12 Generating a `trajr` Route From the Telemetry Data

With a large number of points available, we can cast the dataset directly to a trajr route.

The trajr R package was originally developed for use analysing animal tracks, but it’s also really handy for analysing rally routes…

telemetry_full_trajectory = function(telem_df_full){
  
  utm_telem_full = st_transform(telem_df_full,
                                crs=utm_proj4_string) %>% 
                      mutate(lat = st_coordinates(.)[,1],
                             lon = st_coordinates(.)[,2])

  trj <- TrajFromCoords(utm_telem_full %>% select(lon, lat, utc),
                        xCol="lon", yCol="lat", timeCol="utc")
  
  # We assume that the first location is the first location on the route
  trj$distance = Mod(trj$displacement)
  
  trj$cum_dist = cumsum(trj$distance)
  
  trj$speed  = telem_df_full$speed
  trj$brk  = telem_df_full$brk
  trj$throttle  = telem_df_full$throttle
  trj$rpm  = telem_df_full$rpm
  
  trj$lon  = telem_df_full$lon
  trj$lat  = telem_df_full$lat
  
  trj$accx = telem_df_full$accx
  trj$accy = telem_df_full$accy
      
  trj$driver =  telem_df_full$driver
  trj$stage =  telem_df_full$stage

  trj
}

The data includes:

lat/lon coordinates;
a sample timestamp;
speed in km/h;
throttle and brk (brake) as percentage values;
rpm revs;
accx and accy acceleration forces.

If we plot these values against the distance into stage, generated from the location data and cross-referenced to the nearest point on the official stage route, we can generate an idealised basis for comparison between different drivers. However, given that drivers typically follow a very similar line, and hence complete a similar distance over the stage, using their actual distance into the route should provide a reasonable, if approximate, basis for comparison most of the time.

The trajr route actually calculates a distance into the route assuming an origin based on the first point in the route.

evans_fn="df_telemetrymergeddata_SS7_Evans.csv"
trj_evans = telemetry_full_trajectory(get_full_telem(file.path(path, evans_fn)))

ogier_fn="df_telemetrymergeddata_SS7_Ogier.csv"
trj_ogier = telemetry_full_trajectory(get_full_telem(file.path(path, ogier_fn)))

breen_fn="df_telemetrymergeddata_SS7_Breen.csv"
trj_breen = telemetry_full_trajectory(get_full_telem(file.path(path, breen_fn)))

12 Generating a trajr Route From the Telemetry Data

12 Generating a `trajr` Route From the Telemetry Data