International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
where AH;= height difference from each node (Hp) to the 
reference plane. The reference plane height (Hg) is 
taken as the lowest DTEM height. Then AH; = Hp; - Hg 
Zr = relative height flight, determined as the difference 
between height centre projection Zo y Hr. 
B = photographic base of the stereoimagen (B=Zp/5 
guarantee an adequate stereoscopic vision) 
The coordinates X of each DTEM node in the stereomate system 
is determined by the Eq. 6: 
Xi=X; tPy (6) 
where — X'; : coordinate in the X" axis of the node j in the 
stereomate system 
X; : coordinate in the X axis if the node j in the terrain 
system 
Px; : horizontal parallax ofthe node j 
2.8 Transformation of the DTEM subcells to the estereomate. 
The position of the DTEM nodes in the terrain system and in the 
stereomate system allows to determine the parameters of 
projective transformation between both systems. From them, the 
position of cach DETM subcell is determined in the stereomate, 
generating an array with the same number of subcells but of 
different sizes and forms (Figure 5). Obviously, each deformed 
subcell has associated the grey tone corresponding pixel in the 
orthophoto. 
DTEM cell = 
Orthophoto cell 
DTEM cell + paralax = 
Stereomate cell 
Cell Deformed cell 
   
Regular 
subcells 
Deformed 
subcells 
Een aan 
Figure 5. Correspondence between DTEM and stereomate. 
  
2.9 Determination of the grey levels of the stereomate color 
bands 
The stereomate imagen is created from the digital orthophoto 
radiometric values. There is a geometric variation between the 
orthophoto and the stereomate number of pixels, due to a 
deformation of the stereomate subcell width. Therefore, to 
generate the stereomate image, it is necessary to have an array of 
pixels to the same resolution as those of the ortofoto. It happens 
then, that in a row of the stereomate the number of pixels is 
different than in its corresponding row in the ortofoto, see figure 
6. Then, a correspondence is established between the stereomate 
cells and the stereomate image pixels, in order to assign the 
respective tone. 
Stereomate cells 
  
Stereomate 
[let 
  
  
Figure. 6. Linear interpolation of the stereomate pixels 
2. APPLICATION 
The procedure was used on the ancient town of San Antonio of 
Mucuiio, located in the State Merida, Venezuela, of mountainous 
relief. The SFAP are selected by two reasons: i) a budget reduced 
to realize the survey of the zone, disabling the photogrammetric 
survey in standard format, and ii) a topographic survey of the 
area, made six years behind, allowed to compare it with the 
survey obtained through aerial photography using SFAP. 
From the beginning, it was considered to take the photographs, 
having the control points previously marked on the area. Nineteen 
ground control points were measured, which were used as control 
points for the restitution of the aerial photographs. These points 
were signalised on the ground with two white concentric circles 
before the flight. The result is that the points appear as white 
circles clearly defined in the photography. 
It was used an Hasseblad 553 camera (format 70 mm) with an lens 
of f = 40 mm, mounted in a special support coupled to the 
baggage porthole of a Cessna 182 plane. Over the area were 
realized three flight passes, with heights between 8000 and 10000 
feet above the sea level. 
  
  
  
  
  
Figure 7. DTEM perspective view of application area 
    
Interna 
Tenn 
The ph 
heights 
generati 
from the 
m (Figu 
scanned 
The res 
the para 
and colt 
in milli 
paramet 
Table 1 
photogr 
Contro 
points 
  
t2 
UJ 
  
a97 148 
b, 7-147 
Tal