mark-p-thomas : Track Splitting

Sections

Introduction

Splitting is the act of breaking up a Track at a Point or Segment. For detailed information on how this is done on the Track Polyline, see the Polyline Splitting page.

• If the splitting occurs at a Point, the Point is duplicated & ends/starts the resulting Tracks.

• If the splitting occurs at a Segment, the Segment is removed & the first Point ends the first Track, while the second Point starts the next Track.

Tracks may need to be split based on different criteria. Some common ones are:

• Stopping one movement, then starting another movement

• Changing activity types during the same recording

• Starting & stopping multiple times on the same track recording before and/or after a movement.

• Cruft

Cases & Considerations

Tracks resulting from a split may be too small to have been intentionally kept, so these should be dropped based on the # of Points contained, length of the Track, or time duration of the Track.

• The # of Points & length are both costly to calculate & are affected by irrelevant variables such as GPS recording intervals & have O(n) time complexity to determine.

• Time duration is more intuitive of a metric for movement to be likely wanted, is unaffected by other variables, & is cheap to calculate, having O(1) time complexity. This is the metric chosen to be used.

Segment Removed		Segments Kept
First		Even
Last		Odd
Middle		Odd
		Drop Start
		Drop End
Example w/ min duration = 2 min

Child Pages

• Splitting by a Single Activity
• Splitting by Multiple Activities