The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
( Fugure3 ) 
Once the topology is created, buildings, forest, bridge, river etc. 
are described by the closed polygons. 
In consideration of the client’s requirement to data accuracy, 
what we must done during capturing data is that the object’s 
classification should be correct, the snap precision is up to grade, 
no omission and missing object. And that creating the topology 
to ensure z-value is the same at nodes of road and terrain data 
intersections, all those will be performed in data editing process. 
Hereinafter the operation method of data edit will be introduced. 
- A polygon can touch another polygon. That means they share 
the same points. (See Figure 4) 
- Tangential point between two polygons is not allowed. (See 
Figure 4) 
- Polygon A can be fully inside another Polygon B. (See Figure 
4) 
Intersection on itself 
Intersection between 2 polygons 
Polygon A is: [12J.6.7] 
Polygon B is: (3,4.5,6] 
So they share points 6 and 7. It'the polygon A 
was described by i 1.2.6.7]. this means that 
point 3 of polygon B is tangential. So. In tins 
case Polygon A is wrong 
If B [1,2,6.7.3,41 and A [$,6.7.8]. the 
description is wrong because points 8 and S 
are inside B and 7 and 6 are touching B. 
The polygon A should be described by 
[I.2ASJU.4J 
The right description for this configuration is : 
A - 15.6.7,81 
(Figure 4) 
4.4. The data editing 
It can be completed in five steps: Step 1, Check layer and color, 
flying point and line; Step 2, Pick up DEM data and process 
data error; Step 3, Pick up all polygon features including tree 
hedge to create topology relations; Step 4, Pick up 3D point 
from 3D data and the polygon from 2D data separately and run 
ARSCCHECK to detect error, then modify them; Step 5, 
Transfer DXF format under the CAD 2000 according to the 
client’s requirement, then deliver the data to the client. 
Step 1. Check layer and color, flying point and line: Its main 
purpose is to unify layer and color, to modify the wrong layer 
phenomenon probably appearing during capturing the data. 
Detect if there is flying point and line in data via front view. 
- Holes cannot be totally located within another polygon. (See 
Figure 5) 
(Figure 5) 
Step 2. Pick up DEM data and process data error: Modify 
the dangling and make nodes to terrain (ground height), road 
and railway so as to ensure common nodes that should be 
shared at junctions of DEM data with same z-value. 
Step 3. Pick up all polygon features including tree hedge to 
create topology relations. This is the key point in data editing 
process. First, modify dangling by using 2D data to the object 
elements in 3D data. Then, pick-up all polygon elements 
including tree hedges and transform them into 2D data. Make 
nodes to those 2D data, after that, modify dangling again. 
Because if the dangling is modified well or not will have 
relations with the veracity of creating topology. After 
completing dangling modification, the closed polygons can be 
created layer by layer under GeoGraphics. 
- A polygon must not present sharp angle less than 5°. Refer to 
Figure 6. 
Step 5. Transform the edited 2D and 3D data into DXF 
format under the CAD 2000, then deliver the data to the 
client. 
Step 4. Run ARSCCHECK to detect the error and correct 
them. The topology should meet these requirements: 5. FREQUENTLY ASKED QUESTIONS AND 
QUALITY CONTROL METHOD 
- A polygon cannot intersect itself or any other polygon. (See 
Figure 4) In order to capture the high-resolution data, Siradel drafted a 
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