wa 3 Minuten ho- 
Horizontangaben 
we have a discus- 
a very brief com- 
s paper which is a 
catalogue of the 
ible to the aircraft 
planning any sur- 
ously be guided by 
onsiderations, and 
? to equip an air- 
| systems listed in 
viously impossible. 
of areas devoid of 
sert or a thick for- 
tage if the naviga- 
pletely contained 
pect, a Doppler is 
ble advantage but 
ted out, the defect 
nuth. However, in 
high accuracy, but 
is one of the forms 
tions, the azimuth 
i| survey purposes 
an inertial naviga- 
ness. I would very 
your notice a new 
pment which may 
lis respect, prima- 
tography in desert 
he necessity of in- 
ations. There is al- 
mercial aircraft a 
ard-looking radar 
cloud and collision 
the antenna it can 
vice for picking up 
1g detail. The de- 
; the practical pro- 
1s a reflecting sur- 
e to show you this 
or which has these 
ich sphere has a 
our square metres. 
h the diameter and 
er would have a re- 
) square metres. A 
uld produce a very 
il type of forward- 
ballasted so that it 
right direction it 
a number of these 
SURVEY NAVIGATION, DISCUSSION 97 
_ to form points of reference for subsequent 
return to the same area. 
] have mentioned this now: the development 
came after 1 had time to communicate with Mr 
Corten, but is seems to me that it is a possible 
development which would assist in maintaining 
the survey equipment solely in the aircraft. 
Mr F. L. CORTEN: Thank you very much, 
Mr Attwell. 
First of all, I want to pay tribute to the 
cooperators on this panel who supplied me with 
a lot of data necessary for the compilation of 
this paper. We came to the conclusion in a few 
words that many methods are available, and 
there are probably more available than I thought 
when I was making my report. I am just playing 
now with the thought brought up by Mr Attwell, 
combining this with the navigational methods 
developed by Mr Gleize and Mr Carnec at 
I G N. Such an combination would be extremely 
useful, particularly for the heading which is a 
very big point. There are in this field two sa- 
lient points: one is that good navigation is now 
possible by means of visual contact if you have 
a good crew, and by means of complete instru- 
ment navigation. Also, it seems to me that ver- 
ticality can be obtained with a high degree of 
accuracy by simple means, a horizon camera, 
for instance, and with the inertial vertical. So 
I may say that in both ways — with the conser- 
vative method and with the completely auto- 
matic method — accurate data can be obtained, 
so there is hardly any justification for not using 
them if they can economise aerial survey. The 
only problem now will be to ask how to apply 
it in photogrammetry, and this I think is a prob- 
lem which must be faced by Commission I in 
the next period of working.