Tiêu chuẩn iso 17572 1 2008

Microsoft Word C045960e doc Reference number ISO 17572 1 2008(E) © ISO 2008 INTERNATIONAL STANDARD ISO 17572 1 First edition 2008 12 15 Intelligent transport systems (ITS) — Location referencing for g[.]

General terms

2.1.1 accuracy measure of closeness of results of observations, computations or estimates to the true values or the values accepted as being true

2.1.2 area two-dimensional, geographical region on the surface of the earth

NOTE An area can be represented as an implicit area or an explicit area

2.1.3 area location two-dimensional location, representing a geographical region on the surface of the earth

2.1.4 attribute characteristic property of an entity like a real-world feature

The identification of a feature is achieved through the sum of its attributes, which have defined types and contain specific values Attributes can be classified as simple, consisting of a single atomic value, or composite, which are made up of multiple values.

2.1.5 coordinate one of an ordered set of N numbers designating the position of a point in N-dimensional space

2.1.6 complex intersection intersection that consists at least of two or more junctions and one or more road elements

2.1.7 composite attribute complex attribute attribute consisting of two or more atomic values and/or attributes

2.1.8 datum set of parameters and control points used to accurately define the three-dimensional shape of the earth

NOTE The corresponding datum is the basis for a planar coordinate reference system

2.1.9 descriptor characteristic of a geographic object, usually stored in an attribute

EXAMPLE Road names or road numbers

This International Standard aims to align with the ISO/TC 211 family of Geographic Information Systems standards, and includes a comparison of terms and definitions in Annex D.

Copyright International Organization for Standardization

2.1.10 digital map database structured set of digital and alphanumeric data portraying geographic locations and relationships of spatial features

Digital maps often represent the electronic version of traditional hard copy maps For instance, drawings can be imported into a Geographic Information System (GIS) and treated as a type of digital map.

2.1.11 dynamic location reference location reference generated on-the-fly based on geographic properties in a digital map database

2.1.12 explicit area two-dimensional face on the surface of the earth, with a specified outline either being a simple geometric figure or an irregular outline/polygon

2.1.13 face two-dimensional element bounded by a closed sequence of edges not intersecting themselves

NOTE The face is the atomic two-dimensional element

2.1.14 implicit area selection of road segments to be referenced belonging to a certain area (subnetwork)

NOTE One implicit area can be built up of multiple subnetworks that are geographically connected

ITRF realization of the ITRS

NOTE The ITRF94 reference frame is consistent with WGS84 at the 5 cm level, and therefore is equivalent to WGS84 for ITS applications

The International Terrestrial Reference System (ITRS) is a geodetic framework for the Earth, established through precise space geodesy measurements beyond just GPS Doppler data This system is regularly monitored and updated by the International Earth Rotation Service to ensure its accuracy.

2.1.17 intersection crossing and/or connection of two or more roads

In GDF, an intersection is defined as a Level 2 representation of a junction that encompasses a road or ferry This intricate feature consists of multiple Level 1 junctions, road elements, and enclosed traffic areas Unlike GDF, the location referencing system in this context pertains to real-world objects rather than a database definition.

NOTE 2 Crossings can be at-grade or grade-separated Crossings that are grade-separated where no connection between the road segments exist, are excluded from this definition

2.1.18 junction elementary element in the road network, connecting two or more road elements

In GDF terminology, a Level 1 feature defines a road element or ferry connection Real crossings are represented by trivalent junctions, which connect three roads A bivalent junction is only applicable when there is an attribute change along the road, such as a change in road name Additionally, junctions are used to mark the end of dead-end roads.

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2.1.19 linear location location that has a one-dimensional character

2.1.20 link edge direct topological connection between two nodes that has a unique link id in a given digital map database

NOTE A link may contain additional intermediate coordinates (shape points) to better represent the shape of curved features A link may be directed or undirected

2.1.21 link identifier link id identifier that is uniquely assigned to a link

A link identifier can be either arbitrary or conventionally assigned to ensure that each identifier is unique within a single instance of a network or map database.

2.1.22 link location location identifiable by a part of the road network database having one identifier or having a uniquely identifiable combination of attributes throughout the continuous stretch

NOTE One link location can consist of multiple links

2.1.23 location simple or compound geographic object to be referenced by a location reference

A location in a database is defined by location definitions that clarify its meaning, typically representing a linear stretch in the network topology without loops or discontinuities It can also refer to a single point, which is a specialized case of a linear stretch with zero length Additionally, a location may encompass a set of road elements that define an area, which can be represented by a polygon or a collection of linear locations For more details on various location categories, see section 5.4.

