DE102010025649A1 - Method for generating digital three-dimensional model for topographic terrain from digital map data for use by e.g. mobile telephone, for mountain route, involves determining height scale for generating model for selected topographic region - Google Patents

Abstract

The method involves selecting a defined topographic region by a subset of digital map data, where the subset is defined by a cluster in a map database. A height scale is determined for the selected region based on a fluctuation level by using a data base, where the fluctuation level indicates height fluctuation for the selected region in a z-direction. A digital model is generated for a part of the selected region based on the determined height scale and a predetermined longitudinal dimension scale. The fluctuation level is computed in real time for determining the height scale. Independent claims are also included for the following: (1) a computer program product with program code portions for performing a method for generating a digital three-dimensional (3D) model for a topographic terrain from digital map data (2) a device for producing a digital 3D model for a topographic terrain from digital map data.

Description

Field of the invention

The present invention relates to a technique for determining a height scale for a topographical terrain from digital map data, in particular for use by a navigation device.

State of the art

While the early navigation devices were only able to render digital map data in two dimensions, modern navigation devices often have the ability to create and display a three-dimensional model of topographical terrain from the digital map data. The three-dimensional model gives a user of the navigation device a more realistic impression of the terrain of interest.

However, it has turned out in practice that a three-dimensional rendering of the terrain does not sufficiently convey many topographical facts. Thus, in flat areas, the few surveys are often not sufficiently recognizable when the three-dimensional model is displayed on a display device of the navigation device. In heavily mountainous areas, in turn, the representation is often confusing because, for example, parts of a route may be covered by mountains.

In any case, it has been recognized that the deficiencies of conventional rendering techniques are in part due to the fact that the height scale and length scale match to produce the three-dimensional model.

Short outline

The present invention seeks to solve at least one of the problems described above as well as solutions to further problems.

According to the invention, a method is provided for generating a digital three-dimensional model for a topographical terrain from digital map data, in particular for a navigation device, wherein a length scale in the x / y direction and a height scale in the z direction are used for the model and wherein the method is the following Steps include: selecting a topographic region defined by a subset of the digital map data; Determining a height scale for the selected topographic region based on a measure of variance indicative of height variation in the z-direction for the selected topographic region; and generating a digital model for at least a portion of the selected topographic region based on the determined height scale and a predetermined length scale.

For example, the digital map data may include length and height information for entire countries or continents. Since such map data has been used for a long time in conventional navigation apparatuses, its structure and format will not be described here.

According to one embodiment of the method according to the invention, the height scale is determined using a database which in each case assigns a height scale to a plurality of predefined topographical regions, and wherein each height scale is based on a fluctuation factor calculated in advance for the assigned region. This approach can, for. B. solving the problem of inadequate real-time computing capacity, since region-specific fluctuation measures calculated offline and, for example, as additional parameters in the digital map data, which can also be stored in the database, can be integrated.

According to another development, the fluctuation amount (for example, by a navigation device) is calculated at least partially in real time. In addition, the fluctuation amount can be partially calculated in advance. That is, the level of fluctuation can be calculated either completely in advance, completely in real time, or partly in advance and partly in real time. In the case of a partial real-time calculation, the pre-share may indicate variations per area and / or screening, and the real-time part may allow refinement of the pre-calculated fluctuation measures for the topographical region (to be displayed). Also, in the case of partial real-time computation, the prebranch portion may indicate the number of polygons per region and / or rasterization, and the real-time component may allow for refinement of the pre-computed topographical region variability measures.

Based on these up-front and real-time shares, a compromise between memory and computational load can be deduced, depending on the resource situation, for example for the navigation device. If it is necessary to save storage space, a more computation-intensive (up to a purely real-time-based) calculation of the fluctuation measure can be selected; If, on the other hand, it is necessary to reduce the computational load, then a more memory-intensive computation (up to a purely preprocessed computation) can be carried out.

In addition, the selected subset of the map data may be defined relative to a region of the topographical region to be rendered (eg, to be displayed) based on a measure addition to the region to be rendered. The Maßzugabe can z. B. 25% of the area to be reproduced. This development may be suitable to z. B. solve the problem of a real-time adaptation of the height scale.

In one implementation, the variance is determined based on averaging. If an average value is mentioned here and later, generally a variety of mathematical methods can be used for averaging.

For example, the step of determining the height scale may further include: defining an average of elevations in the z-direction from N height values for the subset of the topographical region, where N ≥ 2; defining the amount of fluctuation based on the mean value (eg, as an average of N deviations of the N height values from the mean value in the z-direction for the subset of the map data); and adjusting, for the subset, the height scale in the z-direction of the topographical region based on the fluctuation value. Alternatively, the step of defining the mean value may include taking N height values from the subset; Adding up all N altitude values; and dividing the result by the number N.

The step of defining the fluctuation measure may be calculating a variance as a quotient whose dividend is the sum of the squares of the differences between the mean and the N height values and whose divisor is the number N; and calculating the variance as the standard deviation, which is the square root of the variance. Further, the step of defining the fluctuation amount may include calculating the fluctuation amount as a quotient whose dividend is the sum of the amounts of the differences between the mean value and the N height values and whose divisor is the number N. In addition, the N altitude values may be values above sea level or normal altitude. All these further developments can be taken alone or in any combination suitable for a naturalistic and at the same time clear presentation of the subset.

