описание

Area level, Area type:
- speed limit data is divided into rectangular areas
- root area (level 0) is splitted into four rectangular parts (level 1 areas)
- each part (nw/ne/sw/se) may contain limits or further parts (level 2 areas)
- further splitting depends on number of speed limits (not yet investigated)

Latitude, Longitude:
- speed limit position (or end position of limited section)
- coordinate conversion to meters (to compare with covered area)
  xLimit = Longitude*72000
  yLimit = Latitude/9*1000000

Direction:
- northerly direction in degrees, counting clockwise
- range from 0 to 360, with a resolution of 3 degree
- special value of -1 -> any direction

Limit flag:
- describes the type of dataset
  0 -> speed limit dataset (only supported on motorways)
  1 -> speed camera dataset

Speed:
- speed limit value
- range from 10 to 150, needs to be a multiple of 10
- special value of 0 -> dynamic speed limit

Limit mode:
- controls behavior of speed limit display
- range from 0 to 15, meaning depends also on limit flag
  0     -> regular speed limit
  1     -> speed limit depends on the weather or time of day
  4..15 -> length of limited section, (value-1)*100m

Area x, Area y, Area width, Area height:
- only informative data, not necessary for composition
- covered area, origin and dimension in meters
- x grows from Greenwich meridian to east
- y grows from equator to north
- restrictions for speed limit position with respect to covered area
  x <= xLimit < x+width
  y <= yLimit < y+height