2.1.24 location definition actual delineation of exactly what is meant (and, therefore, what is not meant) by a particular location within a specific database

The precise definition of the location of a database object or a set of database objects is crucial For instance, the GDF road elements constitute a specific instance of an ALERT-C Location.

2.1.25 location reference reference label which is assigned to a location

A single Location Reference Model (LRM) ensures that one reference distinctly identifies a specific location within the location referencing system This reference serves as a data string exchanged among various implementations of the location referencing system to accurately pinpoint the location.

LRM methodology of assigning location references to locations

LRS complete system by which location references are generated, according to a location referencing method, and communicated, including standards, definitions, software, hardware, and databases

2.1.28 matching translating a location reference to a specific object in a given map database to attempt recognition of the same identified object in both the sender's and the receiver's map database

NOTE Matching is seen as a subsequent part to the method of decoding a location reference adhering to the defined LRM

2.1.29 node zero-dimensional element that is a topological junction of two or more edges, or an end point of an edge

A node is established at key topological points, including basic road intersections and other linear features like boundaries Additionally, nodes are designated for important locations such as electric beacons, kilometre-posts, and traffic flow sensors, all of which are significant points marked on a map.

2.1.30 node identifier identifier assigned to a node

A node identifier can be either arbitrary or conventionally assigned to prevent duplicate identifiers within a single network or across similar networks and databases.

2.1.31 outlined area explicit area with an outline defined by segments being either polylines or linear locations

2.1.32 point zero-dimensional element that specifies geometric location

NOTE One coordinate pair or triplet specifies the location

2.1.33 point location location that has a zero-dimensional character

2.1.34 precision exactness of the measurement of a data value, or of the storage allocated to a measured data value

NOTE Alternatively, the closeness of measurements of the same phenomenon repeated under exactly the same conditions and using the same techniques

2.1.35 pre-coded location reference location reference using a unique identifier that is agreed upon in both sender and receiver system to select a location from a set of pre-coded locations

A quad tree is a hierarchical data structure that divides a specified area into four equally sized quadrants at each lower level Each level of the quad tree maintains awareness of its four sublevels and its parent level.

2.1.37 relationship semantic or topological interrelation or dependency between locations in the LRS

Relationships between locations in the Location Reference System (LRS) are designed to enhance the sophistication of location referencing, often taking on topological or hierarchical structures For instance, a county can be viewed as a collection of multiple city locations, while a lengthy road may consist of several smaller segments This hierarchical approach simplifies referencing, making it more efficient to refer to a county rather than each individual city within it Ultimately, this structure promotes scalability and user-friendliness in LRSs utilizing the Location Reference Model (LRM).

2.1.38 resolution smallest unit which can be represented fixing a limit to precision and accuracy

2.1.39 road part of the road network which is generally considered as a whole and which can be addressed by a single identification like a road name or road number throughout

A road network connection, whether it includes crossings or not, is functionally regarded as a single entity Multiple associated carriageways can be classified as one road, and the term "road" in this context also encompasses the natural language term "street" as defined by ISO 17572.

UML expressions for diagrams

This International Standard employs UML to illustrate particular scenarios, utilizing graphical elements to convey specific constraints and structural relationships For a comprehensive definition, refer to the UML Standard ISO/IEC 19501, while a brief overview of the utilized elements is provided in Annex C.

AGORA Name of a European project 2000-2002 implementAtion of Global lOcation Referencing Approach ALERT-C Advice and problem Location for European Road Traffic-Compact

EVIDENCE name of a European project 1998-1999

Extensive Validation of IDENtification Concepts in Europe GDF Geographic Data File

IETF Internet Engineering Task Force

LR Location Referencing (or Reference)

TPEG Transport Protocol Expert Group

TTI Traffic and Traveller Information

VICS Vehicle Information and Communication System

4 Objectives and requirements for a location referencing method

Objectives for an optimal location referencing method

ITS applications aim for various objectives in location referencing, but these goals often conflict, making complete fulfillment impossible Ideally, an optimal location referencing system would utilize a universally accurate map, allowing for effortless identification of all locations While this ideal is unattainable, the following goals should inform the development and enhancement of any location referencing method, with the specific context of each system influencing the importance of these goals.

The first goal therefore states that processing power in any case is a cost factor to be minimized

O-1 The LRM should be simple enough to be implemented in a resource and performance efficient way

Secondly, location referencing implies at least two systems communicating with each other Communication also causes costs and therefore needs to be minimized

O-2 The LRM should not unduly add to the volume of data to be transferred

The aim to use the exact location, both in the sender and the receiver system, is the reason of referring to it

The receiver is often responsible for interpreting the location reference accurately To facilitate this process, the sending system should provide the location reference with the highest possible precision.

