G. McNeil: Macrophoto- 
grammetry with the 
Donaldson Stereo-Camera. 
(Pubi. Y M 2; 
voir USA Y) 
La dernière communication de cette séance est celle de M. G. McNeil, Etats- 
Unis, intitulée »Macrophotogrammetry with the Donaldson Stereo-Camera». 
Résumé: 
The Donaldson Stereo-Camera is being utilized primarily in the fields of 
ophthalmology and pathology for qualitative analyses. The purpose of this 
report is to demonstrate and to determine the quantitative capabilities of a 
camera designed specifically for the interpretation of stereoscopic photographs 
of the eye and of gross specimens. 
The only Donaldson Stereo-Camera conveniently available for metrical analy 
sis was located at the Armed Forces Institute of Pathology, Washington, D. C., 
which undoubtedly is one of the most modern and well equipped laboratories 
of its kind in the world. The responsible officials of the Institute encouraged 
the metrical analysis of the Donaldson Stereo-Camera. A request was made to 
the Institute for a one day loan of the camera for the purpose of making an 
elaborate calibration. The loan was not approved for the very legitimate reason 
that the camera must remain in a continual stand-by condition for emergencies 
and other unscheduled demands. 
Inasmuch as the camera could not be removed from the Institute, it was 
decided to conduct the analysis in a more simplified manner so that technicians 
not versed in the science of photogrammetry can duplicate the procedure out 
lined in the report. 
The accuracy of the equipment together with the simplified procedure ex 
ceeded expectations. The basic principles comprising the system can be utilized, 
in many instances, for special applications within science and industry. 
Increased production and accuracy requirements can soon justify the amorti 
zation of more elaborate photogrammetric plotting equipment and the related 
refinements. 
If greater accuracy is required, it is recommended that the camera base be 
increased inasmuch as the vertical accuracy is directly proportional (approxi 
mately) to the camera base. 
The aluminum test object in this report was specifically chosen inasmuch as 
it could be easily measured by means of a micrometer for comparison with the 
photographic method. However, if a pencil attachment is secured to the stereo 
meter, then the cornea and other gross specimens can be contoured, using the 
tick marks as control. 
La macrophotogrammétrie avec l’appareil Donaldson 
L’appareil Donaldson est principalement utilisé dans l’opthalmologie et la pathologie, dans des 
buts qualitatifs. Description est faite des essais pour déterminer les capabilitiés quantitatives de 
l’appareil destiné à l’examen stéréoscopique de l’oeil humain ainsi que d’autres specimen bruts. 
Le seul appareil à portée de main étant celui de l’Institut de Pathologie des Forces Armées à 
Washington, celui-ci fut solicité en vue d’en faire l’essai. Cependant, son usage courant n’en 
permettant pas le transport à d’autres lieux, une analyse simplifiée fut conçue permettant à de 
non-photogrammètres d’exécuter les procédés nécessaires. 
La précision obtenue dépassa les attentes. Les principes du système utilisé permettent d’envisager 
un grand nombre d’applications scientifiques et industrielles de l’appareil. 
L’emploi d’un sujet-échantillon d’aluminium pour les essais est justifié par la facilité d’un 
contrôle au calibre micrométrique. 
Cependant, pour l’étude de l’oeil humain, l’emploi d’un crayon rattaché au stéréomètre est 
préconisé pour un relevé contouré. 
Le Président lève la séance.