According to one variant, the subset is defined by a cluster in a map database. Under a cluster is understood in the context of digital map data, a record for a predetermined geographical region.

The region may be repeatedly selected (eg, continuously) based on a position signal. Further, the digital model for the newly selected region may be repeatedly recreated (eg, contiguously). The position signal may be generated locally by a position sensor (eg, a GPS sensor) or received by an external device (eg, wirelessly).

In addition, the method may include the step of displaying the generated digital model on a display device. The display can be performed together (eg superimposed) with a route calculated by the navigation device.

According to a development of the method according to the invention, the method is carried out by a navigation device. The navigation device may be portable or permanently installed (eg in a vehicle). For example, a portable navigation device may take the form of a mobile phone, a notebook, a music player (MP3 player), and so on.

The invention also provides a computer program product with program code sections for performing the method according to the invention when the computer program product is executed on one or more computer devices. The computer program product may be recorded on a computer readable recording medium.

Furthermore, the invention provides an apparatus for generating a digital three-dimensional model for a topographical terrain from digital map data for a navigation device, wherein the model uses a length scale in the x / y direction and a height scale in the z direction and wherein the device comprises a selection means arranged to select a topographic region defined by a subset of the digital map data; determining means arranged to determine a height scale for the selected topographical region based on a fluctuation measure indicative of height variation in the z-direction for the selected topographical region; and generating means arranged to generate a digital model for at least a portion of the selected topographic region based on the determined height scale and a predetermined length scale.

The device may further comprise a display device for displaying the generated digital model and / or a position sensor. Furthermore, the device can be integrated in a navigation device.

Brief description of the drawings

The accompanying drawings show embodiments of the invention, to which, however, the present invention is in no way limited. In the drawings, like reference numerals designate the same or similar functional blocks or steps. It should be noted that the presentation of individual functional blocks or steps does not preclude the possibility that the respective underlying functionality may be implemented on multiple devices or in multiple steps. Show it:

1 a navigation device according to an embodiment of the present invention;

2 a method according to an embodiment of the present invention; and

3 an Isohöhenlinardarstellung with exemplary qualitative height scales or fluctuation.

Detailed description

1 shows an embodiment of a device according to the invention 101 in the form of a navigation device. It should be noted, however, that the device 101 can also be implemented as a conventional computer.

The device 101 includes a core functionality 1011 that z. At least one CPU (central processing unit) or microprocessor, as a dedicated circuit (eg, as an application specific integrated circuit (FPGA) or field programmable array logic (FPGA) in any implementation) or as a software module can be implemented. Furthermore, the device comprises 101 a memory 1012 , an optional transmitter 1013 and an optional receiver 1014 for the communication of the device 101 with another device (not shown) or with the user. Furthermore, the device comprises 101 a selection device 1015 , a determination device 1016 , a generating device 1017 and, in its embodiment as a navigation device, a display device 1018 and a GPS sensor 1020 ,

In the storage room 1012 Cartographic data are stored in a database in a conventional format. Optionally, the database may further assign a suitable and pre-calculated height scale to each of a plurality of predefined topographic regions (each being defined by a subset, eg, a cluster, of the cartographic data).

Like the dashed extension of the core functionality 1011 is indicated, all of the above-mentioned devices, which are shown within the dashed lines, can be implemented both as stand-alone devices and as sub-functionalities of the core functionality. All of the above devices that overlap the dashed area may be affected by the core functionality 101 can be controlled or the core functionality 101 Provide information.

2 shows a method according to the invention, which is fully or partially the above-mentioned device 101 or their facilities can serve. As in 2 shown includes a communication environment 102 in which the method is performed, the (navigation) device described above 101 ,

In step S1, z. B. the selection device 1015 a topographic region defined by a subset of the digital map data. This selection can z. In real-time to an input by the user or to a signal from the position sensor 1020 happen. Alternatively, the selection can also be done offline, z. When creating or updating the database in memory 1012 ,

In step S2, the determination device determines 1016 a height scale for the selected topographic region based on a measure of variance indicative of height variation in the z-direction for the selected topographic region. It should be noted that the height scale determined in step S2 both directly to the subsequent step S3 (or the generation device 1017 ) can be provided as well as for later use z. In the database in memory 1012 can be stored. In the latter case, the subset can be defined by a cluster in the map data.

In order to determine the height scale, an average value (μ) of N height values (N ≥ 2) from the subset of the map data is formed in step S2, the N altitude values z. B. from a coordinate network of the subset with a step size of z. B. 10 ^-4 degrees longitude and 10 ^-4 degrees latitude can be removed. The mean obtained in this way can serve as the basis for determining a static standard deviation (as the square root of the variance), or it can be processed to a less compute-intensive fluctuation value: Fluctuation value = (Σ | μ (N height values) - HW _N |) / N for all altitude values HW.

