Radionavigation for swimmers
Methods, systems and computer program products for radionavigation for swimmers are described. A mobile device configured to estimate a location using radio frequency signals can estimate a position of the swimmer when the mobile device is worn on a limb of the swimmer and periodically submerged. The mobile device can supply auxiliary information to a radionavigation subsystem to correct a navigation solution affected by limb motion of the swimmer and affected by the periodic submersion of the mobile device.
1. A method comprising:
receiving, by a radio frequency (RF) receiver of a mobile device, RF signals;
determining, by a processor of the mobile device, a velocity of the mobile device based on the RF signals;
receiving, by the processor, sensor data from one or more sensors of the mobile device;
determining, by the processor, an angular speed of a limb of a swimmer wearing the mobile device on the limb, the angular speed determined at least in part from the sensor data;
determining, by the processor, a direction of travel of the mobile device, the direction of travel determined at least in part from the sensor data;
determining a relative velocity based on the angular speed of the limb, an estimated length of the limb, and the direction of travel of the mobile device, the relative velocity being a velocity of the mobile device relative to a torso of the swimmer;
determining, by the processor, a velocity of the swimmer based on a difference between the velocity of the mobile device and the relative velocity; and
presenting, on a display of the mobile device, a representation of at least one of the velocity of the swimmer, a position of the swimmer based on the velocity of the swimmer or a distance traveled by the swimmer based on the velocity of the swimmer.
2. The method of claim 1 , wherein determining the angular speed of the limb is based at least in part on readings of the one or more sensors of the mobile device measuring linear and angular acceleration.
3. The method of claim 1 , wherein determining the angular speed of the limb is based at least in part on readings of the one or more sensors of the mobile device measuring magnetic field and acceleration.
4. The method of claim 1 , wherein determining the angular speed of the limb is based at least in part on readings of a barometer of the mobile device indicating periods that the mobile device is above water.
5. The method of claim 1 , wherein the length of the limb is estimated based on a user input indicating a height of the swimmer.
6. The method of claim 1 , wherein the length of the limb is estimated by learning during a current swim or based on stroke data collected from one or more previous swims.
7. The method of claim 1 , wherein the direction of travel is determined based on the velocity of the mobile device.
8. The method of claim 1 , wherein the direction of travel is determined based on an output from an inertial navigation subsystem of the mobile device.
9. The method of claim 1 , wherein the direction of travel is determined based on geographic data indicating an orientation of a body of water.
10. The method of claim 1 , wherein the distance traveled by the swimmer is determined by integrating the velocity of the mobile device.
11. The method of claim 1 , further comprising instructing the radionavigation subsystem to correct one or more radionavigation observables of the RF signals according to the relative velocity.
12. The method of claim 11 , wherein the one or more radionavigation observables include at least one of a Doppler shift or a carrier phase.
13. A mobile device comprising:
one or more processors; and
a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
receiving, by a radio frequency (RF) receiver of a mobile device, RF signals;
determining, by a processor of the mobile device, a velocity of the mobile device based on the RF signals;
receiving, by the processor, sensor data from one or more sensors of the mobile device:
determining, by the processor, an angular speed of a limb of a swimmer wearing the mobile device on the limb, the angular speed determined at least in part from the sensor data;
determining, by the processor, a direction of travel of the mobile device, the direction of travel determined at least in part from the sensor data;
determining a relative velocity based on the angular speed of the limb, an estimated length of the limb, and the direction of travel of the mobile device, the relative velocity being a velocity of the mobile device relative to a torso of the swimmer;
determining, by the processor, a velocity of the swimmer based on a difference between the velocity of the mobile device and the relative velocity; and
presenting, on a display of the mobile device, a representation of at least one of the velocity of the swimmer, a position of the swimmer based on the velocity of the swimmer or a distance traveled by the swimmer based on the velocity of the swimmer.
14. The mobile device of claim 13 , wherein determining the angular speed of the limb is based at least in part on readings of the one or more sensors of the mobile device measuring linear and angular acceleration.
15. The mobile device of claim 13 , wherein the length of the limb is estimated based on a user input indicating a height of the swimmer.
16. The mobile device of claim 13 , wherein the length of the limb is estimated by learning during a current swim or based on stroke data collected from one or more previous swims.
17. The mobile device of claim 13 , wherein the direction of travel is determined based on the velocity of the mobile device.
18. The mobile device of claim 13 , wherein the direction of travel is determined based on an output from an inertial navigation subsystem of the mobile device.
19. A non-transitory computer-readable medium storing instructions that when executed by one or more processors, cause the one or more processors to perform operations comprising:
receiving, by a radio frequency (RF) receiver of a mobile device, RF signals;
determining, by a processor of the mobile device, a velocity of the mobile device based on the RF signals;
receiving, by the processor, sensor data from one or more sensors of the mobile device:
determining, by the processor, an angular speed of a limb of a swimmer wearing the mobile device on the limb, the angular speed determined at least in part from the sensor data;
determining, by the processor, a direction of travel of the mobile device, the direction of travel determined at least in part from the sensor data;
determining a relative velocity based on the angular speed of the limb, an estimated length of the limb, and the direction of travel of the mobile device, the relative velocity being a velocity of the mobile device relative to a torso of the swimmer;
determining, by the processor, a velocity of the swimmer based on a difference between the velocity of the mobile device and the relative velocity; and
presenting, on a display of the mobile device, a representation of at least one of the velocity of the swimmer, a position of the swimmer based on the velocity of the swimmer or a distance traveled by the swimmer based on the velocity of the swimmer.
20. The non-transitory computer-readable medium of claim 19 , wherein determining the angular speed of the limb is based at least in part on readings of the one or more sensors of the mobile device measuring linear and angular acceleration.