Method for the transformation of position information into a local coordinates system

Abstract

A method for the transformation of information relating to at least one position on a globe from a first global coordinates system into a second local coordinates system, where the position in the first global coordinates system is provided by information relating to the longitude and a latitude, and the position in the second local coordinates system is provided in terms of two axes arranged orthogonally to one another. The method includes receiving a signal containing information relating to the position by means of an antenna, determining a first distance (x) between the position and a reference longitude for the first local axis using a calculation unit, and determining a second distance (y) between the position and a reference latitude for the second local axis by means of the calculation unit. The reference longitude is selected in such a way that it is near to the position.

Claims

1. A method for transforming information relating to at least one position of a vehicle on a globe from a first global coordinates system into a second local coordinates system as the vehicle is moving, the method comprising: receiving, at data recorders supported by the vehicle, a signal containing information relating to a global position of the vehicle in the first global coordinates system having a longitude and a latitude, the signal received from at least one of a GNSS position module or another road user by way of vehicle-to-vehicle communication; selecting, at a calculation device in communication with the data recorders, a reference longitude near the global position; determining, at the calculation device, a first distance (x) between the global position and the reference longitude; selecting, at the calculation device, a reference latitude; determining, at the calculation device, a second distance (y) between the global position and the reference latitude; and determining, at the calculation device, a local position of the vehicle in the second local coordinate system, the local position includes a first local axis and a second local axis arranged orthogonally to one another, the first distance (x) being a first coordinate of the position of the vehicle for the first local axis and the second distance (y) being a second coordinate of the position of the vehicle for the second local axis; wherein the reference latitude and/or the reference longitude is fixed for an application period of time, the application period of time adjusted as a function of a vehicle speed.

2. The method according to claim 1, wherein the reference latitude is near the global position.

3. The method according to claim 1, further comprising: calculating the distance for the first local axis using the equation:
x_P=r*(_P_R)*cos(_P), where r is the earth radius, _P is the longitude of the position, _R is the reference longitude, and _P is the latitude of the position.

4. The method according to claim 3, further comprising: calculating the distance for the first local axis using the equation
x_P=r*(_P_R)*cos(_R).

5. The method according to claim 4, further comprising: calculating the distance for the second local axis using the equation:
y_P=r*(_P_R), where r is the earth radius, _P is the latitude of the position, and _R is the reference latitude.

6. The method according to claim 5, further comprising using the equator as the reference latitude such that the distance for the second local axis is calculated using the equation y_P=r*_P.

7. The method according to claim 1, further comprising: calculating the first distance (x) and the second distance (y) in radians.

8. The method according to claim 1, further comprising: determining a vehicle position; selecting the longitude of the vehicle position as the reference longitude.

9. The method according to claim 8, further comprising: selecting the latitude of the vehicle position ego position as the reference latitude.

10. The method according to claim 1, wherein the application period of time is shorter than 120 seconds.

11. The method according to claim 1, further comprising: linking, at the calculation device, application-specific data with the local position, the application-specific data includes road-related weather data.

12. A vehicle system for transforming information relating to a vehicle position on a globe from a first global coordinates system into a second local coordinates system, the vehicle system comprising: a receiver receiving position signals of the vehicle in a global coordinate system, the position signals include a global position of the vehicle having a longitude and a latitude; and a calculation unit for: selecting a reference longitude near the global position; determining a first distance (x) between the global position and the reference longitude; determining a second distance (y) between the global position and a reference latitude; and determining a local position of the vehicle in the second local coordinate system, the local position includes a first local axis and a second local axis arranged orthogonally to one another, the first distance (x) being a first coordinate of the position of the vehicle for the first local axis and the second distance (y) being a second coordinate of the position of the vehicle for the second local axis; wherein the reference latitude and/or the reference longitude is fixed for an application period of time, the application period of time adjusted as a function of a vehicle speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail below with reference to an embodiment example and figures, wherein:

(2) FIG. 1 shows an exemplary representation of multiple positions in a local coordinates system,

(3) FIG. 2 shows a representation of a transformation of a point P in accordance with the method according to the invention (not to scale), and

(4) FIG. 3 shows a schematic block diagram of a vehicle system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

(6) FIG. 1 shows a scenario in which the method according to the invention is being used. It shows a vehicle 1 which is driving along a road 2 and which detects multiple positions P_1 to P_6 at regular intervals along the road. Each of these positions P_1 to P_6 has been detected by means of a GNSS receiver onboard the vehicle. However, it is also conceivable that such positions are also transmitted by other road users. This fact is immaterial for the method according to the invention.

(7) The positions are originally encoded in accordance with WGS-84 and contain information about the longitude and the latitude. Each of these points may therefore be mapped on the globe on the basis of the information, as shown in FIG. 2. The points P_1 to P_6 are transformed in the ego-vehicle into a second local coordinates system for V2X applications. In FIG. 1, the current position P_0 of the ego-vehicle is indicated as the point of origin of the local coordinates system, which however only constitutes one example. Depending on the application, the point P_0 may also be retained over a certain period of time or application period regardless of whether the ego-vehicle continues moving or not. The transformed local coordinates may be used in order to generate, for example, a region 3 by means of multiple points P_1 to P_6. V2X-relevant information may then be stored for this region 3 such as, for example, road-related weather data. In this way, drivers following the vehicle could be warned about icy roads or other hazards.

