CSIS Discussion Paper No.142

A Proposal for Lane Level Location Referencing
Satoru NAKAJO*, Ayako MIURA**, Takeshi DOIHARA*, Ryosuke SHIBASAKI**Center for Spatial Information Science, The University of Tokyo
Cw503 4-6-1 Komaba Meguro-ku Tokyo Japan 153-8505
Tel: +81-3-5252-6412 snakajo@csis.u-tokyo.ac.jp**Research Center for Advanced Science and Technology, The University of Tokyo

Abstract
The needs for precise location information exchange is increasing such as for autonomous driving
and for safety application in ITS. Location information exchange in lane level is required broadly. In thispaper, basic concept of a lane level location referencing method is briefly explained. The main concept
explained on this paper is come mainly from the result of discussion between the authors. The purpose ofthis paper is to make a reference for further research and creating a standard within the global level.

Keywords
Location Referencing, Spatial Information Distribution/Exchange, Autonomous Driving

1. Introduction
The needs for location referencing method which can use in lane level is increasing because of
the rapid technological progress in autonomous driving and cooperative systems in ITS. On the other hand,
there are no widely used standard which can execute location referencing within lane level. Based on thesituation above, the authors have decided to create a location referencing method which can use forautonomous driving and cooperative systems within lane level.
In this paper, Constituents of Location Referencing Method are briefly described. The authors
noticed that some of the ideas described in this paper may need further research for realizing an actual use.
2. Constituents of Location Referencing Specification
2.1 Concept of Location Referencing MethodThe basic concept of location referencing method the authors proposing is as described in bellow.
First, the "standard" used when performing location referencing at the lane level is incorporated in aportion of the dynamic map. It does not necessarily have an independent layer for the locationreferencing Method. This means that sharing of this Method by both the information sender andinformation receiver makes it possible to reliably perform location referencing at a level that preventslane errors at a location accuracy of about 25 cm.

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Second, defining the method so as to enable location referencing at each of "straight segments"and "junctions/intersections". This means that when performing location referencing at the lane level, thelocation referencing method used at each road site is presumed to differ. The IDs and locations (profiles) of
roadway links (straight segments) and common reference points (junctions/intersections) will be definedcorresponding to each location referencing method. The aforementioned location referencing method isable to coordinate with geometry as well as topology at the lane level on a dynamic map.
Location referencing infrastructure

Actual feature
CRP1Receiver map

Geometry only

Dynamic map(Topology at lane level)
Common reference point
CRP2

Receiver map

Route/lane level topology(Low accuracy)

Lane levelnetwork
CRP3-1

Lane levelnetwork
CRP3-2

Receiver map

Lane level topology(High accuracy)

Figure 1

Exchange of Information Mediated by Location Reference Method (concept)

2.2 Constituents of Location Referencing Specification
The method needs the components of "links at the roadway level (ID + profile)" + "common
reference points (CRP) of junctions/intersections (etc.)". The brief definitions of each component are asfollows.
Links at roadway level (ID + profile) is that used to express location as "distance traveled fromendpoint" + "lane information" on "straight segments"
CRP (ID + relationship with actual feature + (+ latitude and longitude)) is that used as common
reference points of endpoints of "straight segments" and "junctions/intersections" (road sites where links atroadway level are not present). The CRP has multiple levels.

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CRP present in the location referencing Method is composed of the three levels indicated below.
As a result, together with affixing a point on a map, location information on geometry and topology (roadsection ID system level, roadway level, lane level) can be converted.

CRP Level
CommonReference Point(CRP) Level 1

CommonReference Point(CRP) Level 2

CommonReference Point(CRP) Level 3-1

CommonReference Point(CRP) Level 3-2

Table 1 Definition of CRP (Common Reference Point)
Purpose of Use
Definition
Used to correlate between location
Points obtained from features having thereferencing Method and geometry map
following characteristics:
・Structures exhibiting little change
・Structures detectable from vehicles
using lasers or cameras
Points used as origins (commonPoints obtained virtually generated fromreference points) when representing
points composing CRP level 1.
Correlated with referencing point oflocations at intersections and junctions.
road segment ID system.
Points for correlating between roadsegment ID system, roadway link
endpoints and lane link endpoints.
Points used as origins when representing Network at roadway level composed oflocations on straight segmentsintersection boundary nodes and(intersection boundary nodes), and links roadway links
for specifying applicable roadways(roadway links).

