efore, if after put-
s in relative orien-
e according to the
by the statoscope,
he fore and aft di-
ral direction by in-
strips, you can le-
direction also. Of
ou heights on the
u must come down
the ground in or-
you want to know
rder to know how
| can get from the
yr clearance. How-
rather overlooked
APR is that it is
1 in order to level
| you can level the
a statoscope. That
hink on the A P R,
then is concerned
down the strip you
ou must know the
1uch to come down
al to the ground.
onal measurements
rance of the radar
e error from accu-
quire it necessarily
ph. Therefore, you
n this level.
idition to what has
\ PR, I would like
field of application
he reduction of the
) reduce the obser-
e and we must in-
'equire knowledge
e used in a simple
s in the drift angle.
y know that in Ca-
nited investigations
in view of its direct
and we found that
with quite high de-
ed figures of about
‚So it is quite good.
> Doppler system is
which accumulates
1e longer distances
e. We find, for in-
ces of the order of
'rrors in distances
es. Comparing with
can be used for the
SURVEY NAVIGATION, DISCUSSION 95
same purpose, the APR seems to be at least
ten times more precise. Therefore, you can see
there are very nice applications for both me-
thods, but for the direct mapping operation we
think that the A P R probably is superior, even
as far as the determination of distance is con-
cerned, and also A P R can set the determina-
tion of elevation.
I do not think we have time — and this is not
the appropriate Commission — to discuss the
direct application of A P R for mapping, but I
would not entirely be in agreement with Mr
Eden.
Herr Dr BRUCKLACHER: Ich möchte etwas
bemerken noch zum Problem Statoskop oder
Radarprofilhóhenmesser. Der Statoskop gibt
Hóhendifferenzen für einen ganz genau defi-
nierten Punkt, nàmlich für den Aufnahmestand-
punkt. Diese Hóhendifferenzen kónnen infol-
gedessen sehr einfach und auch sehr eindeutig in
einem Auswertegerät bei der Aerotriangulation
eingesetzt werden. Sie verhindern dann die be-
kannte Aufbiegung der Streifen. Beim Profil-
hôhenmesser dagegen hat man ein Profil am
Boden. Man kann dieses Profil natürlich für
die Massaberechnung mitverwenden, wenn man
aber an die Hôhenbestimmung denkt, so wird
man eben dieses Profil verwenden, um nachher
bei der Ausgleichung eine Vermittlung der
Fehler zu erhalten. Die einzelnen Punkte im
Profil sind aber nicht so präzise bestimmt, ein-
mal wegen des Abstrahlwinkels des Radarpro-
filgerätes, zweitens wegen der Topographie im
Gelände, längs dem Profil, und schiesslich we-
gen der Identifizierung der Profilpunkte im
Messbild selbst auf Grund von Bildneigungen,
die auch immer etwas beeinflusst. Insofern
kann man im Hinblick auf die Aerotriangula-
tion die Frage stellen, ob der Radarprofilmesser
oder das Statoskop mehr Vorteile bietet. Der
Radarprofilmesser hat mindestens einen we-
sentlich grösseren Umfang in Bezug auf den
Einbau im Gerät und auch wahrscheinlich in
Bezug auf die Kosten.
Mr F. L. ConrEN: Mr Sewell is not here
otherwise I would have been inclined to ask him
about the performances of Aerodist. This is a
system which, as you may know, is developed
from the Tellurometer — it is being developed
now — and is being tried now in the US A in
flight trials. I was very interested in the first
practical flight test results, but I fear that we
must wait for another occasion.
Therefore, switching over now to the prob-
lem of verticality I would like to remind you
of Mr Trombetti's publication about solar peris-
copes in Commission III. We will not repeat it
here because that is more the application, but
we came to the conclusion that in analytical
triangulation the solar periscope can be even
more accurate than it is now.
Mr Trott from Aeroflex has some interest-
ing things to tell us.
Mr. T. TROTT: There are essentially two
classes of vertical reference systems for airborne
applications. The first class uses a pendulum
for its basic reference. A gyroscope is slaved to
this reference and the slaving is made so weak
that is does not respond to the short-period de-
viations of the pendulum. Various systems in
this class involve using various levels of approx-
imate corrections to the pendulum, but pre-
cision is always dependent on the presumption
that the mean position of the pendulum is true
vertical. This approaches the truth only for no-
minally straight and level unaccelerated flight.
The second class of systems are the inertial
systems. This type of system is a Schuler system,
designed to give optimum verticality and low
motion rates such as are required in photogra-
phic platforms. The basic principle of operation
is to establish a stationary platform, stationary
relative to the inertial base, relative to the fixed
stars in other words, by using three gyroscopes
which are mutually perpendicular. Two acce-
lerometers are located in the platforms and these
are used to measure the linear accelerations of
the vehicle as it moves over the earth’s surface.
The integration of these measurements of acce-
leration is then used to rotate the platform in
inertial space so that it always keeps up with
the position of the local vertical.
Systems of this sort are almost entirely de-
pendent for their accuracy upon the accuracy of
the components involved. It can be shown that
a perfect system of this type is entirely analo-
gous to a pendulum equal in length to the
earth’s radius which would oscillate at a period
of 84 minutes. Such a pendulum, and the system
based on this principle, would be capable of a
high degree of accuracy without any limitation
or restrictions on the flight conditions, except
those limitations imposed by the instrumenta-
tion. In the case of the Aeroflex vertical refer-
ence system built on these principles, the only
limitations are restrictions to less than five g's
of acceleration, less than 900 knots speed, since
the integration of the acceleration is limited, and
no greater than + 85° in pitch. As long as the
aircraft navigation and manoeuvres remain
within these limits the system will produce a