O-3 The LRM should provide location references with the highest accuracy possible.

Requirements of the location referencing method

In addition to the goals, some minimal requirements shall make the different location referencing methods feasible for the foreseen categories of locations (see clause 5.4)

Spatial accuracy is a crucial characteristic of data quality for Intelligent Transportation Systems (ITS) applications, defined in the GDF as the requirement that the shape of a level 0 edge must not deviate from the real shape beyond a specified error margin The accuracy requirements vary based on the specific application and its operational functionality, with advanced vehicle safety systems demanding particularly high precision Additionally, different levels of data accuracy may be necessary within the same application, and these requirements can evolve as technologies and products develop Consequently, the chosen location referencing method for an application is significantly influenced by these spatial data accuracy requirements.

All methods must ensure that they do not introduce additional spatial location errors beyond those already present in the data For area information, such as weather updates or environmental contamination zones, some positional error is acceptable due to the inherently imprecise nature of this data The critical requirement is that these references must be precise enough to enable users to avoid the affected areas or take necessary actions.

An LRM must operate without introducing additional position errors beyond those specified in the reference database It is essential that the location reference is provided with both spatial and temporal accuracy, allowing the vehicle or user to clearly identify the extent of the location.

In certain areas, identifying the side of the road or block where a location is situated is crucial for users For instance, in some road configurations, vehicles and pedestrians may find it challenging to cross to a location on the opposite side without extra routing, while accessing a location on the same side is typically straightforward Thus, it is essential to consider this aspect when providing directions.

R-2 The LRM shall enable referencing of the relative spatial relationship of objects

Location referencing methods must meet functional requirements related to topological relationships, such as determining whether a point is on one side of an object or ensuring that multiple points are arranged in a specific order along a road For locations identified by positions along a logical or physical route, it is essential to maintain the order of points in the reference.

The LRM must maintain the topological relationships among point data without alteration due to its own limitations or deficiencies When referencing geographic coordinates, it is essential that spatial relationships between locations remain clear and are not obscured by imprecision or any other attributes of the referencing system or its functionality.

This International Standard is intended for use in various Location Referencing Systems, with an initial focus on specific categories of locations to optimize the defined Location Referencing Methods.

R-4 The definition of an LRM shall adhere to the common terminology and conceptual model defined in this part of ISO 17572

R-5 The LRM shall provide means to refer only to the categories of Locations explicitly defined by that LRM

R-6 The LRM shall in principle allow addressing of every location on the road network

Location referencing is crucial for traffic telematics and location-based services, as it offers a clear reference for conveying location-specific information This clarity ensures that the location data is machine-readable, allowing equipment to interpret and translate the information into formats that are easily understood by humans, such as mapping positions or providing descriptive directions to a destination.

R-1 The location reference shall be machine-readable

5 Conceptual data model for location referencing methods

Role of conceptual model

The conceptual model serves as a framework for describing and defining a Logical Reference Model (LRM) in broad, conceptual terms It is applicable beyond the specific LRMs outlined in ISO 17572, allowing for the inclusion of various examples to demonstrate the foundational conceptual perspective For additional details, refer to Annex B.

Components of conceptual model

All location referencing methods have some form of the following components The detailed definition of the terms is left to Clause 2

An attribute enables the Location Reference System (LRS) to effectively process and assess location information By distinguishing the reference, attributes ensure that the receiving system can accurately identify the specific location.

A location within the road network is designated for identification, with the sender system designed to reference it while the receiver system seeks to locate it in its map database.

The definition of a location refers to its precise delineation within a digital map database It's important to note that the location definition in a sender system may differ from that in a receiver system, even when referring to the same physical location.

The reference is the label which is assigned to the location

Relationships to other locations in the LRS are also used to support the use of locations in an LRM

Not all Location Reference Models (LRM) require relationships and attributes; for instance, a Location Referencing System (LRS) that assigns arbitrary numbers to locations may not need to define their interrelations However, an LRS that adheres to specific requirements—such as flexibility, extensibility, and compactness—may inherently include relationships within its referencing procedures For example, in RDS-TMC systems, while locations are assigned arbitrary numbers, the referencing system's use of an "extent" allows each location to define its position relative to others, indicating which location is "before" or "after" it.

