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If there are tie points at the beginning and at the end of the profile th 
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reveal only accidental errors. It proves indirectly that great reliability : ys, 
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the use of the isobaric surface as the reference surface and also 0 be Nag, 
n the alga; — 
surements on the flight. S alimetion, 
The ground profile and the ground clearance curve are recorded o 
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tape. Positioning photographs are taken coincident with the Survey SA yon 
photograpk, i 
irs : Optical gyi 
positioning camera and the electromagnetic beam must be known and reg XIS of 
At the moments of exposure of the positioning camera speci 
intermediate preset intervals. Relative orientation between the 
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al marks are mad 
graphs. Thus, points located on the ground through the medium of positioni 
also located on the diagram. 
As to the use of infrared oblique photographs, the experimental work wa 
Vas shy 
= 
isobaric Surface 
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path of aircroft 
  
  
Fig. 1. 
about three years ago. The photopgraphs are made not as is usual, but fore or aft de 
the flight line. Depending upon atmospheric conditions and type of terrain it is suffi 
if an infrared oblique photograph is made for every 3rd to 5th vertical photogr! 
straight line is then extended throughout the strip of oblique photographs. Comes 
applied for the elevation differences of the straight line points, earth curvature, dis 
of the photogrammetric objectives and atmospheric refraction, determine the real %; 
of the constructed line on the earth surface. The first experiments carried out in ji 
hilly terrain over distances up to 240 kilometres revealed a mean square deviatnis 
the straight line of = 9 m. | 
After the general high accuracy of the radar profile and the infrared phi 
  
  
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technique were established, the proper time arrived to include these techniques i # 
procedure of aerial tiiangulation. q 
Using APR data, a simple and logical basis for height adjustment in the bi 
strip was first of all obtained. In addition, the introduction into the instrumental i 
of altimeter readings (statoscope data) and ground clearances, controls not oly 8 
cumulation of z-errors but also of errors in scale, while the possibility of further aja 
is still open. Thinking in terms of a polar coordinate system, the determination #* 
elevations of the bridged points and their distances from the origin is based 01 ii 
APR data. It remains only difficult to control the direction of the strip or its transit 
eurvature. For this purpose, the infrared oblique photographs are used. 
    
  
  
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