CEN/TR 17448:2020
(Main)Space - Use of GNSS-based positioning for road Intelligent Transport Systems (ITS) - Metrics and Performance levels detailed definition
Space - Use of GNSS-based positioning for road Intelligent Transport Systems (ITS) - Metrics and Performance levels detailed definition
This document constitutes the main deliverable from WP1.1 of the GP-START project. It is devoted to a thorough review of the metrics defined in EN 16803-1 and proposes a performance classification for GNSS-based positioning terminals within designed for road applications. It will serve as one of the inputs to the elaboration of prEN 16803-2:2019 and prEN 16803-3:2019.
This document should serve as a starting point for discussion within CEN/CENELEC/JTC 5/WG1 on a consolidated set of performance metrics and associated classification logic. The proposals and conclusions appearing in this document are therefore only preliminary.
Detaillierte Definition von Metriken und Leistungsstufen
Espace - Utilisation de la localisation basée sur les GNSS pour les systèmes de transport routiers intelligents - Définition détaillée des mesures et niveaux de performance
Vesolje - Uporaba sistemov globalne satelitske navigacije (GNSS) za ugotavljanje položaja pri inteligentnih transportnih sistemih (ITS) v cestnem prometu - Podrobna opredelitev meritev in ravni uspešnosti
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SLOVENSKI STANDARD
01-maj-2020
Vesolje - Uporaba sistemov globalne satelitske navigacije (GNSS) za ugotavljanje
položaja pri inteligentnih transportnih sistemih (ITS) v cestnem prometu -
Podrobna opredelitev meritev in ravni uspešnosti
Space - Use of GNSS-based positioning for road Intelligent Transport Systems (ITS) -
Metrics and Performance levels detailed definition
Detaillierte Definition von Metriken und Leistungsstufen
Espace - Utilisation de la localisation basée sur les GNSS pour les systèmes de
transport routiers intelligents - Définition détaillée des mesures et niveaux de
performance
Ta slovenski standard je istoveten z: CEN/TR 17448:2020
ICS:
03.220.20 Cestni transport Road transport
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
35.240.60 Uporabniške rešitve IT v IT applications in transport
prometu
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL REPORT
CEN/TR 17448
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
March 2020
ICS 03.220.20; 33.060.30; 35.240.60
English version
Space - Use of GNSS-based positioning for road Intelligent
Transport Systems (ITS) - Metrics and Performance levels
detailed definition
Espace - Utilisation de la localisation basée sur les Detaillierte Definition von Metriken und
GNSS pour les systèmes de transport routiers Leistungsstufen
intelligents - Définition détaillée des mesures et
niveaux de performance
This Technical Report was approved by CEN on 13 January 2020. It has been drawn up by the Technical Committee
CEN/CLC/JTC 5.
CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,
Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,
Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2020 CEN/CENELEC All rights of exploitation in any form and by any means Ref. No. CEN/TR 17448:2020 E
reserved worldwide for CEN national Members and for
CENELEC Members.
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 List of acronyms . 4
5 Review of EN 16803-1 Performance Metrics . 5
5.1 Potential Improvements of unstable definitions . 5
5.2 Completion With Additional Metrics . 13
5.3 Justification of the choice of percentiles . 16
6 GBPT Performance Classification . 22
6.1 General . 22
6.2 Classification logic . 24
6.3 Identification of Performance Classes . 26
6.4 Indicative Performance Figures For Main Categories Of Road Applications . 31
7 Conclusions and Recommendations . 31
7.1 Purpose . 31
7.2 Improvements of Existing Definitions . 31
7.3 Removal of Existing Definitions . 33
7.4 Inclusion of New Definitions . 33
7.5 Choice of Percentiles . 33
7.6 Performance Classification Logic . 33
7.7 Performance Classes . 34
Annex A (normative) Performance metrics as per EN 16803-1 . 36
Bibliography. 41
European foreword
This document (CEN/TR 17448:2020) has been prepared by Technical Committee CEN/JTC 5 “Space”,
the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
1 Scope
This document constitutes the main deliverable from WP1.1 of the GP-START project. It is devoted to a
thorough review of the metrics defined in EN 16803-1 and proposes a performance classification for
GNSS-based positioning terminals within designed for road applications. It will serve as one of the inputs
to the elaboration of prEN 16803-2:2019 and prEN 16803-3:2019.
