Method for monitoring the operation of a global position system receiver
View Patent ↗A method is provided for determining the validity of a signal received by a GPS receiver. A signal that is unfiltered, either mathematically or electronically, is monitored to determine the variability of different occurrences of the signal. These occurrences, which may be sequential, are compared to each other in order to detect whether or not variation exists between one occurrence of the signal and a subsequent occurrence of the signal. If no variation exists, it is determined that the signal is invalid and that a loss of fix of the satellite signal has occurred. If sufficient variability exists in the signal, between successive occurrences, the signal is deemed to be valid and suitable for use to control a vehicle such as a marine vessel.
1. A method for monitoring the operation of a receiver, comprising the steps of:
determining a magnitude of a difference between two occurrences of a first signal;
comparing said magnitude of said difference to a preselected threshold value; and
identifying an operating condition of said receiver as a function of the relative magnitudes of said difference between said two occurrences and said preselected threshold value, wherein said identifying step comprises the step of determining that said receiver is inoperative if the absolute value of said difference is not greater than said preselected threshold value.
2. The method of claim 1 , wherein:
said first signal comprises a plurality of serial occurrences.
3. The method of claim 1 , wherein:
said comparing step comprises the step of subtracting one of said two occurrences from another of said two occurrences to calculate said difference between said two occurrences.
4. The method of claim 1 , wherein:
said two occurrences of said first signal are sequential occurrences.
5. The method of claim 1 , further comprising:
causing an alarm to be generated when said identifying step determines that said difference is less than or equal to said threshold value.
6. The method of claim 1 , wherein:
said first signal is unfiltered.
7. The method of claim 1 , wherein:
said operating condition is the validity of said first signal.
8. The method of claim 1 , wherein:
said receiver is a global positioning system receiver.
9. A method for monitoring the operation of a receiver, comprising the steps of:
receiving a first magnitude of a first occurrence of a first signal;
receiving a second magnitude of a second occurrence of said first signal;
calculating a change between said first and second magnitudes; and
identifying an inoperative condition of said receiver when the degree of change between said first and second magnitudes is less than a preselected threshold value.
10. The method of claim 9 , wherein:
said first and second occurrences are sequential.
11. The method of claim 9 , wherein:
said change is determined as a function of a ratio calculated by dividing said second magnitude by said first magnitude.
12. The method of claim 9 , wherein:
said first signal is a representation of a speed over ground signal provided by a global positioning system receiver.
13. The method of claim 9 , wherein:
said degree of change is a difference calculated by subtracting said second magnitude from said first magnitude.