Geolocalization with LM based on Traccar service

--======================================================================================================
--*********************************** INTEGRATION WITH TRACCAR PLATFORM ******************************--
--************************* Version 1.0 Created by Sławomir Budzyński 11-11-2016 *********************--
--======================================================================================================
 
traccar = {
  update = function()
  -- load required modules
http = require("socket.http")
mime = require("mime")
ltn12 = require("ltn12")
json = require('json')
 
-- edit parameters
-- server account
login = 'login'
password = 'password'
 
-- UTC zone of Logic Machine e.g. 1 or -1
utc = 1
 
-- Daylight Saving Time e.g. true or false
dst = true
 
-- sending request to Traccar server
t = {}
r, c, d, e = http.request {
  url = "http://demo.traccar.org/api/positions/",
  headers = { authorization = "Basic " .. (mime.b64(login .. ':' .. password)) },
  sink = ltn12.sink.table(t)
}
 
if (c ~= 200) then
  alert("traccar auth error")
  return
end
 
-- decoding received data
response = table.concat(t)
response = json.decode(response)
 
if (type(response) ~= 'table') then
  alert("traccar decode error")
  return
end
 
-- compare the time from last data received from client to now
date = response[1].fixTime
d = {}
d.year, d.month, d.day, d.hour, d.min, d.sec = date:match('(%d+)-(%d+)-(%d+)T(%d+):(%d+):(%d+)')
d.hour = d.hour + utc
if dst == true and os.date("*t")[istdst] then d.hour = d.hour + 1 end
time = os.time(d)
 
-- how much second elapsed from the last data received from a client
delta = os.microtime() - time
 
last_delta = storage.get('Traccar_Last update', 100000)
 
-- update GAs when thera was some update from client or update the 
if delta < last_delta then
storage.set('Traccar_Last update', delta)
grp.update('Traccar_Last update', delta)
grp.update('Longitude', response[1].longitude)
grp.update('Latitude', response[1].latitude)
grp.update('Speed', response[1].speed)
grp.update('Altitude', response[1].altitude)
else
storage.set('Traccar_Last update', delta)
end
  end,
 
  howfar = function( from, to )
  if from.latitude == nil or from.longitude == nil or to.latitude == nil or to.longitude == nil then
    return nil
  end
  local dlat = math.rad(to.latitude-from.latitude)
  local dlon = math.rad(to.longitude-from.longitude)
  local sin_dlat = math.sin(dlat/2)
  local sin_dlon = math.sin(dlon/2)
  local a = sin_dlat * sin_dlat + math.cos(math.rad(from.latitude)) * math.cos(math.rad(to.latitude)) * sin_dlon * sin_dlon
  local c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
  -- 6378 km is the earth's radius at the equator.
  -- 6357 km would be the radius at the poles (earth isn't a perfect circle).
  -- Thus, high latitude distances will be slightly overestimated
  -- To get miles, use 3963 as the constant (equator again)
  local d = 6378 * c
  return d
end,
 
  tocoordinates = function(name)
    if traccar.locations[name] then
      return traccar.locations[name].longitude, traccar.locations[name].latitude
    end
    return nil
  end,
 
  locations = {
  home = {longitude = 23.170, latitude = 50.983},
  work = {longitude = 22.968, latitude = 51.246},
}
  }

-- Read the data from the traccar server
 
traccar.update()