III. The German-Danish type with a fairly wide topographic ränge for the ground cover
(types of Vegetation) and the orography.
IV. The Italian type with the accent on relief and a remarkable narrow ränge for
büilt-up areas and ground cover.
V. The Swiss type with an excellent representation of relief but on the other hand a
narrow ränge for other terrain elements.
The width of the topographic ranges in the various maps is partly the result of
taking a legend which is representative for one particular type of landscape prevalent
in a country and making it a norm in that country.
Through international co-operation one should be able to bring together into one
continuous topographic range-legend all the well worked-out individual national
topographic range-legends. The one continous topographic range-legend could then be
applied international^. For this purpose one would first have to classify a number of
topographic norm landscapes.
The international co-operation which will be required for this type of venture can
best be placed under the auspices of an ICA-Commission.
When in 1967 the 'Mijnwet Continentaal Plat' (Continental Shelf Mining Act)**
became law, the Dutch could Start exploring their part of the Continental shelf for
natural resources such as oil and natural gas. Before this occurrance a substantial
amount of sand was already obtained for various purposes along the coast.
In November 1967 the geological exploration of the upper layers of the sea floor
was made the responsibility of the 'Afdeling Havenmonden van de Directie Beneden-
rivieren van Rijkswaterstaat' (Department of Harbour Entrances of the State Water
board). In co-operation with the 'Rijksgeologische Dienst' (State Geological Service) a
Start was made with shallow drilling in the sea bottom with a Zenkovitch apparatus.
This apparatus takes bottom cores up to a depth of three meters. With this
276 K.N.A.G. Geografisch Tijdschrift VI (1972) Nr. 3
CONCLUSIONS AND RECOMMANDATIONS
Dr. J.J.C. Piket, lector Roman Catholic University Nijmegen.
NOTES
1. Koeman, C., The principle of communication in cartography. Invited paper, Stresa 1970.
2. Wrenn, C.L., The English language. London 1962.
E .A. KASEMIER and P.W. POSTEMA*
The Mapping of the North Sea Documentation Sheets 1 SO 000 of the Dutch Part
of the Continental Shelf
CONTINENTAL SHELF RESEARCH
