Positioning device and method to determine a position using an absolute positioning system and a relative positioning system, computer program and a data carrier

Abstract

A positioning device is arranged to determine a position using an absolute positioning system and a relative positioning system. The positioning device is arranged, in at least one embodiment, to work in a first mode, in which the position is determined using the absolute positioning system and possibly the relative positioning system, and in a second mode, in which the position is determined using the relative positioning system and possibly the absolute positioning system. In the first mode the absolute positioning system is weighted more heavily than in the second mode and the positioning device is arranged to switch from the first to the second mode. The positioning device has access to a digital map database in at least one embodiment and the switch from the first to the second mode is decided based on at least the determined position in combination with information stored in the digital map database.

1 . Positioning device arranged to determine a position using an absolute positioning system and a relative positioning system, the positioning device being arranged to work
 in a first mode, in which the position is determined using at least one of the absolute positioning system and the relative positioning system, and   in a second mode, in which the position is determined using at least one of the relative positioning system and the absolute positioning system, in the first mode the absolute positioning system being weighted relatively more heavily than in the second mode to determine the position, and the positioning device being arranged to switch from the first mode to the second mode, the positioning device at least one of comprising and having access to a digital map database, and the switching from the first to the second mode being decided based on at least the determined position in combination with information stored in the digital map database.   
     
     
         2 . Positioning device according to  claim 1 , wherein the absolute positioning system is one of a satellite based positioning system and a terrestrial positioning system. 
     
     
         3 . Positioning device according to any  claim 1 , wherein the relative positioning system is at least one of a gyroscope, an accelerometer, a compass, a velocity measurement module, a distance meter, an inclinometer and a module detecting steering actions of a steering wheel. 
     
     
         4 . Positioning device according to  claim 1 , wherein the information stored in the digital map database comprises a plurality of geographical objects having threshold distances associated with them. 
     
     
         5 . Positioning device according to  claim 4 , wherein the positioning device is arranged to compute at least one distance from the determined position to a selection of the plurality of geographical object, wherein threshold distances are associated with the plurality of geographical objects, and wherein the switch from the first to the second mode is made if at least one of the at least one computed distance is below a respective associated threshold. 
     
     
         6 . Positioning device according to  claim 2 , wherein the absolute positioning system is arranged to determine a position based on signals received from a plurality of transmitters which are part of the satellite based positioning system or the terrestrial positioning system. 
     
     
         7 . Positioning device according to  claim 6 , wherein the digital map database is a three dimensional digital map database, wherein the information comprises three dimensional information about geographical objects, and wherein the positioning device is arranged to compute a quality of a position as determined by the absolute positioning system based on at least one of the determined position, the position of the transmitters and the three dimensional digital map database. 
     
     
         8 . Positioning device according to  claims 6 , wherein the positioning device is arranged to determine the respective positions of the transmitters based on position information comprised by the respective signals. 
     
     
         9 . Positioning device according to  claim 1 , wherein a further switch from the second to the first mode is decided based on a determined position in combination with information stored in the digital map database. 
     
     
         10 . Positioning device according to  claim 1 , wherein the positioning device is arranged to maintain a history file comprising previously determined positions and associated accuracies as determined according to the absolute positioning system and, when a switch is made from the first mode to the second mode, the positioning device is arranged to select a starting position for the relative positioning system from the history file. 
     
     
         11 . Positioning device according to  claim 1 , wherein the positioning device is arranged to determine accuracies of determined positions in one mode, compare the determined accuracy of positions with a threshold value and in case the accuracy is below the threshold value, and store these positions as a geographical object with an advised mode associated with it, the advised mode being different from the one mode. 
     
     
         12 . Method for determining a position, comprising:
 determining a position using an absolute positioning system and a relative positioning system, the position being determinable   in a first mode, in which the position is determined using at least one of the absolute positioning system and the relative positioning system, and   in a second mode, in which the position is determined using at least one of the relative positioning system and the absolute positioning system, in the first mode the absolute positioning system being weighted relatively more heavily to determine the position than in the second mode;   deciding whether or not to switch from the first mode to the second mode based the determined position in combination with information stored in a digital map database; and   switching from the first mode to the second mode if it is decided to switch.   
     
     
         13 . Method according to  claim 12 , wherein the absolute positioning system is one of a satellite based positioning system and terrestrial positioning system. 
     
     
         14 . Method according to  claim 12 , wherein the relative positioning system is at least one of a gyroscope, an accelerometer, a compass, a velocity measurement module, a distance meter, a module detecting steering actions of a steering wheel, and an inclinometer. 
     
     
         15 . Method according to  claim 12 , wherein the information stored in the digital map database comprises a plurality of geographical objects including associated threshold distances. 
     
     
         16 . Method according to  claim 15 , further comprising:
 computing at least one distance from the determined position to a selection of the plurality of geographical objects having associated threshold distances, the switching from the first to the second mode being done if at least one of the computed distances is below a respective associated threshold.   
     
     
         17 . Method according to  claim 12 , wherein the absolute positioning system APS) is arranged to determine a position based on signals received from a plurality of transmitters being part of the satellite based positioning system or the terrestrial positioning system. 
     
     
         18 . Method according to  claim 17 , wherein the digital map database is a three dimensional digital map database, and the information comprises three dimensional information about geographical objects, the method further comprising:
 computing a quality of a position as determined by the absolute positioning system based on at least one of the determined position, the position of the transmitters and the three dimensional digital map database.   
     
     
         19 . Method according to  claim 17 , further comprising:
 determining the respective positions of the transmitters based on position information comprised by the respective signals.   
     
     
         20 . Method according to  claim 12 , further comprising:
 keeping a history file comprising previously determined positions and associated accuracies as determined according to the absolute positioning system and the relative positioning system, and   selecting, upon the switch is made from the first mode to the second mode,   a starting position for the relative positioning system from the history file.   
     
     
         21 . Method according to  claim 12 , further comprising
 determining accuracies of determined positions in one of the first and second mode;   comparing the determined accuracy of positions with a threshold value; and   storing, in case the comparison indicates that the accuracy is below the threshold value,   the positions as a geographical object with an associated advised mode, the advised mode being different from the one of the first and second modes.   
     
     
         22 . Computer program, which when loaded on a computer arrangement, is arranged to perform the according to  claims 12 . 
     
     
         23 . Data carrier, comprising the computer program according to  claim 22 . 
     
     
         24 . Positioning device according to  claim 2 , wherein the relative positioning system is at least one of a gyroscope, an accelerometer, a compass, a velocity measurement module, a distance meter, an inclinometer and a module detecting steering actions of a steering wheel. 
     
     
         25 . Method according to  claim 18 , further comprising:
 determining the respective positions of the transmitters based on position information comprised by the respective signals.   
     
     
         26 . Computer readable medium comprising program segments which, when executed on a computer device, perform the method of  claim 12 .