to perform data conversion processing on the data, and then displaying the map on the display.
The data conversion processing includes shift conversion processing for changing the display position on a map, scale conversion (enlarging/reducing) processing for displaying a map on any scale, and rotational coordinate-transformation processing for changing a display direction on the map. With these processings, a plan view map is obtained by drawing the ground through an orthogonal projection in a vertical direction.
As described above, when a map is displayed on the screen, the conventional navigation system as described above adopts a plan-map display mode in which the ground is drawn in the vertical orthogonal projection style. Therefore, in order to simultaneously display two spots which are far away from each other, a reduction-scale of the map must be necessarily increased, and thus detailed information cannot be displayed on the screen.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a bird's-eye view forming method for displaying a map of a plane (ground) on the basis of a bird's-eye view corresponding to a projected plan of the plane (ground) which is obtained by projecting the plane (ground) on any plane between the plane (ground) and a view point when the plane (ground) is viewed from the view point located at any height from the plane (ground), a map display apparatus using the bird's-eye view forming method, and a navigation system using the map display apparatus.
In order to attain the above object, a bird's-eye view forming method for forming, from map data, drawing (display) data for a map which is to be represented by a bird's-eye view, is characterized in that coordinate data contained in the map data are perspectively converted to drawing (display) data based on a bird's-eye view on a desired projection plane with a view point being set to a desired position (i.e., the coordinate data of the map data on a vertical orthogonal projection plane are perspectively converted to drawing (display) data on a desired projection plane based on a bird's-eye view).
The bird's-eye view forming method preferably includes a step of receiving an input of the position of the view point, and a step of determining the projection plane so that the drawing (display) positions of two predetermined spots (for example, a current position and a destination) which are obtained through a perspectively projecting transformation on the basis of the coordinates of the two spots in the map data and the position of the view point, are set to predetermined positions. (Here, the perspectively projecting conversion is defined as such a data conversion that data on a plan view are converted to data on a bird's-eye view through a perspective projection operation. Therefore, by using the perspectively projecting conversion, a plan-view map is converted to a bird's-eye view map. In the following description, the perspectively projecting conversion is merely referred to as “perspective projection”).
Alternatively, the bird's-eye view forming method may include a step of receiving an input of a scale, and a step of determining the position of the view point and the projection plane so that the drawing (display) positions of the two predetermined spots (for example, a current position and a destination) which are obtained by performing the perspective projection on the basis of the coordinates of the two spots in the map data and the input scale, are set to predetermined positions, and a scale of a drawn (displayed) map is equal to the input scale.
Further, the bird's-eye view forming method may include a step of receiving an input of a projection angle which is defined as an angle at which a plane defined for the map data and the projection plane intersect each other, and a step of determining the projection plane on the basis of the input projection angle and the set view point position.
Still further, according to the present invention, there are provided a map display apparatus for displaying a bird's-eye view by using the bird's-eye view forming method as described above, and a navigation system for displaying a map by using the map display apparatus.
According to the bird's-eye view display apparatus and the navigation system, map drawing means includes coordinate transforming means, and the coordinate transforming means performs the perspective projection (conversion) on the map data to convert a plan-view map to a bird's-eye view map, and to display the converted map on a screen. Therefore, according to the present invention, a user can obtain a bird's-eye view display which is easy to see and in which the user can easily recognize the positional relationship of spots displayed on the map. According to the bird's-eye view forming method of the present invention, the view point can be freely set, so that it can meet user's need.
According to the present invention, a navigation system which is excellent in operational performance and convenient for a user can be obtained if it is designed to overcome the following first to seventh problems.
Firstly, in the case where the processing speed of scroll processing in a bird's-eye view display mode is lower than that in a plan display mode, the operational performance may be degraded when the scroll processing is frequently used to search for a desired spot on the bird's-eye view display (first problem).
Therefore, it is preferable in the present invention that the plan view (plan map) display mode and the bird's-eye view display mode are freely switchable. With this switching operation, both the plan view display and the bird's-eye view display can be made in accordance with a user's requirement, and thus the convenience is enhanced.
In the above case, a second problem occurs, namely, that it is difficult for the user to grasp the positional relationship between two different type of view when display is switched between the plan view display and the bird's-eye view display. This is because the position of the same spot to be displayed on the screen varies significantly due to variation of the view point with respect to the map, when the display switching operation is performed, and further, spots which have not been displayed or have been displayed until the display switching time are respectively displayed or are not displayed at the display switching time.
Therefore, if the present invention is designed so that the display is freely switchable the plan view display and the bird's-eye view display, it is further preferable that an intersect
Endo Yoshinori
Fujiwara Toshio
Hirano Motoki
Kishi Norimasa
Satake Hiroyuki
Cao Huedung X.
Pennie & Edmonds LLP
Vo Cliff N.
LandOfFree
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