getActivityInfo Current Speed Filtering

I'm using the following function to get the current speed.

function getCurrentSpeed() {

        var info = Activity.getActivityInfo();

        return info.currentSpeed;

    }

When the Activity is setup like below:

_activity = Recording.createSession({

            :sport => Recording.SPORT_CYCLING,

            :subSport => Recording.SUB_SPORT_GENERIC,

            :name => "515"

        });

The returned speed value appears to have almost no filtering. It responds to a change in speed very quickly but it's also very noisy.

When the Activity is setup as a running activity like:

_activity = Recording.createSession({

            :sport => Recording.SPORT_RUNNING,

            :subSport => Recording.SUB_SPORT_GENERIC,

            :name => "515"

        });

The returned speed value appears to be smoothed for 30 - 60 seconds.

Is this the intended behavior? Can the smoothing be adjusted?

For my application, the 30-60 seconds is too slow of a response. I don't want to use the CYCLING sport type because then it doesn't record running cadence from the watch accelerometer. What are my options for getting at a less filtered speed value from the GPS?

MoxyRoger over 10 years ago

I worked around the problem by calculating my own speed value from the distance and time values.

This function is called once per second so this gives me about 5 second smoothing but can be easily adjusted. Seems to provide nice feedback on a VivoActive in my initial test. It's easy to change paces to hit a new target.

This way, I can use a RUNNING Activity and also collect the running cadence data.

hidden var _spdSmooth = 5;

    hidden var _distList = new [_spdSmooth + 1];

    hidden var _timeList = new [_spdSmooth + 1];

    hidden var _numValues = 0;



...



	function getCurrentSpeed() {

		var info = Activity.getActivityInfo();

		var speed = null;

		var sumX = 0;

		var sumY = 0;

		var sumXY = 0;

		var sumXX = 0;

		if (info.elapsedDistance != null && info.elapsedTime != null) {  // if they aren't null, add them to the list

			_timeList[_numValues] = info.elapsedTime;

			_distList[_numValues] = info.elapsedDistance;

			_numValues = _numValues + 1;

			

			if (_numValues > _spdSmooth) {								// if the list is full, shift it down

				for (var i = 0; i < _numValues; ++i) {

    				_timeList= _timeList[i + 1];

    				_distList= _distList[i + 1];

    				_numValues = _spdSmooth;

        		}

        	}



			if (_numValues > 1) {										// if we have more than 2 values, try to calculate the slope

				for (var i = 0; i < _numValues; ++i) {

    				sumX = sumX + _timeList;

    				sumY = sumY + _distList;

    				sumXY = sumXY + _timeList*_distList;

    				sumXX = sumXX + _timeList*_timeList;

				}

				if (_numValues * sumXX - sumX * sumX != 0) {

					speed = 1000 * (_numValues * sumXY - sumX * sumY) / (_numValues * sumXX - sumX * sumX);

				}

				else {

					speed = null;

				}

        	}

		}

        return speed;

	}

[/CODE]

Nikeow over 9 years ago

was playing around with the F3 and saw that it also happens on the F3. When running the bike app, the speed is very responsive. But when I use a custom app and do speed, I can see that the speed is very dampened.

Former Member over 9 years ago

How it looks on speed graph? Does it take whole minute to stabilize, like on VA? Some smoothing is expected, just not that much.