MEASUREMENT IN HAZARDOUS ENVIRONMENT : REVIEW OF SEVERAL APPLICATIONS
Arnaud DUMONT - Technical Manager
ESIC France - Working Group WG V/3 - Structural and Industrial Measurements with Consideration of CAD/CAM aspects
KEY WORDS : Measurement, Underwater, CCD, Sensor, Digital, Photogrammetry.
ABSTRACT
How can we carry on three-dimensional measurements where the level of radioactivity is high ? and underwater ? and into
a thermal chamber ?
Such questions have recently found an impressive answer, mainly through the technique of digital photogrammetry.
In this paper, we will discuss about applications done in each of the items mentioned above. The accent will be put on the
industrialization of the process and on the CAD/CAM aspects.
RESUME
Comment réaliser des mesures tridimensionnelles lorsque le taux de radioactivité est élevé, sous l'eau ou dans une
chambre thermique ?
Une impressionnante réponse a récemment été apportée à ces interrogations et notamment par le biais de la technique de la
photogrammétrie digitale.
Ce document se propose de présenter les différentes applications réalisées dans chacun des cas de figure cités ci-dessus.
L'accent sera notamment mis sur l'industrialisation du procédé et sur les aspects concernant la CAO/DAO.
1. THE ORIGIN
First of all we have to define what we call hazardous
environment and what kind of measurement we need to
carry on.
An easy way to imagine what we call an hazardous
environment is to say that its a place where noone
should go ! In practice, someone, in some of them, could
go but not for a long time or with big difficulties.
This definition clearly concerns :
e nuclear environment,
underwater,
thermal chambers,
vacuum chambers,
pit for pressure test,
etc...
But what kind of measurement is required in such
areas ?
We have to distinguish two purposes : the first one is for
maintenance ; for example when an equipment has to be
changed or when an incident occurs. One of the
traditional methods consists in building a jig even with
the possibility of mechanical measurements. This costs
a lot, is not very fast and not accurate at all. It’s mainly
the case of nuclear and underwater environments.
The second purpose is for testing ; for example, when an
equipment has to be tested under thermal or vacuum
conditions or when the dimensional information has to
be related to a pressure value. We are speaking for
example of thermal or vacuum chambers or pits for
pressure tests.
Hazardous environment, maintenance or test purposes,
needs of dimensional information ; the scenery is ready :
let the actors in (we should say out !).
Basically, the idea is to use a CCD sensor which allows
mainly two things :
e to penetrate an hazardous environment (with or
without protection),
e to check the data in real time and to have the results
quickly.
Therefore, the use of a CCD sensor determines the study
of the following aspects :
e first is what could be called the «hard» and will
mainly concern the sensor, its canister and the
separating glass,
e second is the «methodology» for data capture,
e third is what could be called the «soft» and will
mainly concern the way to process the data.
2. THE SOLUTIONS
2.1 Solutions for hard
The development of the technique of 3D measurement
using digital photogrammetry is the main factor that
made applications easier. In fact, some successful
experiences have been carried out over the last ten years,
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
using the
big restraii
e val
eo lor
CCD sens
sufficient,
immediate
very quick
CCD sens
KODAK 1}
42 and :
resolution
improvem
Canisters
developme
the optica
results car
the isolati
cooling sy
protection
2.2 Solu
The range
leads to di
e concer
object
sensor
e concer
stereo
config
Concernir
cases (obj
and senso
our exper
fixed and
e there:
e there
geome
On the of
camera th
So each c;
accuracy
The other
between
configura
e ther
being
e thepc
The poss
considere
approach
good res
surfaces ¢
and the st
or edges «
the conve
effect of ]
