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GPS Segment data-frame objects

GPS Segments are represented as data frame objects containing the waypoints of the segment and additional properties about the segment. This document describes the contents of these data frame objects.

Data series

A GPS Segment data frame will contain the following series (note that some of them might not be present). Other parts of the application might add additional data series.

  • lat, lon -- latitude and longitude for each point in the segment
  • geoid -- the geoid (can be computed from lat, lon) -- this is used for matching segments on sessions, among other things.
  • dst -- distance along the segment, in meters. First position has a distance of 0, last position is the total length of the segment.
  • alt -- (OPTIONAL) altitude for each data point, in meters.
  • grade -- (OPTIONAL) the grade, or slope, of the current point as a percentage. Only present if the alt series is present.

To check if a data frame contains some series, use the df-contains? function:

(df-contains? df "lat" "lon" "alt")
=> #t

Properties

The data frame object can store a set of properties, which are key - value mappings. The following properties are present in the gps-segment data frame, while other parts of the application can attach additional properties:

  • total-ascent, total-descent -- total amount of climb and descent along the segment, in meters. Only present if the alt series is present.
  • min-elevation, max-elevation -- lowest and highest altitude point, in meters. Only present if the alt series is present.
  • segment-length -- the total length of the segment, in meters
  • segment-height -- the altitude difference between the start and end of the segment, in meters. Only present if the alt series is present.
  • segment-grade -- the average grade of the segment, calculated as segment-height / segment-length. Only present if the alt series is present.
  • max-grade -- maximum grade in the grade series, if that series is present.
  • fiets-score -- FIETS score, used for climb segments, see climbs.md for what this is and how it is calculated.

Properties can be accessed using the df-get-property function. For example, this will return the segment height, or #f if the property is not present:

(df-get-property df 'segment-height)