(8) The method according to the invention is described in more detail, by way of example, for the point P from FIG. 2. In order to transform the position information regarding point P into a two-dimensional coordinates system, a reference longitude and a reference latitude are initially fixed. The reference latitude _R is, as a general rule, the equator. The reference longitude _R is advantageously stipulated in such a manner that it is located near to the respective position P. The longitude _0 and the latitude _0 of the position of the ego-vehicle P_0 could also be used as the reference longitude _R and the reference latitude. The distance between the current position P and the reference longitude in the alignment of the latitude should advantageously be less than 10 km, particularly preferably less than 1 km, for the applications in a vehicle system.

(9) In order to calculate the local x-coordinate, the distance between the reference longitude _R and the point P is calculated in accordance with the following equation
x_P=r*(_P_R)*cos(_P)

(10) where

(11) r is the earth radius,

(12) _P is the longitude of the position,

(13) _R is the reference longitude, and

(14) _P is the latitude of the position.

(15) In this case, the radius in accordance with the WGS-84 standard may be taken as the radius, according to which standard the radius is 6371000.8 m. In this way, the distance for the x-coordinate is obtained in meters. If the longitude _0 of the position P_0 of the ego-vehicle is taken as the reference longitude, _0 is to be used instead of _R in the above equation.

(16) The distance from the reference latitude _P to the point P is calculated in an appropriate manner, which then corresponds to the y-coordinate. If the equator is taken as the reference latitude, the equation is as follows:
y_P=r*_P

(17) and the distance of the point P from the equator in meters is obtained in this way. If the latitude _0 of the position of the ego-vehicle is taken as the reference longitude, the equation is as follows:
y_P=r*(_P_0).

(18) In this way, all points P_1 to P_6 may be calculated. If the position of the ego-vehicle P_0 is chosen as the point of origin of the local coordinates system, the resulting y-coordinate of the points P_1 to P_6 would be the difference from P_0. The advantage of this is that the values for the y-coordinates are relatively small and, in the event of a limited bit number, for example 32-bits, the local y-coordinates may still be precisely mapped despite the limited bit number. In particular, the calculation is simplified by inserting the latitude _0 of the ego-position into the cosine term during the determination of the x-coordinate, so that the equation
x_P_i=r*(_P_i_0)*cos(_0)

(19) is applied with a constant cos(_0) for P_1 to P_6.

(20) As a result, the invention has substantial advantages, compared with the known method from the prior art, in that the distance between the position and the reference longitude and the reference latitude is calculated based on the difference of the angles (in radians) of the spherical coordinates. In addition, the distortion error is further decreased by means of a suitable selection of the first reference longitude near to a current position.

(21) The reverse transformation of position information from a local coordinates system into a global coordinates system is accordingly carried out by means of an algebraic solution of the aforementioned equations according to the longitude and latitude _P and _P respectively:

(22) Longitude by means of
_P=x_P/(r*cos(_P))+_R

(23) or
_P=x_P/(r*cos(_R))+_R

(24) and latitude by means of
=y_P/r

(25) or
=y_P/r+_R

(26) wherein _R and _R may also correspond to the coordinates of the ego-position _0 and _0.

(27) FIG. 3 shows a vehicle system 10 for the transformation of information relating to at least one position on a globe from a first global coordinates system into a second local coordinates system, wherein the position in the first global coordinates system is provided by means of information relating to the longitude and a latitude, and wherein the position in the second local coordinates system is provided in terms of two axes arranged orthogonally to one another. The aforementioned method is executed by means of the vehicle system 10 described here, so that the particulars of the method itself will not be dealt with in greater detail.

(28) The vehicle system 10 comprises an application block 20 which is connected by means of multiple interfaces 12 with other components of the vehicle and which is shown summarized in FIG. 3 as its own component block 30.

(29) The component block 30 comprises multiple receivers for receiving position signals. Firstly, the system contains a message receiver 31 for receiving messages from other road users. In addition, there is at least one GNSS position module 32 for determining position data of the ego-vehicle.

(30) The application block 20 accordingly comprises data recorders 21, 22 which initially record the data transmitted by the message receiver 31 or GNSS position module 32. The data recorder 21, 22 is designed in such a manner that it only records the transmitted data. Alternatively, the transformation of the coordinates could already take place in the data recorders 21, 22. In the former case, the transformation could also take place in a calculation unit 23 which links the local position data with application-specific data. In the latter case, the data recorders 21, 22 themselves are to be understood to be calculation units.

(31) A message transmitter 24 is also part of the application block 20, by means of which the messages generated by the calculation unit 23 may be transmitted by means of corresponding components 34 for sending messages to other road users. Prior to dispatching the messages, a reverse transformation of the local position information into a global coordinates system, e.g. the WGS-84 format, takes place as described above. This reverse transformation may also similarly take place directly in the message transmitter or in the calculation unit 23.

(32) The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.