SRE 
IQQ UU a RENNES 
ERU 
  
TTR RE 
| 
E 
Bi 
Ei 
I 
Bl 
| 
I 
DOE 
  
  
  
  
‚ Om 
SCIO, y, 25) 
  
  
ANN VNVVVVNN 
  
Fig.1. Plane containing tangent points projected on 
ZY plane. 
Equation of this straight has the form: 
A Ze 
Zz 
  
2 2 
nn 2 (2) 
Theoretical shape of cooling tower axis, observed 
from the camera stand SCO, V3 2p) » projected on the 
plane XZ, is descripted by a hyperbol equations: 
x? 
a? (y2b?-a?z?-a?b?) 
yàb?-a?z2 
  
  
(3) 
a?b?zà 
y2b*(y2b?-a?z?-a?b?) 
(b?yj-a?z$)? 
7 
m 
  
  
assuming z,#0 and x? + y! > al ; 
For calculations of the real shape of cooling tower 
surface along the tangent line from a given stand and 
for scaling of photogrammetrical model, there is used 
the determined angle e, taking into account the given 
elements of external and internal orientation of the 
picture. A11 calculations, taking into consideration 
the varying shell thickness, are carried out using 
COOLMONO program, whereas graphic results 
presentation by means of GRAPHER program. An example 
of determination result of geometric imperfection, 
carried out from one stand are shown in Fig.2. 
For determination of deformation alterations of 
cooling tower surface, the real shape of which had 
been determined during primary measurement, the most 
frequent applicated is the time parallax method, 
taking into consideration the scale alterations 
depending from height of the point observed. 
2.2. Stereophotogrammetric method 
Determination technology of cooling tower shell 
330 
external surface shape is most often based on 
independent models method. Application of this method 
is possible in the case of univocal identification of 
points observed on the surface and control points 
which allow to determine the corrections of elements 
of external orientations. 
Precision analysis of space coordinates determination 
is carried out taking into consideration the 
differences of observation points coordinates in 
strips of model covering and the differences of 
control point coordinates (Mierzwa 1991). In the aim 
as to ensure the required precision * 10 mm of shell 
shape determination in observation points, the camera 
stand and control points coordinates should be 
determined by means of a geodetic method with an 
accuracy not less than + 3 mm (Mierzwa 1991). 
Stereophotogrammetry gives great possibilities of 
future and easy processing of calculation result, 
taking advantage of existing packages of computer 
graphic e.g. SURFER, GRID, GRAPHER ect. When using 
this programs, one can freely interpolate the 
coordinates net, adopted for evaluation of stability 
and strength by means of finite elements method. 
Application examples of existing programs for 
calculations and graphics presentation of 
investigation results are shown in Fig.3. and 4. 
(Mierzwa 1991, Owczarzy 1991). 
3. FACTORS INFLUENCING CHOICE OPTIMUM METHOD 
The presented elaboration methods and examples of 
their applications are characterized by both 
advantages and also disadvantages which in dependence 
on cooling towers characteristics can have a decisive 
influence on choice of optimum method. 
The monophotogrammetric method (one-picture 
photogrammetric method) can be applicated with 
success to investigations of deformation alterations 
along determined meridians. The photogrammetric 
pictures are being taken from the constant cammera 
stands during each measurement cycle with 
preservation of identical elements of internal and 
external orientations. Monomial observation points on 
one straight are being observed without necessity of 
their signaling by means of time parallax method. 
Precision of these determinations is valuated in 
limits of + 5 mm. While determinating geometric 
imperfections using monophotogrammetric method, there 
occurs the necessity of hyperbola theoretical 
parameter calculations for each point independence on 
imperfections’ value determined at first calculation 
stage. It results from variability of scale 
alteration coefficient, caused by surface 
irregularities which contains tangential points of 
observation radii with cooling tower external surface 
determined by equation (2). In particular case of 
occurrence of big and differentiated cooling tower 
surface deformations in parallel planes, the 
monophotogrammetric method can lead to improper 
imperfection determination. In spite of difficulties 
in current formulation of mathematical model while 
determining the real shape of cooling tower external 
surface, the reinforced concrete building specialist 
highly appreciate the result and presentation way, 
when using monophotogrammetric method. 
Stereophotogrammetric method is completely univocal 
in respect of mathematical model. This method allowed 
to realize the precision evaluation on the base of 
measured control points and its considerably 
simplifies the calculation process. Exactness of 
determination of real surface shape is contained in 
limits of + 10 mm. Difficulties in application of 
this method occur in case of lack of any signal 
points especially after overhaul works, when the