Reading a set of gpx files
==========================

# get all file names from some directory

query getDirectory('/home/ralf/Tracks', 2) transformstream filter[not(isDirectory(.Elem))] consume

let Raw =  getDirectory('/home/ralf/Tracks') transformstream 
  filter[not(isDirectory(.Elem))] 
  addcounter[TrackId, 1]
  loopsel[fun(t: TUPLE) gpximport(attr(t, Elem)) 
    projectextend[Time, Lon, Lat, Ele; TrackId: attr(t, TrackId), Pos: makepoint(.Lon, .Lat)]]
  consume

# create Trip and Altitude for each day. Filter out very long connections of two successive 
# points from the raw data.

let twohours = [const duration value (0 7200000)]

let DayTrips =  Raw feed 
  filter[.Lat > 50.0]
  extend_last[Seg: makeline(.Pos, ..Pos)::[const line value undef]] 
  extend[Length: size(.Seg)] 
  filter[.Length < 0.001]
  extend[
    I: .Time + twohours, 
    Alt: .Ele] 
  sortby[TrackId, I asc]
  groupby[TrackId
  ; DayTrip: group feed approximate[I, Pos, [const duration value (0 300000)]],
    DayAlt: group feed approximate[I, Alt, [const duration value (0 300000)]] ]
  consume


# alternative representation: split by trips

let Trips = DayTrips feed 
  projectextendstream[TrackId
  ; Trip: .DayTrip sim_trips[ [const duration value (0 300000)]] ]
  extend[Traj: trajectory(.Trip)]
  consume



# Match all trips

let MatchedTrips = Trips feed addcounter[No, 1] 
  extend[Matched: omapmatchmht(Edges, EdgeIndex_Box_rtree, EdgeIndex, .Trip) aconsume] 
  consume

# 407 seconds
# 169 Trips matched with 41294 units

# 2.4 secs per trip with 244 units per trip