Bsi bs au 228 2 1989 (2000) iso 8721 1987

BRITISH STANDARD AUTOMOBILE SERIES

BS AU 228-2:
1 989
ISO 8721 :1 987

Impact tests on road
vehicles —
Part 2: Specification for measurement
techniques using optical
instrumentation
[ISO title: Road vehicles — Measurement techniques in impact
tests — Optical instrumentation]

UD C 62 9 . 1 1 : 62 0 . 1 /. 1 1 1 . 1


BS AU 228-2:1 989

Committees responsible for this
British Standard

The preparation of this British Standard was entrusted by the Automobile
Standards Committee (AUE/- ) to Technical Committee AUE/7 upon which the
following bodies were represented:
Association for Consumer Research
Automobile Association
Child Accident Prevention Trust
Consumer Policy Committee of BSI
Department of Transport (Highways)
Department of Transport (Transport and Road Research Laboratory)

Institute for Consumer Ergonomics Ltd.
Man- made Fibres Producers’ Committee
Medical Research Council
Ministry of Defence
Motor Industry Research Association
National Automobile Safety Belt Association
Royal Automobile Club
Royal Society for the Prevention of Accidents
Society of Motor Manufacturers and Traders Ltd.
University of Birmingham

This British Standard, having
been prepared under the
direction of the Automobile
Standards Committee, was
published under the authority
of the Board of BSI and
comes into effect on
31 March 1 989
© BSI 01 - 2000

The following BSI references
relate to the work on this
standard:
Committee reference AUE/7
Draft for comment 86/77884 DC

ISBN 0 5 80 1 685 9 X

Amendments issued since publication

Amd. No.

Date of issue

Comments


BS AU 228-2:1 989

Contents

Page
Committees responsib le
National foreword

ii

1

Scope and field of application

1

2

Reference

1

3

D efinitions

1

4

Performance

1

Annex D istortion index measurement methods

2

Figure — Target for distortion index determination

3

Pub lications referred to

© BSI 01 - 2 000

Inside front cover

Inside back cover

i

BS AU 228-2:1 989

National foreword

This Part of BS AU 228 has been prepared under the direction of the Automobile
Standards Committee and is identical with ISO 8721 : 1 987 “Road

vehicles —
Measurement techniques in impact tests — Optical instrumentation”, published
by the International Organization for Standardization (ISO).
Terminology and conventions. The text of the International Standard has

been approved as suitable for publication as a British Standard without
deviation. Some terminology and certain conventions are not identical with those
used in British Standards; attention is drawn especially to the following.
The comma has been used as a decimal marker. In British Standards it is current
practice to use a full point on the baseline as the decimal marker.
Wherever the words “International Standard” appear, referring to this standard,
they should be read as “Part of BS AU 228”.
Cross-reference
International Standard

C orresponding British Standard

ISO 6487: 1 987

BS AU 228

Impact tests on road vehicles

Specification for measurement techniques
and general instrumentation

Part 1 : 1 988
(Identical)

A British Standard does not purport to include all the necessary provisions of a
contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity
from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pages i and ii,
pages 1 to 4, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had
amendments incorporated. This will be indicated in the amendment table on the
inside front cover.

ii

© BSI 01 - 2000


BS AU 228-2:1 989

1 Scope and field of application

This International Standard defines performance
criteria for an optical data channel used in impact

tests on road vehicles, when numerical time and
space data are taken from the images to analyse
impact test results.
The requirements are to facilitate comparison
between results obtained by different laboratories.
The annex gives a method of measuring the
distortion index as a quality parameter of the
optical data channel using a standard target, and,
as an alternative, an indirect method.
This International Standard complements ISO 6487
which covers non-optical instrumentation used in
impact tests on road vehicles.
2 Reference

ISO 6487,

Ro ad vehicles — Techniq ues o f

m easurem ent in im p act tes ts — Instrum entatio n.

