The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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It was initially expected to extract a 1:500 map from the first 
flight images, as all the entities requested by technical 
specifications were clearly visible. Nevertheless details larger 
than 0.5 m must be metrically described, at this map scale. 
However, these details were sometimes hard to correctly 
represent; an example of this is the small chimney (shown in 
figure 4) that can only be plotted by zooming onto it. For this 
reason an attempt was made to realize both a 1:500 and 1:1000 
map scale: the achieved results are summarized in table 3. As 
shown, it is however possible to map at a 1:500 scale, just by 
zooming a little onto some details. In some ways, a GSD equal 
to 0.10 m can be considered the maximum suitable dimension 
for this scale mapping. 
Map Scale 
Group 
A 
Group 
B 
Group 
C 
1:500 
96% 
4% 
0% 
p 
1:1000 
100% 
0% 
0% 
p 
Table 3. Comparison between 1:500 and 1:1000 map scale 
It was expected to extract a 1:2000 map scale in the second 
flight (GSD=0.20 m). 
The possibility of extracting a 1:1000 map scale was evaluated 
but, as shown in table 4, too many entities, even though visible, 
could not be correctly plotted. An example is shown in figure 5 
where small pavements obviously appear very narrow even 
when large zooms are used. For this reason, it was decided to 
extract a 1:2000 map scale. 
Map Scale 
Group 
A 
Group 
B 
Group 
C 
1:1000 
90% 
10% 
0% 
V 
1:2000 
100% 
0% 
0% 
p 
Table 4. Comparison between 1:1000 and 1:2000 map scale 
2.3 UltraCamD Vexcel 
This flight was performed over the city of Graz in Austria, at an 
altitude of 900 m. The GSD dimension was about 8 cm and it 
was therefore expected to generate a 1:500 map scale from 
these images. All the map entities required for this scale map 
were recognized correctly and stereoplotted. The quality of 
these images was very high, as it is possible to see in figure 5. 
Small windows and chimneys on roofs are clearly shown (also 
in a stereoscopic view). 
This GSD dimension can be considered the optimal dimension 
in the 1:500 map scale. 
Figure 6. Urban area acquired by UltraCamD (zoom 1:1, 4:1) 
2.4 DMCZ/I 
These images were acquired during a flight which was 
performed at a height of 1200 m over the city of Lauria in Italy. 
The Ground Sample Distance was 0.12 m large. 
All the required map entities in the 1:500 map scale were 
recognizable in a first analysis. Nevertheless their dimensions, 
as in the previous case, were too small to be correctly plotted in 
a digital map even thought a 4:1 zoom was employed (see 
figure 6). A comparison between 1:500 and 1000 is made in 
table 5. As shown, it was not possible to' nifetrically represent 
too many entities. 
For this reason, the semantic analysis was performed in 
reference to the 1:1000 Technical Specifications. All the 
required map entities were detected and plotted with the 
necessary precision. 
2.5 3-DAS-l Wehrli & Associates 
This flight was performed at a height of 1000 m. The GSD is 
about 8 cm and according to the adopted methodology, it was 
expected to extract a 1:500 map scale. 
Figure 5. Urban area acquired by ADS40 2 nd generation, 
GSD=0.20 m (zoom 1:1,4:1)