[[minLat, minLng], [maxLat, maxLng]], or null for a GPS-less activity.
Distance-grid profiles, one per present channel (elevation first).
Time the clock ran (last sample − first sample).
Recorded laps (device-marked), if the source carried them.
Time actually moving (speed above the stopped threshold).
Douglas–Peucker-simplified [lat, lng] line for the map overview; empty
for a GPS-less activity (no map).
Per-kilometre splits (computed, evenly spaced).
Everything the activity summary holds, computed from one activity's streams.