During four years of operation, considerable practical experience has been 
gained which is a sufficient base for evaluation of the accuracy and economy of 
this method. 
The basic Shoran equipment consists of a pulse generator, a transmitter, a 
receiver installed in the airplane and a receiver coupled to a transmitter at each 
ground station. The airborne shoran set measures very accurately the time 
elapsed between the moment in which a pulse is transmitted to the ground 
station and the moment in which the return pulse is received. The distances 
read from the Shoran dials have to be corrected and reduced to geodetic 
distances. 
The primary geodetic net is established by Shoran trilatération. Distances in 
order of 200 miles can be measured with a relative accuracy of 1: 60.000. First 
experiments with Hiran indicate a relative accuracy as high as 1: 113.000. 
Horizontal control for photogrammetric mapping is established by using 
Shoran controlled aerial photography together with aero triangulation techniques. 
Each stereomodel is scaled independently to the Shoran position of the cor 
responding nadir points and pass points are determined in the same way as in 
aerial triangulation. Because of accidental errors involved in Shoran observa 
tions, the plotted positions of the pass points will differ between models and 
between lines. Using these differences, it is possible to adjust the Shoran posi 
tions of the nadir points. The adjustment can be done graphically or analytically 
using the least square method. The author feels that by using this method it 
should be possible to determine positions with a probable error of ± 6.5 m. 
A direct use of Shoran controlled photography for horizontal bridging was 
suggested by the Army Survey Establishment and is being carried out by Cana 
dian Aero Service and Spartan Air Services. Shoran controlled photography is 
flown at an altitude of 20.000 ft. (giving a range of approximately 200 miles) 
every one degree of longitude and every 20 minutes of latitude. As a result, large 
areas are covered by relatively dense grids of Shoran points which are used to 
control aerial photography at a scale of 1/62.000. 
Since 1952 Canadian Aero Service and Spartan Air Services have established 
horizontal control by Shoran controlled aerial photography for an area of 
500 000 square miles. The probable error in the position of nadir points using 
this method is ± 13.5 meters. It could be possible to improve this accuracy 20 % 
to 30 % by photogrammetric methods described in this paper. 
Shoran Electronic survey methods provide a very important aid in photo 
grammetric mapping. Particularly in mapping of inaccessible, large areas, Shoran 
has proved itself as the only economical and fast method of providing primary 
and secondary horizontal ground control. 
Application de shoran pour contrôle horizontal en photogrammétrie aérienne 
L’influence de la science électronique sur la photogrammétrie est considérable. Les instruments 
électroniques permettent aux ingénieurs de photogrammétrie d’établir la position du point nadir 
de chaque photographie aérienne individuelle au moment de la pose, ainsi que d’indiquer l’élévation 
correspondante du terrain. 
Shoran et Hiran, la version modifiée, indiquent la position, tandis que l’altimètre radar mesure 
le profil du terrain. Ces informations indépendantes additionnelles sont d’une grande valeur aux 
aérotriangulations en terrains inaccessibles. 
Au Canada, Shoran est appliqué non pas seulement par le Service Géodésique du Canada pour 
l’établissement d’un réseau primaire de points géodésiques, mais il est également adopté par des 
compagnies photogrammétriques privées, telles que Canadian Aero Service et Spartan Air Services 
pour le contrôle horizontal nécessaire à la compilation des cartes photogrammétriques des territoires 
nord du Canada. 
L’instrument Shoran qui se trouve dans l’avion mesure avec grande précision le temps qui s’écoule 
entre le moment dans lequel un pouls est transmis à la station Shoran terrestre, et le moment où 
le pouls, re-transmis par la station terrestre, est reçu dans l’avion. Ce temps mesuré est transcrit 
automatiquement en milles.