GPS Navigation Velocity Vector Dead Reckoning
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Solution Overview
Problem
Current GPS navigation systems experience a significant delay in providing navigation instructions due to the time required to collect Ephemeris data, which can take up to 30 seconds even with a high signal-to-noise ratio, and this delay worsens when Ephemeris data becomes outdated or unavailable, such as when the device is powered off for an extended period or in areas where GPS-assisted systems are not available.
Innovation Solution
A GPS navigation device that uses a velocity vector derived from an acquired and tracked GPS signal, combined with last stored Ephemeris or Almanac data, to provide navigation features like routing, positioning, and guidance through dead reckoning techniques, allowing immediate navigation services even without current Ephemeris data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the GPS receiver collects current Ephemeris data to provide accurate position and velocity updates, then the navigation accuracy is improved, but the Time-To-First-Fix (TTFF) increases by up to 30 seconds
Solution Approach 1:
The system performs preliminary action by using previously collected Ephemeris data (from before the current session) to immediately provide navigation services when the device is powered on. This allows the GPS receiver to skip the 30-second TTFF delay by retrieving and utilizing stored Ephemeris information from non-volatile memory, thereby providing immediate position and velocity updates without waiting for current Ephemeris collection.
2Loss of time
If the GPS receiver uses stored Ephemeris data from non-volatile memory, then the TTFF is reduced, but the navigation accuracy deteriorates when the stored Ephemeris is outdated
Solution Approach 1:
The system applies dynamics by continuously monitoring the age of stored Ephemeris data and dynamically switching between two operational modes: (1) using stored Ephemeris data when it is relatively recent (providing fast TTFF), and (2) switching to alternative methods when the stored Ephemeris becomes outdated. This dynamic adaptation allows the system to optimize between speed and accuracy based on real-time conditions.
Solution Approach 2:
The system introduces an intermediary mechanism that detects when stored Ephemeris data becomes unreliable and mediates the transition to alternative navigation methods. This intermediary layer ensures that the system can maintain operational continuity by switching between stored Ephemeris usage and other positioning methods, thereby preventing accuracy deterioration from outdated data.
3Measurement precision
If the GPS receiver waits for current Ephemeris data to be collected, then the position and velocity calculations are accurate, but the user must wait at least an extra 30 seconds for guidance instructions
Solution Approach 1:
The system performs preliminary action by utilizing previously collected Ephemeris data stored in non-volatile memory to immediately provide navigation guidance instructions when the device is powered on. This eliminates the 30-second waiting period by retrieving and applying stored Ephemeris information before the user needs navigation instructions, thereby improving ease of operation without significantly compromising accuracy.
4Measurement precision
If the GPS receiver collects Ephemeris data continuously, then the navigation services are always accurate, but the device complexity and energy consumption increase
Solution Approach 1:
The system applies partial action by collecting and storing Ephemeris data periodically rather than continuously, and by using only the necessary portion of stored Ephemeris data (specifically for the current session) rather than maintaining all historical data. This partial approach reduces device complexity and energy consumption while still providing accurate navigation services when needed.
Data Source
AI summary
A navigation device includes a computer platform that includes a global positioning system (GPS) receiver operable to acquire and track a GPS signal, a processor assembly, and a memory. The memory includes at least one of last recorded Ephemeris and Almanac information, and a GPS velocity vector determination module operable to generate a velocity vector output in the absence of current Ephemeris based upon the tracked GPS signal and the last recorded GPS information. A method of vehicle navigation in the absence of current Ephemeris includes acquiring and tracking a GPS signal, retrieving from a memory a last recorded location of a vehicle, setting a dead reckoning startup location equal to the last recorded location, retrieving from a memory at least one of a last recorded Ephemeris and Almanac, determining a current velocity vector and determining a current location based upon the velocity vector and the dead reckoning startup location.