Read attributes in other samples than GPS data

[wiktorn]

Apart from samples with location information, such as:

    {
      "Attributes": {
        "suunto/sml": {
          "Sample": {
            "GPSAltitude": 91.4,
            "Latitude": 0.31337,
            "Longitude": 0.31337,
            "UTC": "2019-12-30T11:08:45.000+00:00"
          }
        }
      },
      "Source": "suunto-191910002448",
      "TimeISO8601": "2019-12-30T12:08:45.000+01:00"
    },

There are other Samples, containing

• EHPE - Estimated Horizontal Position Error, EVPE - Estimated Vertical Position Error, NumberOfSatellites, Satellite5BestSNR - what is basically quality of GPS/GNSS signal
• AbsPressure, Altitude, Cadence, Distance, Power, SeaLevelPressure, Speed, Temperature, VerticalSpeed - which is data coming from other sensors
• BatteryCharge, BatteryCurrent, BatteryVoltage

It would be nice to include the middle point. The challange here is that they are reported with different timestamps than location data.

And readings from heart beat monitor:

    {
      "Attributes": {
        "suunto/sml": {
          "R-R": {
            "IBI": [
              392,
              410,
              295,
              403,
              322,
              364,
              277,
              335,
              391,
              435
            ]
          }
        }
      },
      "Source": "suunto-191910002448",
      "TimeISO8601": "2019-12-30T12:08:45.580+01:00"
    },

Where IBI stands for "Inter Beat Interval.

The challange here, is that there are multiple samples reported on the same timestamp, which probably needs to be concatenated - as then sum of IBI is close to difference in timestamps. Anyway - IBI data have quite a lot of variation which suggests that this data needs to be cleaned before calculating real BPM.

Data could be then put in either of:

• Garmin trackpoint extension: http://www.garmin.com/xmlschemas/TrackPointExtension/v1 https://www8.garmin.com/xmlschemas/TrackPointExtensionv1.xsd
• Cluetrust trackpoint extension: http://www.cluetrust.com/XML/GPXDATA/1/0 http://www.cluetrust.com/Schemas/gpxdata10.xsd

Please bear in mind, that Garmin extension is more restrictive on allowed values:

• cad values 0-254
• hr values 1-255

[wiktorn]

I've already addressed some of above using pandas to easily join the data along time axis, and fill missing location data, for timestamps, where additional data is available, but no location data was gathered.

I've also tried to do some smoothing of IBI, elimination of extreme values, but haven't succeed in getting the values, that Suunto reports itself. Can share it as a pull request.