Points used as origins when representing
locations on straight segments(intersection boundary nodes), and links
for specifying applicable lanes (lanelinks).
* Included in dynamic map but not used
for location referencing Method

3Network at lane level composed ofintersection boundary nodes, profile line
nodes and lane links.

2.3 Relationship between CRP levels
CRP are correlated in order from level 1 (actual feature) to level 2 (virtual point) to level 3-1(virtual point (or actual feature)). The relationships between different CRP levels are defined as follows.

Table 2 Method Used to Correlate between CRP level 1 and CRP level 2
Correlation MethodCRPCRPLevel 1

Level 2

* A CRP level 2 point is generated virtually from points composing CRP level 1

Level 1＊ CRP
CRPレベル1

**

*

★ CRP
CRPレベル2
Level 2

**

★
**

CRP

CRP

Level 2

Level 3-1***

(Example 1) Designation of intersection boundary nodes of CRP level 3-1 using polar
coordinates from CRP level 2

CRP Level 2
CRP Level 3-1 (intersection boundary nodes)
CRP Level 3-1(Intersection boundary nodes)★

(Example 2) Generation of correspondence table between points of CRP level 2 andintersection boundary nodes of CRP level 3-1

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2.4 Definitions of CRPs
A proposal for definitions of CRPs is as follows.

Table 3 Definitions of CRP Level 1
Constituent
CommonReference
Point (CRP)
Level 1

InstalledLocation
Straight
segments

Proposed Definition

・Location where road

Road sign

sign column contacts＊CRPレベル1
CRP Level 1*ground・Location in center ofroad sign

*Represented withpositional coordinates*(x,y,h)・Location whereDistance marker (map point)

distance marker
Level 1＊CRP
CRPレベル1

contacts ground・Location in center of
distance marker

*

10km

*Represented with*positional coordinates(x,y,h)・Midpoint of seam

Seams in road bed

・Intersection between*

curb and seam centerline**Intersections

center line

＊CRP
CRPレベル1
Level 1*Intersection between
curb and seam centerline

・Location where road

Road signs

sign column contacts*＊CRP
CRPレベル1
Level 1ground・Location in center ofroad sign*

*Represented withpositional coordinates(x,y,h)5

・Location where light

Traffic signals＊ CRP
CRPレベル1
Level 1

*contacts ground・Location in center oflight*Represented with*positional coordinates(x,y,h)Curb/Median strip＊ CRP
CRPレベル1
Level 1***・Apex of median strip
・Junctions of curb
straight portion andcurved portion*Represented with**positional coordinates(x,y,h)

*

*

*

*

*
・Apex of concrete

Junctions/branches
CRP Level 1

structure installed atback portion of stripedtraffic paint pattern ofjunctions and branches

・Impact absorbers(hard nose)*Represented withpositional coordinates(x,y,h)・Apices of concrete

Toll booths
*
*

*
*

******6★ CRP
CRPレベル1
Level 1structures on islands
that compose tollbooths

Table 4 Definitions of CRP Level 2
Constituent

InstalledLocation

CommonStraight

Reference Pointsegments

Proposed Definition
Generated with polar coordinates from CRP level 1・Designation of polar
coordinates fromLevel 1＊ CRP
CRPレベル1(CRP) Level 2★CRP
CRPレベル2
Level 2points composing
CRP level 1 (distancemarker)

*

10km

*Performed inconjunction with★

*direct retention of
positional coordinatesof CRP level 2 ondynamic map

Planar

Generated as planar center of gravity・(Upper illustration)
Planar center ofintersections***

Level 1＊ CRP
CRPレベル1

gravity generated

Level 2★ CRP
CRPレベル2from points
composing CRP level**1 (curb, median strip)

・(Lower illustration)

★
**

*

Planar center of**gravity generated
from points
composing CRP level
1 (locations of center＊ CRP
CRPレベル1
Level 1
Level 2★ CRP
CRPレベル2*★
*7**

lights of trafficsignals)

Linear

Example 1) Generated as line midpoint 1）

intersections＊ CRP
CRPレベル1
Level 1垂線Verticalline

Level 2★ CRP
CRPレベル2
Midpoint中点★

・(Example 1)
Midpoint of line
connecting midpointsof vertical lines
extending from points(curb) composing
CRP level 1** **・(Example 2)
Example 2) Generated with polar coordinates from

