Deep dive: How exactly the Apple Watch tracks swimming

 

The measurement of movement in water is involved. 

Here is how the Apple laptop is compatible.

The built-in accelerometer, gyrocompass and GPS chip help the Apple watch to move in the water.

During the last week, I passed sprayed in an underground university pool with the Apple 3 Clock series. When the company has tragically matured, Apple has marketed more like a machine particularly adapted by a partnership with Nike Racing Mate. But Apple Watch also offers more dynamic and varied things than your morning jogging exercise in the water.

The device works like a SwimTracker since it remained challenged in 2016, but with its latest operating system, it has a more granular measurement: detection kit. He knows when one sits on the edge of the pool, then uses this information to share training sets and will show you the amount of time you swam, the accident and your time off.

You do not need the latest Apple Watch model to get this information. A series 2 running the fourth-generation operating system will work fine. But I swam with the most recent version of the company that comes with a cellular connection. I could make a call by going to the pool without taking my cell phone, but it was the biggest advantage of the latest and best offer.

In the basin, Apple Watch is a tool to quantify the complex movements of any body of water, and as an enthusiast for many years, I was interested in how it works.

           

Apple has built its algorithms to detect the stroke of swimmers of all difficulty levels, as well as the calories they burn. The process involved collecting data from more than 700 swimmers and over 1,500 swimming sessions. Part of this data collection swam in place (in an endless pool) with a mask that came up from the ceiling.

There is a lot of data. And all this data is necessary because the skill level affects the form. "When you are Michael Phelps, you make a big difference between these four strokes - bouncing, freestyle, chest, and tail butterfly," says Jay Blahnik, who directs Apple's fitness and health technology. "If you are me, it turned out that when we look at the gyro and accelerometer signals, we are not so loud and clear." 

 From wrist to satellite

 The watch uses the gyroscope or accelerometer to follow the movement of its strokes, but in the open water, you can use a different sensor: the GPS chip. When you bathe in the ocean or a lake, your watch uses it to determine the speed and distance to travel. But GPS signals do not lead to H2O. Fortunately, it is likely that freestyle people in the open water, and for this accident, their arms regularly cut the surface. Apple defines the GPS chip in capture mode for all swimming. The satellite signal will remain explored every time your hand rises out of the water. "We try to catch it every time," says Ron Huang, Apple's director of engineering for site and process services.

The accelerometer measures the movement, and the gyroscope determines how much the clock rotates per second. Together, these sensors help Apple understand the type of line.

"What we're seeing is the trajectory of his wrist as he does every hit," Huang said. The butterfly and freestyle look like the clock's sensors, which present their biggest "confusion matrix." But it is important that this is correct because the type of attack affects the number of calories burned. The butterfly, for example, can burn 40 percent more calories compared to swimming.

The gyroscope tends to show that the clock is spinning, even if it is not - a phenomenon called gyroscopic. For example, your wrist may be, but the twist can say it rotates 10 degrees per second. In this case, Apple relies on the accelerometer to find the truth on the ground. If the accelerometer shows that it is not moving, but the gyroscope still shows the rotation, you can learn how to read how many gyroscopes.

Turning, turning, turning

Smart swimmers turn as a somersault and turn to reverse direction when they reach the edge of the pool. But not me, not Blahnik, the apple health expert. "If you've ever seen my change, it's not so good, and it's so bad that I do not turn around at all," admits Blahnik. "We had to be very good on the turn, be it a great swimmer or a less experienced swimmer." In different words, no matter how yourself turn, the watch should always notice it.

Here, the Gyro helps. It measures rotation in three different planes in space: around the x, y, z-axes. The abscissa axis is horizontally on the screen; the vertical axis y; and the z triggers the display. Clock software interprets gyro data to know when a wall has been reached and has been rotated 180 degrees in a new direction, such as how selfish greed is a measure of the direction of your nose. For example, keep the wrist flat in front of you and parallel to the ground, and imagine that the z-axis pulls directly into the sky: a rotation around this z-axis indicates a change in direction.

Learning how many strokes it takes to cross the pool, Apple knows when it expects to make a spin. Suppose you usually need about 25 shots, but later in your workouts, Apple notes that it only took 10. You can then deduce that this is likely because you only hang in the middle of the pool, and this should ignore any greed you see, there may be rotated 90 degrees to swing spurious beacons. 

Trust your senses

Perhaps the most interesting decision that Apple has made is to rely on its sensors on board more than one entry for individual users. Before swimming, the watch will ask you to tell you how long the pool lasts, in meters or at the shipyards. But Apple knows there is a good chance that this measurement is incorrect. Perhaps the pool has a length of 25 meters but is said to be 25 meters. "This is the map," Huang said. At the end of your bath, the clock tells you how much you swim, but it depends on the length of your pool. Bath 10 rounds in a pool that says last 25 feet and the clock informs you that swimming at 250 feet. Apple just responds to what you said for this metric. However, the watch does not need to know the length of the pool on its part to accurately count its laps, as it does it independently for knowing the turns.

But most importantly, measuring the distance from the total distance is not important, at least not when it comes to knowing how many calories have stayed smoked. "One thing we remarked is that the number of rounds he's knotted is not an excellent indicator of the actual calories he burned," Huang said.

Think of swimmer who easily crosses the pool with a few bangs, he said. Do not burn as several calories as someone who works to take it to the wall, leaving as many bangs as they do. Therefore, the watch uses its sensors to mark yaw changes when they have completed a turn and directed, and counts their strokes; he uses this information to estimate calorie burning. "We did not just want to go through the tachometer and distance to give him calories; we wanted to measure his swimming efficiency and the number of shots he took," Huang said.