Description of the conceptual model

A reference is a label assigned to a specific location within a Linear Referencing System (LRS), ensuring each location is uniquely identifiable Locations, which can be simple or compound geographic objects, are linked to database entries through location definitions that clarify their meaning These locations can encompass various attributes that aid in processing and evaluating related information Additionally, relationships between different locations enable more advanced applications of location references, such as establishing topological or hierarchical structures, reflecting the potential for ordered or unordered associations among multiple locations.

Figure 1 — Diagram of conceptual model of LRM

Location categories

Locations shall be categorised as Point Locations, Linear Locations and Area Locations These Location Categories represent real world objects which can be described as follows:

⎯ Existing at a single position (Point Location)

⎯ Between two positions within intersections as road section (Linear Location, in terms of one or more Link Locations)

⎯ Between two positions as road segment (Linear Location)

⎯ Consisting of two or more Link Locations (Linear Location)

⎯ A selection of road segments belonging to a defined collection (subnetwork or collection of subnetworks) (Implicit Area Location)

⎯ Within the boundaries of a defined area (Explicit Area Location)

Point Locations refer to specific positions, such as points of interest and public service facilities Link Locations are linear entities defined by two Point Locations, while Linear Locations consist of multiple consecutive Link Locations, connected by three or more Point Locations that form a continuous stretch in the road network Implicit Area Locations combine several Linear Locations into a single entity, whereas Explicit Area Locations represent two-dimensional features like governmental administrative areas, postal districts, and telephone exchange districts, or simply defined outlines on a map.

Specific reference Object Instance Classes within these Categories are:

⎯ General points - points that may or may not lie on a road network, including points where a road crosses administrative boundaries or borders of map grid cells

⎯ Points at nodes in a topological network representation of roads and their intersections

⎯ Links defined by two consecutive intersections of roads (road sections)

⎯ Points along links bounded by intersections of roads

⎯ Manoeuvres defined by two consecutive links (therefore, three intersections)

⎯ Areas defined by a sequence of Points

⎯ Areas defined by a sequence of link locations

⎯ Areas defined by an origin point and attributes such as the radius of a circle around the point or offsets defining a bounding box

Important location categories for Intelligent Transportation Systems (ITS) databases include man-made structures such as road crossings and road segments, as well as sequences of these segments essential for maneuver descriptions These location categories can be organized into class/type hierarchies to facilitate communication between different receiver and sender systems.

Conceptual model of road network

Location Referencing serves to identify specific segments of the road network To clarify the various terms and their interconnections, a conceptual model of the road network is illustrated in Figure 2 This clarification is essential, as the complex definitions of roads and intersections in GDF do not fulfill the needs of a conceptual model for effective location referencing.

The road network is primarily composed of roads, each identified by a unique name or number Roads are made up of various sections, which can include multiple segments A road section is defined by nodes and edges, bounded by intersections, and may contain intermediate intersections where the road name remains unchanged An intersection serves as a connection or crossing point between roads, with the simplest form being a single node, known as a junction More complex intersections involve multiple nodes and edges.

Refers to parts and/or whole

Figure 2 — Conceptual model for the physical road network

Conceptual model of area locations

An area is a two-dimensional geographical region on the Earth's surface, characterized by specific location referencing constraints based on application requirements The nature of these applications dictates whether to reference the entire geographical figure or a specific number of roads within the area To facilitate Location Reference Model (LRM) handling and establish rules for both explicit and implicit area types, the conceptual model defines relevant terms and describes their containment.

In certain situations, it is possible to explicitly define an area using a geometric figure, while in other instances, it may be necessary to implicitly identify the area by selecting a list of road elements that encompass it.

An implicit area is formed by one or more subnetwork locations, each comprising at least two aggregated road segments In contrast, an explicit area is defined by a geometric function that specifies a region of the Earth's surface, while an area with a freely defined shape is referred to as an outline Both area types have at least one reference connection to the surface, enabling the decoding system to accurately position the specified area.

Outlined area Simple geometric area

Road Segment Geometric Figure Point Location Road Segment

Area topological connection topological connection

Figure 3 — Conceptual model of areas

Inventory of location referencing methods

Road locations can be referenced in two main ways: through attributes of the road network, such as linear distances or street addresses, known as indirect references, or through a coordinate system that divides space independently of the road network, like US UTM coordinates or geographic latitude and longitude.

Indirect referencing methods in network analysis can focus on either the topology of networks, such as Link ID and Linear Referencing, or the attributes of network features, like Cross Street Offset Matching and street addresses Geographic coordinates provide a direct expression of location within the geodetic reference framework, represented as measurements that can be depicted in continuous vector fields (e.g., longitude/latitude) or as quantized subdivisions (e.g., quad trees) Figure A.1 demonstrates both indirect referencing methods, particularly the Link-ID approach, and coordinate referencing methods, specifically the use of Geographic Coordinates.

