In: Paparoditis N., Pierrot-Deseilligny M„ Mallet C.. Tournaire O. (Eds). 1APRS. Vol. XXXVIII. Part 3A - Saint-Mandé, France. September 1-3. 2010 
than in case of thermal inspection of the buildings, where 
radiometry of the texture is very important. Before combining a 
texture from more images the changes of radiometry in whole 
sequence should be investigated. If they are remarkable the 
textures should be extracted from one image only, even with 
lower resolution. Radiometric adjustment of the texture from 
multiple images in case of thermal inspection shouldn't be 
applied at all. 
Although the distance factor (d) and surface orientation angles 
(y x , y) in the quality equation reflect the effective resolution of 
texture, they should be considered separately. When the angles 
y x , y. are large, the resolution of the texture is not only low, but 
also inhomogeneous. For avoiding this situation the coefficient 
a 3 should be set higher then a 2 . 
4. EXPERIMENTS 
4.1 Data overview 
During the flight campaign a helicopter flew four times above 
the test area TUM recording a sequence of oblique images. This 
dataset was taken additionally and simultaneously to a laser 
scanning during a flight campaign (Hebei & Stilla, 2007). 
Afterwards four subsequences (stripes #1, #2, #3 and #4) 
representing each of the four flights were cut out. The helicopter 
trajectory and the stripes’ directions are shown in Fig. 4. The 
intersection of the trajectory is located above the centre of the 
test area. 
b) 
X-=0° y=25° d,=0,73 
qy-i=0,88 
qÿ.2=0,89 
qÿ.3=0,82 
frame 2128, #1 
Figure 5. Textures of the same roof with different quality 
factors, qjj.] was calculated with aj=a 2 =a 3 =U qy-2 with a,=a 2 =l 
and a 3 =3; qy.3 with a/=a 3 = 1 and a 2 =3 
a) 
X=l° X=30° dy=0,17 
qy-1=0,68 
qy- 2 =0,75 
qy- 3 =0,47 
frame 2018, #1 
/ v =l° x=32° dÿ=0,52 
qy-1=0,79 
qij_2=0,81 
qy- 3 =0,68 
frame 2128, #1 
Figure 4. Flight trajectory over test area TUM 
(Hebei & Stilla 2007) 
The inclination angle of the optical axis is approximately 45°. 
Images were captured with the AIM 640 QLW FLIR infrared 
camera with the frame rate of 25 images per second. The image 
resolution is 640 x 512 pixels. 
4.2 Results 
qy-1=0,5 8 
£=84° X=l° dÿ=0,62 qy. 2 =0,39 
qy.3=0,60 
Figure 6. Textures of the same wall with different quality 
factors and from different stripes. For qy_i, q^, qy.3 - see Fig. 5 
For presentation of the proposed quality measure some 
exemplary textures with different qualities ware extracted 
(Figures 5, 6 and 7). The quality measures q^.j - were 
calculated with a choice of coefficients a ]r a 2 and a 3 .