This document should serve as a starting point for discussion within CEN/CENELEC/JTC 5/WG1 on a
consolidated set of performance metrics and associated classification logic. The proposals and
conclusions appearing in this document are therefore only preliminary.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 16803-1:2016, Space - Use of GNSS-based positioning for road Intelligent Transport Systems (ITS) -
Part 1: Definitions and system engineering procedures for the establishment and assessment of
performances
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16803-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 List of acronyms
ADAS Advanced Driver Assistance Systems
CAN Controller Area Network
CDF Cumulative Distribution Function
CEN Comité Européen de Normalization — (European Committee for Standardization)
CENELEC Comité Européen de Normalization Électrotechnique — (European Committee for
Electrotechnical Standardization)
ECEF Earth Centred Earth Fixed
ETSI European Telecommunications Standards Institute
GBPT GNSS-Based Positioning Terminal
GNSS Global Navigation Satellite Systems
HPA Horizontal Position Error
HPL Horizontal Protection Level
IMU Inertial Measurement Unit
ITS Intelligent Transport Systems
KOM Kick-Off Meeting
MEMS Micro Electro-Mechanical Systems
NMEA National Marine Electronics Association
PPP Precise Point Positioning
RTCA Radio Technical Commission for Aeronautics
RTK Real Time Kinematics
SPP Standard Point Positioning
TTFF Time To First Fix
5 Review of EN 16803-1 Performance Metrics
5.1 Potential Improvements of unstable definitions
5.1.1 Position accuracy metrics
5.1.1.1 Vectors vs their Norms
One thing that draws immediate attention when reviewing the metrics is some degree of ambiguity in
some of the definitions. For instance, the first Accuracy metric (EN 16803-1:2016, Table 1) refers to the
“3D position error”, which has not been explicitly defined anywhere along the document:
3D Position Accuracy is defined as the set of three statistical values given by the 50th, 75th and 95th
percentiles of the cumulative distribution of 3D position errors.
There is some discussion in EN 16803-1:2016, 3.2.1 regarding vector and scalar quantities, but no
explicit definition of the 3D position error is proposed. The position error (without the “3D” adjective)
is defined in EN 16803-1:2016, 4.3 as follows:
Position error: is the difference between the true position and the position provided by the positioning
terminal. It shall be understood as a vector expressed in some convenient local reference frame (e.g. local
horizontal frame).
This definition explicitly states that the position error shall be understood as a vector quantity. Then,
the use of the expression “3D position error” in the definition of the metric seems to emphasize the
vector character of the position error, which may be misleading since the metric actually refers to the
norm of the position error vector, which is actually a scalar quantity.
The same concern can be raised about the horizontal position error. It is therefore recommended to
include explanations on the meaning of expressions such as “3D position error” and “horizontal position
error”, making it clear that they refer to norms of vectors rather than vectors. Note that footnote 5 on
EN 16803-1:2016, A.2.1 of the document contains such a clarification for the case of the horizontal
position error, but a footnote in an annex may not be the best place for it (besides, the expression “it is
recalled” seems to indicate that the definition was written in some other, more prominent place within
the document and later removed).
NOTE The norm of a vector is not uniquely defined. To overcome this problem, it could be further specified
that the norm of interest is the Euclidean norm (square root of the sum of squared coordinates) of the vector when
expressed in a linear (and orthonormal) coordinate system. Suppose, for instance, that the position is expressed
in geodetic coordinates (latitude, longitude and height) and the position error is expressed as a latitude error, a
longitude error and a height error. The square root of the sum of the squares of these 3 quantities has no physical
meaning, and is not what is meant in the above proposed definition. It could be worth making this sort of
considerations in the standard.
A related remark (although not concerned with performance metrics) is on the identification of the
GBPT outputs made in EN 16803-1:2016, 4.2, which may require some review and perhaps include
attitude parameters (e.g. heading) or make some additional considerations on the reference frame used
to represent position and velocity (e.g. horizontal velocity could be represented in polar coordinates as
a pair consisting of speed and heading).
5.1.1.2 Along Track and Cross Track Components
Another potential issue that has been detected is the fact that the expressions “along track” and “cross
track” are undefined, yielding the definitions of “along track” and “cross track” position accuracy a little
ambiguous. It is recommended to include the definitions of these terms somewhere in the document,
especially considering that there is no general agreement as to their meanings. Note that these terms
have their roots in aeronautics and astronautics, and have been widely use to describe the motion of
space vehicles, such as artificial satellites, especially when in orbit around the Earth. Each satellite is
assigned a body-centred orthogonal reference frame with axes pointing:
— in the satellite’s direction of motion;
— in the direction orthogonal to the orbital plane;
— in the direction orthogonal to the previous 2.
However, since most orbits are nearly circular, the third direction is roughly pointing to the centre of
the Earth, and in some cases, this is how the third axis is defined, implying a slight misalignment of the
first with respect to the satellite’s direction of motion. Besides, the direction of motion is not well defined
unless the satellite’s trajectory is referred to an external (not body-centred) reference frame, such as
one with origin at the centre of the Earth. Depending on how this external frame is chosen (e.g. an inertial
frame vs one which rotates with the Earth), the satellite’s direction of motion may be different.
In road applications the situation is also somewhat complicated. It may seem natural to define the along
track direction as the one parallel to the vehicle’s velocity vector, but caution shall be taken as to the
reference frame used to define the vehicle’s motion. A natural choice would be an Earth-centred, Earth-
fixed (ECEF) frame, such as WGS84. Of course, when the vehicle is standing still, the along track direction
is not well defined using the velocity vector (which in this case is the null vector), but still the last along
track direction computed before the vehicle stopped could be used (besides, there is no actual “track”
when the vehicle is not moving, so the along track and cross track errors may not make much sense
...
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