Figure A.1 — Indirect (Link-ID) vs Geographic Coordinate Schemes

The following list summarizes location referencing methods in use today, which will be discussed briefly in the following sections:

⎯ Referencing by link ID or node ID

A.2 Referencing by link ID or node ID

Logical links illustrate the topological connectivity between nodes that correspond to real-world locations, such as intersections The real-world network can be depicted in the dataset as either a planar or non-planar graph, with the key distinction being whether the links cross without nodes To accurately represent road geometry between intersections, shape points are often inserted between nodes Each link in the network is assigned a numeric identifier known as a link ID, which can be referenced in multiple ways.

⎯ non-unique within a hierarchical scheme, or

⎯ derived from some manipulation of location, such as the bit interleaving of end-node coordinates Two modes of referencing are:

The Unique Link ID serves as a distinct identifier for a link, which may represent a single direction or include an additional identifier for the reverse direction, allowing the link to be either directed or undirected.

⎯ End Node IDs - The link is then identified by two identifiers, those of the link start node and end node

A Link ID reference can include various details, such as offsets from start and end nodes, street side indicators for points of interest, and implied directionality for unique Link-ID references The Link ID LRM is associated with a pre-defined database of identifiers, classifying it as a pre-coded LRM.

A location on the Earth's surface is defined by coordinates within a coordinate system, which includes axes, an origin, and values, along with a geodetic datum that establishes the reference framework (such as ITRF) Coordinate systems can be earth-centered or local, geodetic or planar, and can specify positions in horizontal, vertical, or both dimensions Geodetic parameters play a crucial role in this definition.

Geographic coordinates referencing is outlined in ISO 19111:2007, which focuses on spatial referencing by coordinates, and is further detailed in the updated ISO 6709 standard, which specifies the representation of latitude, longitude, and altitude for geographic point locations.

The dynamic Linear Referencing Model (LRM) is characterized by a coordinate system that operates independently of the road network's locations, allowing for on-demand generation of location codes This feature is particularly useful for accurately determining the position of real-world objects within the geodetic system.

A grid or raster scheme involves dividing a surface into finite, typically rectangular shapes and assigning coordinates in a systematic manner, such as using letters A-Z for columns and numbers 1-10 for rows To enhance data set efficiency and facilitate manipulation through divide-and-conquer algorithms, hierarchical tessellations recursively subdivide surfaces into regular groupings of shapes that are hierarchically numbered These data sets maintain information only where it exists, creating a hybrid approach between continuous field representations and grids Additionally, the grid is defined independently of the road network, classifying it as a dynamic location referencing method (LRM).

A linear referencing method is a technique for pinpointing locations on a network by using known positions of spatial objects This method focuses on the road network, utilizing distances from established nodes or other significant points to define locations Sub-methods such as mile point or reference point employ road labels and distance measures, while mile markers and addressing methods incorporate physical features into the digital base map Due to its dependence on predefined identifiers, this approach is classified as a pre-coded linear referencing method, even though certain reference elements, like offsets, may vary across different references.

Linear Referencing is covered in the ISO/TC 211 Geographic Information Standards, specifically in Section 6.6 of ISO 19133, which focuses on location-based services for tracking and navigation This standard provides essential classes and types for defining linear reference systems Additionally, it is connected to the work of the U.S National Cooperative Highway Research Program, as detailed in NCHRP Report 460, which offers guidelines for implementing multimodal transportation location referencing systems.

The Cross Streets Method identifies nodes using the names of intersecting streets, requiring three street names and offsets from the first intersection to pinpoint a location on a link By including two intersecting street names, an intersection is established, while a third street name indicates two intersections along the same road, defining a specific road segment Offsets further specify positions along the link for points of interest or sub-links The coordinates of the center-line intersection help resolve ambiguities that may arise from using street names alone This Location Referencing Method (LRM) precedes the dynamic location referencing method outlined in part 3 of the International Standard Although it is dynamic, as the reference creation rules are independent of real-world information, it heavily relies on the existence of predefined street names in encoders and decoders To address this limitation, the method has been enhanced with additional information types to reduce dependence on street names For more details on dynamic location referencing, refer to part 3.

Tiêu đề	Intelligent Transport Systems (Its) — Location Referencing For Geographic Databases — Part 1 General Requirements And Conceptual Model
Trường học	International Organization for Standardization
Chuyên ngành	Intelligent Transport Systems
Thể loại	tiêu chuẩn
Năm xuất bản	2008
Thành phố	Geneva

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