The height scale resulting from the fluctuation amount (eg from the standard deviation) may be values z. From 0.5 to 5, the values relating to the ratio to the linear scale. A height scale of 2 is thus twice as chosen as a given length scale. Represents the subset z. If, for example, it is a section of a mountain (eg the Alps), then a scaled scale of 1 results in a realistic representation. For example, a 3-scale elevation scale results in For example, to increase the visibility of smaller bumps in a generally flat area that would be barely visible at a 1 scale. For example, a hill of 100 m relative height, which is located on a high plateau 5000 m high, appears in a similar way to a hill, which is at an absolute height of 20 m.

In step S3 generates z. B. the generating device 1017 a digital model for at least a portion of the selected topographic region based on the determined height scale and the predetermined length scale.

Finally, in an optional step S4, the display device shows 1018 the digital model created in this way. The display may be combined (eg superimposed) with one from the navigation device 101 Route calculated in conventional way. The region can be continuously updated based on an updated GPS sensor position signal 1020 newly selected and continuously recreating and displaying the digital model for the newly selected region.

3 shows an iso-height line representation with exemplary qualitative height scales or fluctuation measures. As in 3 is shown, by dynamically adjusting the height scale in relation to the fluctuation amount, the representation as a result becomes independent of the absolute height. In one area 301 with a rather low absolute height but higher fluctuation, a smaller height scale can be used. On the other hand, in a region having a large absolute height but a low fluctuation amount, a larger height scale is generated.

The presented terrain, which is emphasized in the manner described, also counteracts the subjective perception of the user: on the one hand it avoids that some areas are not visible at all, on the other hand it avoids that the displayed terrain is over-emphasized or covers a displayed route ,

Claims (20)

A method for generating a digital three-dimensional model for a topographical terrain from digital map data, in particular for a navigation device, wherein the model uses a linear scale in the x / y direction and a z-direction vertical scale, comprising the steps: Selecting (S1) a topographic region defined by a subset of the digital map data; Determining (S2) a height scale for the selected topographical region based on a measure of variance indicative of height variation in the z-direction for the selected topographic region; and Generating (S3) a digital model for at least a portion of the selected topographic region based on the determined height scale and a predetermined length scale. The method of claim 1, wherein the height scale is determined using a database that assigns a height scale to each of a plurality of predefined topographic regions, and wherein each height scale is based on an amount of variance pre-calculated for the associated region. The method of claim 1, wherein for determining the height scale, the fluctuation amount is calculated in real time. A method according to claim 1 or 2, wherein for determining the height scale, the fluctuation amount is calculated in advance. Method according to one of the preceding claims, wherein for determining the height scale, the fluctuation amount to a first portion is calculated in advance and calculated to a remaining second portion in real time. The method of claim 5, wherein the first portion indicates a variation measure per region and / or rasterization, and the second component indicates a refinement of the pre-calculated fluctuation measures for a current topographic region. The method of claim 5, wherein the first fraction is the number of polygons per at least one of region and rasterization, and the second fraction is a refinement of the pre-computed variability measures for the topographic region. The method of claim 1, wherein the step of determining the height scale comprises: defining an average of elevations in the z-direction from N height values for the subset of the digital map data, where N ≥ 2; Defining the amount of fluctuation based on the mean; and selecting, for the subset, the height scale in the z-direction of the topographical region based on the fluctuation value. The method according to claim 8, wherein the fluctuation amount is defined as an average of N deviations of the N height values from the mean value in the z-direction. A method according to claim 8 or 9, wherein the N height values are values above normal zero or normal altitude. A method according to any one of claims 8 to 10, wherein the step of defining the fluctuation measure comprises: Calculating the fluctuation measure as a quotient whose dividend is the sum of the amounts of the differences between the mean and the N elevation values and whose divisor is the number N. Method according to one of the preceding claims, wherein the subset is defined by a cluster in a map database. A method according to any one of the preceding claims, further comprising the step of displaying (S4) the generated digital model on a display device. The method of any one of the preceding claims, wherein the region is repeatedly reselected based on a position signal and the digital model is repeatedly recreated for the newly selected region. Method according to one of the preceding claims, carried out on a navigation device. A computer program product having program code portions for carrying out the method according to at least one of the preceding method claims, when the computer program product is executed on one or more computer devices. The computer program product of claim 16 recorded on a computer readable recording medium. Contraption ( 101 ) for generating a digital three-dimensional model for a topographical terrain from digital map data, in particular for a navigation device, wherein the model is used for a length scale in the x / y direction and a height scale in the z direction, comprising: a selection device ( 1015 ) configured to select a topographic region defined by a subset of the digital map data; a determination device ( 1016 ) arranged to determine a height scale for the selected topographical region based on a fluctuation amount indicative of height variation in the z-direction for the selected topographical region; and a generating device ( 1017 ) arranged to generate a digital model for at least a portion of the selected topographic region based on the determined height scale and a predetermined length scale. Apparatus according to claim 18, further comprising a display device ( 1018 ) for displaying (S4) the generated digital model. Navigation device comprising the device according to claim 18 or 19 and a position sensor ( 1020 ).

Images