Designation of polar

CRP level 1

coordinates from＊ CRP
CRPレベル1
Level 1
Level 2★ CRP
CRPレベル2*points compositing
CRP level 1 (location
where road signcolumn contacts★

ground or location incenter of road sign*

Junctions/branchessurface)

Example 1) Generated as line midpoint・(Example 1)
Midpoint of verticalline extending from
CRP level 1 (hardnose)＊ CRP
CRPレベル1
Level 1
Level 2★ CRP
CRPレベル2*★

Example 2) Generated with polar coordinates from
CRP level 1・(Example 2)
Designation of polar＊ CRP
CRPレベル1
Level 1

coordinates from★ CRP
CRPレベル2
Level 2

CRP level 1 (hardnose)*★

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Toll booths

・Planar center ofGenerated as planar center of gravity

**

*
*

Level 1＊ CRP
CRPレベル1

gravity generated★ CRP
CRPレベル2
Level 2from points* ★ *****

composing CRP level1

3. Proposal for a location information distribution specification to be standardized
A proposal for a location referencing information distribution specification is shown on bellow.
Use of contents distribution specifications capable of being represented by both latitude andlongitude (geometry) and ID (topology). A location can be represented with either information alone if only
one element is sent. In the case both elements are sent, the receivers use the information that is easier touse corresponding to the objective.
The use of ID is proposed for "straight segments" while the use of latitude and longitude isproposed for "junctions". It is desired to be able to determine whether or not latitude and longitude has beencorrected (map matching) with the location referencing Method in the case of having decided to use
latitude and longitude directly instead of using a method based on common reference points + polar
coordinates (one of the methods stipulated in linear referencing of ISO19148) at junctions and branches (inconsideration of the wide use of position representation according to latitude and longitude).
The method shall have an ability to represent points, lines and planes.
The description of definition of latitude and longitude WGS84 used in GPS will be used for thecoordinate system and coordinates will be processed up to 10-7 significant digits. Although values will
undergo location specification alone, it will be possible to determine whether or not values have beencorrected (map matching) with the location referencing Method (dynamic map).
The description of definition of ID is as follows. Composed of lane link + distance traveled fromend point + lane information (total number of lanes + number of oncoming lanes as viewed from left
in the direction of travel). Lane link ID will be correlated with road section ID method (so as not tochange frequently)

9CRP Level 2

CRP Level 3-1 (intersection boundary nodes)
CRP Level 3-1(Intersection boundary nodes)

Figure 4 Concept of Location Referencing Method

Figure 4 UML of the proposed location information distribution Specification

4. Conclusion
In this paper, the authors briefly discuss the basic concept of lane level location referencing
method. To realize and to be widely used in the world, it shall be necessary to enhance the discussion
between various kinds of experts related to location information and autonomous driving. It shall be needed
to standardize this method officially internationally is also needed.

References1) ISO 17572-1:2015, Intelligent transport systems (ITS) -- Location referencing for geographic databases-- Part 1: General requirements and conceptual model, 2015
2) ISO 17572-2:2015 Intelligent transport systems (ITS) -- Location referencing for geographic databases-- Part 2: Pre-coded location references, 2015103) ISO17572-3:2015 Intelligent transport systems (ITS) -- Location referencing for geographic databases -Part 3: Dynamic location references, 2015
4) ISO 19148:2012 Geographic information -- Linear referencing, 20125) Satoru NAKAJO, -Personal Perspective- Location Referencing for lane level information,
ISO/TC204/WG3 meeting, 13 October 2015 (Personal Access)6) Satoru NAKAJO, Ryosuke SHIBASAKI, Realizing for Lane Level Location Referencing, 13th ITS
Symposium in Japan, 3 December 2015 (Japanese)
7) Ryuichi IMAI, Satoru NAKAJO, Mitsuaki MATSUYAMA, Koichi SHIGETAKA, Minoru ISHIDA andTakahiko HAMADA, Location Referencing Method for Distribution for Various Road Related Data,April. 2012, Journal of Japan Society of Civil Engineers. (Japanese)
8) Kees WEVERS, Transport Network ITS Spatial Data Deployment Platform Purpose, status andprospects, Joint UNECE-Belgium Workshop on ITS, 18 November 201411