conflation.md

Conflation

Overview

• conflation of semantic attributes from OpenStreetMap to lanelet map based on results of matching
• visualization of agreement between amount of lanes in OpenStreetMap and adjacent lanes in lanelet map
• removal of lanelet fragments if they are likely to be mapped wrongly

1. Attribute transfer

• allowed participant and speed limit in lanelet2 inferred from lanelet attributes subtype and location
• relevant combinations shown in table below (taken from lanelet2)

subtype	location	Description	Inferred participants	Speed limit
road	urban	A part of a road in urban region	All vehicles and bikes	City speed limit
road	nonurban	A part of a road in nonurban region	All vehicles and bikes	Nonurban speed limit
highway	urban	A part of a highway in urban region	All vehicles	Urban highway limit
highway	nonurban	A part of a highway in nonurban region	All vehicles	Nonurban highway limit
play_street		A part of a play street	Vehicles, bikes, pedestrians	play street speed limit
bus_lane	urban	Lane for busses	Bus, Emergency, Taxi	City speed limit
bus_lane	nonurban	Lane for busses	Bus, Emergency, Taxi	Nonurban speed limit
bicycle_lane		A lane that is usable only for bikes	Bikes	Average bike speed

• highway tag from OpenStreetMap Wiki used to infer attributes subtype and location according to following custom mapping:

highway	Description OSM Wiki	subtype	location
motorway	A restricted access major divided highway, normally with 2 or more running lanes plus emergency hard shoulder. Equivalent to the Freeway, Autobahn, etc..	highway	nonurban
trunk	The most important roads in a country's system that aren't motorways. (Need not necessarily be a divided highway.)	highway	nonurban
primary	The next most important roads in a country's system. (Often link larger towns.)	road	urban
secondary	The next most important roads in a country's system. (Often link towns.)	road	urban
tertiary	The next most important roads in a country's system. (Often link smaller towns and villages)	road	urban
unclassified	The least important through roads in a country's system – i.e. minor roads of a lower classification than tertiary, but which serve a purpose other than access to properties. (Often link villages and hamlets.)	road	urban
residential	Roads which serve as an access to housing, without function of connecting settlements. Often lined with housing.	road	urban
motorway_link	The link roads (sliproads/ramps) leading to/from a motorway from/to a motorway or lower class highway. Normally with the same motorway restrictions.	highway	nonurban
trunk_link	The link roads (sliproads/ramps) leading to/from a trunk road from/to a trunk road or lower class highway.	highway	nonurban
primary_link	The link roads (sliproads/ramps) leading to/from a primary road from/to a primary road or lower class highway.	road	urban
secondary_link	The link roads (sliproads/ramps) leading to/from a secondary road from/to a secondary road or lower class highway.	road	urban
tertiary_link	The link roads (sliproads/ramps) leading to/from a tertiary road from/to a tertiary road or lower class highway.	road	urban
living_street	For living streets, which are residential streets where pedestrians have legal priority over cars, speeds are kept very low and where children are allowed to play on the street.	play_street
service	For access roads to, or within an industrial estate, camp site, business park, car park, alleys, etc. Can be used in conjunction with service=* to indicate the type of usage and with access=* to indicate who can use it and in what circumstances.	road	urban
road (unknown type)	A road/way/street/motorway/etc. of unknown type. It can stand for anything ranging from a footpath to a motorway. This tag should only be used temporarily until the road/way/etc. has been properly surveyed. If you do know the road type, do not use this value, instead use one of the more specific highway=* values.
busway	A dedicated roadway for bus rapid transit systems	bus_lane	urban
cycleway	For designated cycleways. Add foot=*, though it may be avoided if default-access-restrictions do apply.	bicycle_lane

• additionally, the following attributes are transferred to their counterparts:
  • transfer of maxspeed tag to lanelet2 speed_limit tag
  • transfer of name tag to lanelet2 road_name tag
  • transfer of surface tag to lanelet2 road_surface tag
  • transfer of oneway tag to lanelet2 one_way tag
  • transfer of lane_markings tag to lanelet2 lane_markings tag
• attribute transfer realized based on stored lanelets in the collapsed centerlines from the preprocessing step
• if the value of an attribute in OpenStreetMap changes over a match, the corresponding lanelets are splitted
• images below show principle of simple attribute transfer and the special case of an attribute change during a match {height=150px}
  {height=150px} {height=150px}

2. Evaluation of Adjacent Lanes

• sum up the amount of adjacent lanelets in the lanelet map

• compare to lanes attribute from OpenStreetMap (also considering the attribute shoulder and incrementing the amount of lanes, if necessary) and colorize lanelets correspondingly

• image below shows the process for the evaluation
  

  • lanes tag = amount of adjacent lanelets => green
  • lanes tag != amount of adjacent lanelets => red
  • no lanes tag => blue
  • no match for polyline => white

• if lanes or shoulder change over a match, the process is analogous to the attribute transfer (splitting of lanelets)

3. Deletion of Lanelet Fragments

• if for an identified match the lanelet map contains more adjacent lanelets than OpenStreetMap indicates, the package tries to remove wrongly mapped lanelets:
  • as long as there are more adjacent lanelets in the lanelet map than OpenStreetMap indicates, lanelets are removed if they neither have a predecessor nor a successor
  • more steps can be implemented, however, keep in mind that you are absolutely sure if you want to delete something as the information from OpenStreetMap might be wrong as well
• image below exemplarily shows the deletion of an existing lanelet fragment
  {height=300px}