The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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detailed specification and supplied a check program to check 
the data quality. So during the actual operation, the operators 
should pay more attention to the consistency between the actual 
production and specification so as to ensure the data’s geometry 
precision and integrality. In the production process, the quality 
control will be completed in two steps. One is correct objects 
classification, strict snap, no missing information in data capture 
process; The other is strict match and overlap between 2D and 
3D data, and correct topology in data editing process. The 
following is the frequent questions in the data production. 
5.1. Orientation 
The orientation precision will affect the precision of basic data 
directly. Therefore the orientation precision must accord with 
the design requirement. Usually, we adopt manual interior 
orientation, then import the aerial triangulation data directly, in 
this way, we can avoid from twice orientation error so as to 
ensure the orientation precision. 
5.2. Altimetry (ground height) 
Altimetry is the basic data to generate DEM, when its precision 
limits less than one meter, the following questions can appear 
frequently. 
5.2.1. The embankment is not complete or missing. 
Because the terrain (ground height) accuracy is required no 
more than one meter, only when the elevation difference 
between the top and bottom of embankment is less than one 
meter, the embankment can be ended. Even if sheltered from the 
construction, it should be described completely. Please refer to 
Figure 7. 
(Figure 7) 
5.2.2. The relation between the bridge and the embank 
ment is illogical. 
Please see Figure 8. 
Wrong Correct 
(Figure 8) 
5.2.3. Lack of breaklines behind the buildings 
This makes DEM data of part building falling under the ground. 
Please see Figure 9. 
5.2.4. Breaklines are crossed 
That the breaklines are crossed is also a common problem. This 
will cause DEM abnormal. 
(Figure 9) 
5.3. Road Capture 
When capturing the road, often appear two common problems: 
one is easy to make road classification confused. So first, we 
must understand road classification criteria correctly in design 
requirement. And we also need to know the traffic situation in 
the surveyed areas within the various countries or regions. 
Secondly, it must be noticed to capture data at intersections by 
using 3D snapping so as to assure they have the same Z-value at 
intersection. 
5.4. Clutters Data Capture 
The clutters’ data are also an important part of basic data to 
generate DSM, it is requested to close the polygon and form 
certain topology relation, and no any intersection exists among 
polygons. Please see Figure 10. 
5.5. Construction Classification 
It’s also easy to create error when classifying building. This