3.6
imaging rate

frequency of renewal of information for a given point
expressed in renewals per second or in images per
second when all the points of the image are renewed
simultaneously
4 Performance

The performance of the optical data channel shall be

evaluated initially to establish performance levels;
this evaluation shall be repeated whenever the
system is modified to an extent which could cause a
change in accuracy.
4.1 Distortion index

The distortion index shall be assessed using the
photographic target and procedure described
respectively in A.1 .1 and A.1 .2 of the Annex. It shall
be evaluated as indicated in A.1 .3 . The distortion
index shall not exceed 1 %.
4.2 Time base

A time base is required. It shall permit
For the purposes of this International Standard, the determination of the time between recorded events
to an accuracy of the reciprocal of the imaging rate
following definitions apply.
or 1 % of the actual time, whichever is greater.
3.1
3 Definitions

optical data channel

1)

system composed of an image-taking device
(e.g. a camera), a recording medium for these
images (film, disc, magnetic tape, etc.) and a system
for analysing the images, including any analysis
procedure and data correction that modify the

content of the data
3.2
distortion index

quality parameter of the optical data channel
3.3
analysis system

system to measure and collect the coordinates of
target points as a function of time

3.4
time-base system

device allowing determination of the time interval
elapsing between any two recorded events
3.5
time origin identification device

device to identify the instant chosen as the time
origin, usually the beginning of the impact

4.3 Time origin identification device

The accuracy of the device shall be equal to the
reciprocal of the imaging rate.
4.4 Imaging rate

The imaging rate shall be left to the user’s
discretion, taking account of all factors including:

— the goal to be attained;
— the limitations due to the equipment
(e.g. blur);
— the need to combine data from several
image-taking devices and from electronic
recordings of the impact test.
The user’s choice shall be guided by the distance the
recorded point moves between two images analysed.
This distance shall not exceed any accuracy
requirement there may be on determination of
position.
4.5 Reference length

A length calibration shall be carried out which
permits determination of lengths within any
requirements there may be on accuracy.
In the absence of such requirements, it is
recommended that determinations of length to
within ± 1 % of the diagonal of the picture should be
possible.

1) The influence of the operator on accuracy has not been taken into account during the development of this International

Standard.

© BSI 01-2000

1

BS AU 228-2:1 989

Annex Distortion index measurement
methods
(This annex forms an integral part of the Standard. )

The diameter,

d

, and the standard deviation,

respectively shall be calculated taking
the 40 diameter values
following equations:

di

s

,

into account from the

A.1 Standard target method
A.1 .1

Test target

A rectangular target of type and dimensions in

conformity with the figure shall be used.
where

This target shall be divided into four parts by

N

= 40

j oining the centre points of the two opposite sides. In
each quadrant thus obtained, and at the target
centre, circles 400

± 1 mm in diameter shall be

drawn.
The five circles shall be marked on their

N

circumferences with 1 6 reference marks, this

where

defining eight diameters for each, and

The distortion index is equal to the ratio of the

hence 40 diameters for the whole target.

standard deviation,

A.1 .2

Test method

s
d

– 1 = 39

s

, to the mean diameter,

d

, i. e.

---

The target shall be recorded full- frame by the
image- taking device which forms one element of the
optical data channel to be tested.

A.2 Alternative (indirect) method

The image- recording medium to be used for

Other targets with different sizes or patterns of

calibration shall be of the same type and quality as

reference marks may be used, in which case the user

those used for impact testing. It shall be analysed

shall determine the distortion index indirectly.

using the analysis system.
The coordinates of the marks of each diameter

di

shall be measured on the same frame while the

coordinates of the marks of different diameters shall
be measured on consecutive analysed images.

A.1 .3

Calculation of results

The 40 diameters

di
y y

There is then also a need to show that the indirect
method gives results equivalent to those using the

target specified in A.1 .1 .
This may be of advantage when for instance a target
with a rectangular pattern of reference marks is
used for the determination of lens corrections, which
are needed in case of some wide- angle lenses.

shall be calculated between two

points, P and Q, from the equation

di

2

= [(

x x
P

–

Q)

2

+ (

P

–

Q)

2 0, 5

]

© BSI 01 - 2000


BS AU 228-2:1 989

Figure — Target for distortion index determination

© BSI 01 - 2 000

3


4

blank


BS AU 228-2:1 989

Publications referred to

See national foreword.

© BSI 01 - 2 000


BS AU 228-2:
1 989
ISO 8721 :1 987

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