International Archives of the Photogrammetry, Remote Sensing and Spatial Information 
  
= 
1 
| 
| 
| 
| 
i 
| 
p 
wn 
       
  
9 
uA 
T 
— 
o 
T T 
m 3€) Mom 
Won gu Hn ug m wo] d 
J 
e 
Std.Dev (mm) 
  
  
  
Distance (m) 
Figure 2: The object point co-ordinate deviation respect 
to object distance. Each curve illustrates the imaging con- 
figuration with certain length of radius. 
3 ARRANGEMENT OF EXPERIMENT 
In the first field demonstration the arrangements of the imag- 
ing constellation were as similar as possible to the simul- 
ation environment. Approximately 30 photos were taken 
per image block and camera was nearly perpendicular to 
the supporting rod. The effort was made to take photos 
with as equal-angled as possible. Despite of that, received 
initial values for block parameters were not good enough 
and there were real difficulties to get iteration converge. 
Finally, the image block estimation could be computed, 
but residuals were not acceptable. Systematic errors in re- 
siduals were clearly visible and most of the residuals were 
vertically directed. This indicated that either camera cal- 
ibration was not correct or the requirement of projection 
centers lying on the same plane was violated. The lat- 
ter was suspected and therefore a new more controllable 
imaging system was designed. 
3.1 Motorized imaging system 
In the first experiment, the revolving rod was attached to 
tripod with a rotary actuator without ball bearing and no 
precise scale was present to assist in evaluating the approxi- 
mate rotation of the rod between shots. To prevent abnor- 
mality in height of the projection centers during imaging 
and in order to receive better initial values, a ball bear- 
ing supplied rotation system was designed and assembled. 
Better rotation control was achieved by supplying the sys- 
tem with a worm gear and a step motor (Figure 3). Step 
motor was controlled by computer to rotate the camera 
with equal-angled steps. Camera was also triggered auto- 
matically under computer control. 
This type of system design provided fully automatic im- 
aging without human intervention. Camera setups were 
fixed into constant focus (infinity) and the aperture was 
also predetermined according to setup values used in pre- 
vious camera calibration. 
3.2 Experiment in real conditions 
Next experiment was run in interior space in an entrance 
hall, which consisted of a corridor, two round columns and 
  
   
Sciences, Vol XXXV, Part BS. Istanbul 2004 
ok 
A4 
Figure 3: Step motor driven imaging system. 
  
a staircase (Figure 4). So the conditions were such that one 
could meet when carrying out a typical measurement task 
in interior space; blind angles, small angles between wall 
surface and viewing angle plus varying illumination. The 
maximum distance inside the area was approximately 40 
meters. 
E] 
LE 
EM 
i: 
3 
3 
+ 
Figure 4: The entrance hall where the experiment took 
place. 
The idea was to evaluate the system accuracy from the 
single imaging station. For the reference datum the tar- 
geted points were measured by a tachymeter. Tachymeter 
measurements were based on simple horizontal/vertical an- 
gles and a distance. Prism used in measurements was a 
typical big prism used in field work. So no special instrumen- 
tation was used. In tachymeter measurements there oc- 
curred some difficulties to get prism detected by tachymeter. 
This caused that in the final accuracy analysis it was some- 
times hard to evaluate, which discrepancies between pho- 
togrammetric data and reference data are a consequence of 
inaccuracy of photogrammetric data and which is due to 
unreliability of the reference data. 
The imaging was made at the same spot as tachymeter 
measurements. Rotation center of imaging differed only 
few millimeters from the tachymeter coordinate system. 
This was verified afterwards with a coordinate system con- 
version. Imaging was accomplished with computer con- 
   
  
   
  
  
  
  
    
  
   
     
  
   
   
   
    
   
   
   
   
   
   
   
   
   
   
   
   
   
  
   
  
   
   
   
  
  
   
   
   
   
   
  
  
  
  
   
   
     
   
  
   
  
   
     
  
Internatic 
trolled s 
was atta 
from the 
The cam 
values a 
sas allo 
camera. 
pus E-11 
The ima 
conditio 
took pla 
some im 
suréd. € 
reasonal 
vided th 
The targ 
image c 
source 1 
the oper 
racy. Th 
quence ? 
the searc 
LSQ-est 
best posi 
to extrac 
next ima 
always f 
sure that 
fer mucl 
the poin 
ping crit 
order to 
block, th 
template 
The sele 
ond bloc 
pair for | 
itial orie 
angles w 
The initi 
from coi 
The initi; 
measure 
with oric 
the first | 
second. 
At the fir 
ter an ac 
viation 0 
residuals 
On some 
and on o 
sistency - 
values. 1 
paramete 
this actic