Vehicle navigation system and method

An improved vehicle navigation system comprising:

• a map database with map information, said vehicle navigation system derives a map heading from said map information;
• and
• a GPS receiver which provides GPS velocity information including a heading, said vehicle navigation system uses said velocity information to propagate a previous position to a current position and interrogates said map database to obtain said map heading information;
• said vehicle navigation system updates said velocity information with said map heading for propagating said previous position to said current position if the difference between the heading of said velocity information and said map heading are within a threshold, wherein said system projects said velocity onto said map heading and integrating said projected velocity to obtain a displacement and obtaining said current position by applying said displacement to said previous position.

A method of estimating the velocity of a vehicle known to be on a mapped path comprising:

• determining the velocity of the vehicle, the velocity including a heading;
• interrogating a map database to obtain a map heading of said mapped path;
• and
• updating said velocity with said map heading if the difference between the heading of said velocity and said map heading are within a threshold;
• using said velocity to propagate a previous position to a current position, wherein said step of using includes rotating velocity to align with said map heading and integrating rotated velocity to obtain a displacement and obtaining said current position by applying said displacement to said previous position.

A method of estimating the velocity of a vehicle known to be on a mapped path comprising:

• determining the velocity of the vehicle, the velocity including a heading;
• interrogating a map database to obtain a map heading of said mapped path;
• updating said velocity with said man heading if the difference between the heading of said velocity and said map heading are within a threshold;
• and
• using said velocity to propagate a previous position to a current position, wherein said step of using includes projecting said velocity to align with said map heading and integrating said projected velocity to obtain a displacement and obtaining said current position by applying said displacement to said previous position.

A method of propagating a previous position to a current position in a position determination system, said method including the steps of:

• providing longitudinal acceleration information from an orthogonal axes accelerometer;
• providing lateral acceleration information from said orthogonal axes accelerometer;
• determining longitudinal speed from said longitudinal acceleration information;
• deriving heading change from said lateral acceleration information and said longitudinal speed;
• using said heading change and said longitudinal acceleration to propagate a previous position to a current position
• providing GPS velocities;
• determining lateral and longitudinal calibration information from said GPS velocities:
• and
• calibrating said orthogonal axes accelerometer with said lateral and longitudinal calibration information.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• and
• an orthogonal axes accelerometer provides motion signals having longitudinal and lateral acceleration information and zero offsets, said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system compares said motion signals with a threshold to determine a zero motion state, and if said vehicle navigation system is in said zero motion state, said vehicle navigation system determines said zero offsets.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• and
• an orthogonal axes accelerometer provides motion signals having longitudinal and lateral acceleration information and zero offsets, said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system comparing said motion signals with a threshold to determine a zero motion state, and said vehicle navigation system locks heading changes and calibrates said zero offsets if said vehicle navigation system is in said zero motion state.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• an orthogonal axes accelerometer provides motion signals having longitudinal and lateral acceleration information and zero offsets, including longitudinal and lateral acceleration information, said vehicle navigation system determines heading change using said lateral acceleration information and longitudinal speed;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system comparing said motion signals with a threshold to determine a zero motion state, and said vehicle navigation system locks heading changes and calibrates said zero offsets of said orthogonal axes accelerometer if said vehicle navigation system is in said zero motion state;
• an odometer provides displacement information, said vehicle navigation system determines displacement using at least one of said longitudinal acceleration information and said displacement information, said vehicle navigation system determines heading change from said lateral acceleration information, said vehicle navigation system determines odometer calibration information from said GPS velocity information if said GPS velocity information is used, said vehicle navigation system uses said heading change and said displacement to propagate a previous position to a current position if said GPS velocity information is not used;
• and
• a map database which stores map information, said vehicle navigation system determines a heading from said map information, said vehicle navigation system updates said GPS velocity information with said heading before propagating said previous position to a current position.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• an orthogonal axes accelerometer provides longitudinal and lateral acceleration information, said vehicle navigation system determines lateral and longitudinal calibration information from said GPS velocity information to calibrate said orthogonal axes accelerometer if said GPS velocity information is used;
• and
• an odometer provides displacement information, said vehicle navigation system determines displacement using at least one of said longitudinal acceleration information and said displacement information;
• said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change and said displacement to propagate a previous position to a current position if said GPS velocity information is not used;
• and
• a map database which stores map information, said vehicle navigation system determines a map heading from said map information, said vehicle navigation system updates said GPS velocity information with said map heading before propagating said previous position to a current position if the difference between said map heading and the heading of said GPS velocity information is within a threshold.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides which provides GPS delta range information and GPS velocity information calculated from a set of said GPS delta range information, said vehicle navigation system uses said GPS velocity information when said set of GPS delta range information is available and calculates GPS velocity information from a subset of said GPS delta range information when said set of GPS delta range information is not available and uses said GPS velocity information to propagate a previous position to a current position;
• an orthogonal axes accelerometer provides motion signals having longitudinal and lateral acceleration information and zero offsets, said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system comparing said motion signals with a threshold to determine a zero motion state, and said vehicle navigation system locks heading changes and calibrates said zero offsets if said vehicle navigation system is in said zero motion state;
• and
• a map database which stores map information, said vehicle navigation system determines a map heading from said map information, said vehicle navigation system updates said GPS velocity information with said map heading before propagating said previous position to a current position if the difference between the heading of said GPS velocity information and said map heading is within a threshold.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• an orthogonal axes accelerometer provides longitudinal and lateral acceleration information, said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system determines latitudinal and longitudinal calibration information from said GPS velocity information to calibrate said orthogonal axes accelerometer;
• an odometer provides displacement information, said vehicle navigation system determines displacement using at least one of said longitudinal acceleration information and said displacement information;
• said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change and said displacement to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system determines odometer calibration information from said GPS velocity information if said GPS velocity information is used to calibrate said odometer;
• and
• a map database which stores map information, said vehicle navigation system determines a map heading from said map information, said vehicle navigation system updates said GPS velocity information with said map heading if the difference between the GPS heading and said map heading are within a threshold before propagating said previous position to a current position.

An improved vehicle navigation system, comprising:

• a GPS receiver which provides GPS velocity information, said vehicle navigation system uses said GPS velocity information to propagate a previous position to a current position;
• an orthogonal axes accelerometer provides motion signals having longitudinal and lateral acceleration information and zero offsets, said vehicle navigation system determines heading change using said lateral acceleration information;
• said vehicle navigation system uses said heading change to propagate a previous position to a current position if said GPS velocity information is not used, said vehicle navigation system comparing said motion signals with a threshold to determine a zero motion state, and said vehicle navigation system locks heading changes and calibrates said zero offsets if said vehicle navigation system is in said zero motion state, said vehicle navigation system determines lateral and longitudinal calibration information from said GPS velocity information to calibrate said orthogonal axes accelerometer if said GPS velocity information is used if said vehicle navigation is not in said zero motion state;
• and
• a map database which stores map information, said vehicle navigation system determines a map heading from said map information, said vehicle navigation system updates said GPS velocity information with said map heading if the difference between the heading of said GPS velocity information and said map heading is within a threshold before propagating said previous position to a current position.