PHOTOGRAMMETRIC PORTRAYAL OF
SURFACE TEXTURES TO AID SKID
RESISTANCE STUDIES
W B R Smith
Department of Main Roads, Australia
This paper is republished here, with minor
changes, with the kind permission of the
Australian Road Research Board.
ACKNOWLEDGEMENTS
The author is endebted to:
- Professor R B Forrest, of the Department of
Photogrammetry at the University of New
South Wales, both for his guidance and en-
couragement in the development of thoughts
and concepts associated with relevant stu-
dies and for establishing the initial con-
tact between the author and Dipl-Ing Edmund
Layton, M.I.E Aust, of C.S.I.R.O, without
whose experience, enthusiasm and interest
in micro-photogrammetric studies of the
geometry of small objects, the work on which
this paper reports would not have been
initiated;
- The Director of the National Measurement
Laboratory, of C.S.I.R.O, for permitting
Edmund Layton to contribute his talents to
these studies and for allowing the use, in
this work, of the facilities of that Labora-
tory and the expertise of other staff mem-
bers, of whom Mr D A Roze, A.I.A.P, deser-
ves special mention;
- Dr W O Yandell, of the Department of Engi-
neering Materials of the University of New
South Wales, for establishing relevance of
these scales of studies of the geometry of
surfaces to practical problems (in the con-
text of skid resistance of pavements and
aggregates) facing highway engineers;
- Mr BJ Sexton, B.E, F.I.E.Aust, F.C.I.T,
Commissioner for Main Roads, for permission
both to initiate and pursue studies in this
context and to submit this paper for presen-
tation at the Ninth A.R.R.B Conference.
ABSTRACT
Photogrammetric instruments and procedures
have developed principally to portray the
spatial geometry of topographic surfaces, in
units of the order of magnitude of metres, in
graphical or digital format. Contour plans,
101
contoured orthophotographs or digital terrain
models - derived from imagery acquired with
aerial survey cameras - are used widely for
location, design and construction purposes in
highway engineering.
For other highway engineering purposes, stu-
dies are required of the spatial geometry of
other surfaces at larger scales. Using photo-
grammetric concepts and instruments, but image
acquisition systems differing from aerial sur-
vey cameras, the form or texture of surfaces
can be portrayed - conveniently and convin-
cingly - in units of orders of magnitude of
millimetres or micrometres, or even nano-
metres.
Progress is reported in the development of
relevant image acquisition and evaluation
Systems and procedures, prompted by needs to
study spatial relationships in the context of
the skid resistance of pavements and aggre-
gates, principally relevant to portraying
pavements in millimetre magnitudes. Compar-
able progress in portraying aggregates in
micrometre magnitudes is predicted.
NEEDS FOR SURFACE TECTURE STUDIES
IN SKID RESISTANCE
Dr W O Yandell, in his paper presented to
Session 17 of the Eighth A.R.R.B Conference
in Perth (Yandell and Gopolan, 1976) and in
numerous other publications, has established
that tyre tread rubber abrasion increases as
the participating scales of texture, of the
road surfaces, increase in fineness and in-
crease in ruggedness. Dr Yandell has expres-
sed interest in obtaining series of digital
observations of the surface geometry of road
aggregates, significant to orders of magnitude
Of micrometres, in this context, in the
further pursuit of studies of the theory of
hysteretic sliding friction.
Discussions with other engineers, within the
Department of Main Roads and elsewhere, sug-
gested that there may be needs for studying
the textures of pavements at macroscopic
scales, aimed at portraying quantities of the
order of magnitude of millimetres, both graph-
ically and digitally. Amongst objectives of
such studies may be determinations of the hy-
draulic properties of road pavements, with a
view to proposing characteristics which might
inhibit tendencies for vehicles to lose con-
tact with a pavement during periods of heavy
rain precipitation, by "aquaplaning". Other
objectives may also be served by studies with-
in this range of portrayal of textures.
It thus seemed warranted to develop image ac-
quisition and evaluation systems capable of
recording observations significant respective-
ly to these orders of magnitude - micrometres
and millimetres - while the further possibi-
lity of extending to the range of nanometres
does not at this time appear to warrant the
committment of resources for highway enginee-
ring purposes now apparent. But such an ex-
tension would not seem to pose undue techno-
logical problems, if a practical application
were to become evident.
PROBLEMS OF PORTRAYING SURFACE TEXTURE
Contact Metrology Inappropriate
In studying the microscopic textures of aggre-
