Method for determining a measurable target variable and corresponding system
The invention relates to a method and a system for determining a target variable to be measured in a mobile device. A first physical variable is measured with the aid of a first sensor and a second physical variable with the aid of a second sensor. The second physical variable is different to the first physical variable, or is measured using a different technique. The value of the target variable is calculated with the aid of the measurement of the first and second physical variables. An estimate for the target variable is determined with the aid of at least the measurement of the first physical variable. At least a first error estimate is determined, which depicts the accuracy of the measurement of the first physical variable. The estimate of the target variable is filtered using both the first error estimate and the measurement of the second physical variable.
1. A method for improving the accuracy of a measured physical performance target variable of a user in performing a sporting activity, the method comprising:
measuring a first physical performance variable of the user with the aid of a first sensor positioned within one of a wristop computer, a shoe mounted sensor and a body mounted sensor;
measuring a second physical performance variable of the user with the aid of a second sensor;
calculating a value of the physical performance target variable with the aid of the measurements of the first and second physical performance variables;
determining an estimate for the physical performance target variable with the aid of the measurement of at least the first physical performance variable;
determining at least a first error estimate, which depicts the error in the measurement of the first physical performance variable;
adapting a filter to a filtering strength that corresponds to the magnitude of said at least first error estimate;
filtering the estimate of the physical performance target variable using both the first error estimate and the measurement result of the second physical performance variable; and
displaying a value with an improved accuracy of the physical performance target variable to the user,
wherein the target variable is speed or altitude.
2. The method of claim 1 , wherein the estimate for the target variable is calculated with the aid of the measurement of the first and second physical variable.
3. The method of claim 1 , further including:
determining a second error estimate depicting the error of the measurement of the second physical variable; and
filtering the estimate of said physical performance target variable using both the first and the second error estimates.
4. The method of claim 1 , wherein the strength of the filtering of said physical performance target value is increased when the error estimate of the first and/or second physical variable increases.
5. The method of claim 1 , further including: detecting the rate of change of the target variable; and altering the strength of the filtering in the calculation of the target variable depending on the rate of change of the first and/or second variable.
6. The method of claim 1 , wherein the estimate of the target variable is filtered during a filtering period which length is arranged to adapt to measured changes of the first and/or second physical variable.
7. The method of claim 1 , wherein the first sensor is a satellite-positioning sensor, and wherein the first physical performance variable is the user's speed during the performance of the sporting activity, or absolute or relative location.
8. The method of claim 1 , wherein the first sensor is an atmospheric-pressure sensor, and wherein the first physical performance variable is atmospheric pressure occurring during the performance of the sporting activity.
9. The method of claim 1 , wherein the first sensor is a satellite-positioning sensor, and wherein the first physical performance variable is altitude during the performance of the sporting activity.
10. The method of claim 1 , wherein the second sensor is an acceleration sensor, and wherein the second physical performance variable is user's acceleration during the performance of the sporting activity.
11. The method of claim 1 , wherein the second sensor is a pressure sensor, and wherein the second physical performance variable is atmospheric pressure during the performance of the sporting activity.
12. The method of claim 1 , wherein the method is performed entirely or partly in a mobile telephone.
13. The method of claim 1 , wherein the method is performed entirely or partly in a satellite-positioning module or other device without a display.
14. The method of claim 1 , wherein the method is performed entirely or partly in a portable satellite-positioning device, an outdoor-recreation computer, a yachting computer, or other device with a display.
15. The method of claim 1 , wherein the estimate of the target variable is filtered with the aid of a Kalman filter.
16. The method of claim 1 , wherein the first and the second sensors are based on different measurement techniques that have different error profiles as a function of the measurement frequency.
17. The method of claim 1 , wherein the filtering of the target variable is implemented by determining an error estimate for a computation model that depicts how well the computation model used corresponds to the real situation, with the measurement of at least the measurement of the second physical variable, and filtering the estimate of the target variable at a strength that depends on both the error estimate of the measurement and the error estimate of the said computation model.
18. The method of claim 1 , wherein at least two of the following are located in separate device units, which are arranged to communicate wirelessly with each other:
a first sensor,
a second sensor,
a mechanism for calculating the value of the target variable, and
a device unit, which contains at least one of the said sensors and is arranged to transmit an error estimate of the measure made with the aid of the sensor in question wirelessly to the device unit that comprises the mechanism for calculation the value of the target variable.
19. The method of claim 1 , wherein a selection of at least two alternative types of sporting activities can result in different values which in turn affects the manner of calculation used for the physical performance target variable.
20. A system for improving the accuracy of a measured user's physical performance target variable, the system comprising:
a wristop computer including at least first and second sensors for measuring a first and second physical performance variables, respectively;
a first mechanism configured to:
calculate a value of said physical performance target variable by measurements of said first and second physical performance variables,
determine an estimate for the physical performance target variable with the aid of the measurement of at least the first physical performance variable,
to determine at least a first error estimate, and
adapting a filter to have a filtering strength that corresponds to the magnitude of said at least first error estimate and the measurement result of the second physical performance variable,
a second mechanism configured to filter the estimate of the physical performance target variable using both the first error estimate and the measurement of the second physical performance variable, and
a display for displaying a value with an improved accuracy of the physical performance target variable to the user,
wherein the target variable is speed or altitude.
21. The system of claim 20 , wherein at least two of the first sensor, the second sensor, and the first mechanism are located in first and second separate device units.
22. The system of claim 21 , wherein the first second device unit is a wristop device, and wherein the second first device unit is a portable device with a display.
23. The system of claim 21 , wherein the device unit that contains at least one of the said sensors is arranged to transmit wirelessly an error estimate of the measurement made with the aid of the sensor in question.
24. The system of claim 20 , wherein at least one of the first and second sensors are located in a device unit without a display.
25. The method of claim 1 , wherein a selection of one of at least two alternative types of sporting activities results in the selection of one of at least two available sport activity tracking algorithms.
26. The system of claim 20 , wherein at least one of the first and second physical performance variables is altitude, and wherein the physical performance target variable is vertical speed.
27. The system of claim 26 , wherein the wristop computer determines the user's rate of climb and/or rate of descent.
28. The system of claim 26 , wherein the other of the first and second physical performance variable is user's horizontal speed.
29. The system of claim 20 , wherein the first and second physical performance variables are selected from the group consisting of user's horizontal speed, user's horizontal acceleration, user's altitude, user's vertical speed, and combinations thereof.