GPS filter algorithm
A method for determining location such as vehicle location receives data at a predetermined frequency, validates the received data, stores the received data based on the validation and computes a location based on the stored data. The validation includes verifying a presence of particular data substrings within the received data, verifying a presence of a plurality of data fields within each data substring, computing a parameter based on information contained in two of the plurality of data fields and comparing the computer parameter with a pre-defined threshold.
1. A method for determining vehicle location comprising:
receiving data at a predetermined frequency;
validating the received data;
storing the received data based on the validation; and
a processor computing a location based on the stored data, wherein the validation further comprises:
verifying a presence of particular data substrings within the received data, said substrings including at least one of a GSA substring and a RMC substring;
verifying a presence of a plurality of data fields within each data substring including fields representing at least a horizontal dilution of precision and a vertical dilution of precision;
computing a probability factor by adding the horizontal dilution of precision and the vertical dilution of precision; and
validating the probability factor by comparing the computed probability factor with a pre-defined threshold, wherein the probability factor is valid if it is less than the pre-defined threshold.
2. The method of claim 1 , further comprising receiving the data at a central station remote from the vehicle.
3. The method of claim 1 , further comprising:
designating the received data as invalid data if the computed probability factor is greater than or equal to the pre-defined parameter threshold.
4. The method of claim 3 , further comprising:
measuring a time lapse since a storage of a last data; and
overwriting the last stored data with the last stored data if the time lapse is less than a pre-defined time threshold.
5. The method of claim 4 , further comprising:
triggering a notification that a signal is not being received if the time lapse is equal to or greater than the pre-defined time threshold.
6. The method of claim 1 , wherein the RMC substring includes fields representing at least latitude, longitude and time.
7. The method of claim 1 , wherein storing the received data comprises storing sixteen discrete data strings.
8. The method of claim 7 , further comprising receiving the data strings at one second intervals.
9. A system for determining vehicle location, the system comprising:
a modem for receiving data;
a processing means processor for determining validity of the received data and determining the vehicle location; and
a memory for storing validated data, wherein
the processor
verifies a presence of particular data substrings within the received data, said substrings including at least one of a GSA substring and a RMC substring;
verifies a presence of a plurality of data fields within each data substring including fields representing at least a horizontal dilution of precision and a vertical dilution of precision;
computes a probability factor, by adding the horizontal dilution of precision and the vertical dilution of precision; and
validates the probability factor by comparing the computed probability factor with a pre-defined parameter threshold, wherein the probability factor is valid if it is less than the pre-defined threshold.
10. The system of claim 9 , wherein the processor verifies receipt of data corresponding to a NMEA-0183 standard.
11. The system of claim 9 , wherein the processor compares the computed probability factor with the pre-defined threshold stored in the memory.
12. The system of claim 9 , wherein the modem receives data from an electronic control unit of a vehicle.
13. The method of claim 1 , wherein the received data is a NMEA-0183 data string.
14. The method of claim 1 , further comprising:
storing the received data if the probability factor is valid.