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 10 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 10 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.