7. ALTERNATIVE METHODS 
Although the described system is successfully 
implemented, alternative methods are continuously 
considered to achieve an efficient production system. 
Alternatives can be divided into alternative data sources 
and new technologies. 
7.1 Updating through alternative sources 
Field changes are captured using aerial photographs. 
However, most topographic changes are captured by other 
institutes as well. In The Netherlands, a Large Scale Base 
Map at scale 1:1,000 exists, which is maintained by 
regional public-private partnerships. This map is 
continuously updated and may serve as input for 
TOP10vector. TDN is investigating this method in order 
to shorten the revision cycle. 
7.2 Updating through new technologies 
Other methods of updating are also under consideration. 
The first one is updating using stereo-workstations. The 
topographers could use these workstations in order to 
capture field changes behind their desk and carry out a 
short field completion. This has an enormous impact on 
the organisation. Advantages and disadvantages have to 
be considered seriously. 
Another method is updating in the field using notebook- 
computers. Orthophotos can be loaded and the 
topographer can digitize the field changes directly in the 
field. This will be investigated in the near future. The 
disadvantage of this method is the high demand on 
photogrammetry during a short period of time. Before the 
topographers can go for the reconnaissance survey in the 
summer time, all aerial photographs (covering 25% of the 
country) should have been transferred into digital 
orthophotos. 
8. CONCLUSION 
According to TDN, digital updating in itself is not 
considered very different compared to the initial 
TOP10vector-production. The challenge is to control the 
process. Topographers and operators should work in an 
uniform way. Another challenge is to deliver change-only 
datasets to users in order to facilitate their data revision. 
At the same time, users ask already for higher update 
frequencies. Their wishes can be fulfilled by using data 
from other sources to update TOP10vector. However, for 
quality assurance, the planned four year revision cycle 
based on aerial photography will continue to exist. 
At the end of 1997, TDN will reach a milestone by 
having a nationwide digital coverage at scale 1:10,000. 
900 
Digital updating will then be the normal production 
method, while new technologies will lead to other 
innovations of TOP10vector-production. 
9. ACKNOWLEDGEMENT 
The professional advice and support of Bert Kolk is 
greatly appreciated. I also would like to thank Jeroen van 
Gelder for the illustrations. 
10. REFERENCES 
Van Asperen, P.C.M., 1996, Topographic Databases in 
Europe - National Mapping Agencies Go Their Own 
Way, Geomatics Info Magazine, Vol. 10, nr. 2, pp. 17- 
19 
Birth, K., 1995, ATKIS database revision in Nordrhein- 
Westfalen, In: Workshop on revision of digital 
topographic databases, CERCO Working Group IX, 
Emmen, The Netherlands 
Geudeke, P.W., 1993, From base database to core 
database - the Topographic Service as producer of the 
core database 1:10,000, Kartografisch Tijdschrift, Vol. 
19, nr. 2, pp. 24-28 (in Dutch) 
Gray, S. (ed.), 1995, Updating of complex digital 
topographic databases, OEEPE, Official Publication No. 
30 
Kolk, E., 1995, On the road with TOP10vector - a 
nationwide medium scale geographic database, NGT 
Geodesia, Vol. 37, nr. 1, pp. 13-19 (in Dutch) 
Lemmen, H.J., van Oosterom, P.J.M., 1995, Efficient 
and Automatic Production of Periodic Updates of 
Cadastral Maps, In: Joint European Conference and 
Exhibition on Geographical Information, The Hague, 
Vol. 2, pp. 137-142 
Opie, R., 1995, The Dutch Topographic Survey: form 
ministry to marketplace, GIS Europe, Vol. 4, nr. 3, pp. 
17-19 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
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