TOP10vector 
CHECK-PLOTS 
CHANGE-ONLY 
  
  
  
  
  
  
  
  
A1 OLD 
B1 DELETIONS 
  
C1 DELETE 
  
  
  
  
  
  
  
  
  
A2 NEW B2 ADDITIONS C2 ADD 
Legend: 
a NODE BUILDING 
TOPOGRAPHIC EDGE GRASSLAND 
DITCH CROPLAND 
  
ROAD 
  
  
  
Figure 6 Change-only information 
The area on which the new house appears is changed 
from cropland to grassland. This change appears in both 
AREA-files ATTRIBUTE. Only the new attribute value 
(grassland) needs to be checked. Therefore, this area only 
appears on the checkplot B2. The area appears in both 
change-only files. 
The attribute change of the line appears in both BAS-files 
ATTRIBUTE and will appear on both checkplots and 
change-only files. The feature with the old attribute value 
is plotted, because the topographer has marked this 
feature on the film during the reconnaissance survey. 
The area-split results in changes that appear in both BAS- 
files GEOMETRY. The structural changes can be filtered 
to get the BAS-file FILTERED(add), which contains the 
added edge to split the area, displayed on the checkplot 
B2. The roadside is split into two edges and do not 
appear on the checkplots, but are included in the change- 
only files. 
The area-split also results in changes that appear in both 
AREA-files GEOMETRY. The deleted areas are not 
898 
plotted. All changed areas are included in the change-only 
files. 
As the example shows, changes in the geometry of line 
features will cause, of course, changes in areas as well. 
It is also clear that change-only datasets do not only 
contain changes caused by real world field changes. The 
existence of other categories can not be avoided. The 
TOP10vector-user-forum will be the obvious group to 
discuss items like this. 
In order to facilitate the exchange of change-only 
information, the application of unique feature identifiers 
are currently under study. Research and interaction with 
users is necessary to develop a revision infra-structure 
which is beneficial to all parties involved. 
From a technical point of view, the update process and 
the production of change-only datasets are rather 
straightforward. The challenge is to manage and control 
the process. During the reconnaissance, all topographers 
should apply the same data collection rules. During 
digitizing, only changes should be captured. However, it 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996