altitude, the atmospheric refraction and the topography. It is considered that horizon picture 
tilts can be compared with tilt values obtained from relative orientation in strip triangulation 
under proper weighting of these values to determine the potential of such auxiliary data for the 
performance of aerial triangulation. Reference is made to : " Noggrannhetsundersôkning avHo- 
rizontkameran Wild HC 1 ", by Pentti Kaasila, Institute of Photogrammetry, KTH, Stockholm 
70. [6]). 
Switzerland : 
Due to a dense network of existing ground control in this country there is no immediate 
application of aerial triangulation with auxiliary data. Experiments are being performed in con 
nection with the Wild Company using auxiliary data provided by the Wild Statoscope and the ho 
rizon camera Wild HC 1. For the measuring of the horizon pictures the stereomicroscope is 
used ; however, also experiments with a microfilm read out instruments are presently in pro - 
cess. Since these tests are not yet completed no further information can be given at this time. 
For the future the design and use of gyrostabilized camera mounts are considered. 
The Netherlands : 
Due to a very dense network of available ground control in this country it is felt that 
there is no need for the performance of aerial triangulation with auxiliary data. Nevertheless 
it is expected that in the future some use will be made of statoscope and A. P. R. - data. Fur - 
thermore, it is assumed that the subject : Aerial triangulation with auxiliary data, is also stu 
died in the I. T.C. ; however, no particular information has been obtained from this institution. 
U. S. A. 
Headquarters Aeronautical Chart and Information Center, U. S. Air Force. 
This agency has a continuing interest in the development and use of aerial triangulation 
with auxiliary data but it is felt that no specific information can be made available at this time. 
Corps of Engineers, U. S. Army, Army Map Service. 
This agency uses electronic (Shoran) controlled photography to provide auxiliary data 
for the establishment of horizontal photogrammetric control used for : 1 : 250, 000 scale map 
ping. It is pointed out that this method has proved to be an economical mean of obtaining hori 
zontal control over vast areas in a relatively short period of time where ground control is vir 
tually nonexistent. - It is planned to use in the future more precise electronic horizontal con 
trolled photography (Hiran and Shiran) and to obtain electronic vertical controlled photography 
by APR which could be related to the electronic horizontal controlled photography. - To obtain 
new horizontal ground control the instrument Shoran nadir coordinates x and y are determined 
at the Wild Autograph or the Zeiss Steroplanigraph which requires additional instrument rea - 
dings and computations performed on the electronic computer Honeywell - 800. Individual strip 
triangulations (40 to 70 models, flown from 20, 000 to 30, 000 ft above ground with a 6 " wide 
angle camera) are adjusted on the basis of the nadir coordinates using a least squares adjust 
ment programmed at the Honeywell - 800 which transforms the aerial triangulation points to 
UTM coordinates using the given UTM coordinates of the Shoran control stations. - Ground con 
trol for the adjustment of Shoran controlled aerial triangulation (strip triangulation) are located 
on or tied to existing I. and II. order triangulation stations or are established by airborne elec 
tronic trilatération with controlling stations approximately 200 miles apart. - The accuracy of 
such aerial triangulation was found sufficient for 1 : 250, 000 scale mapping requirements. - In 
average two man hours instrument time is required per model, and one man hour per model for 
the adjustment utilizing the electronic computer. 
Coast and Geodetic Survey 
In this agency triangulation with auxiliary data in general is not used. It is felt that 
through free aero-triangulation with conformal adjustment greater accuracy can be obtained, 
and this even for single strips, than with aerial triangulation with auxiliary data. - Currently 
the use of solar directions obtained with a solar camera is evaluated. This camera designed by 
the U. S. Army Ballistics Research Laboratory consists of two Wild RC-7 plate camera cones 
- 28 -