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As far as our practise goes the past 20 years the precision in
giving coordinates depends on the scale of the map.
 
Topographic maps (1:10,000 - 1:25,000 - 1:50,000) give
coordinates up till geographic seconds (sexagesimal) so we
catalogue them. The same for townplans of Amsterdam and The Hague
1:1,000. If not mentioned on the map we use geographic minutes
for scales 1:10,000 - 1:500,000 and degrees for over 1:500,000.
 
We always use Greenwich as prime meridian as the coordinates are
meant for retrieval purposes. Centesimal degrees therefor are
converted to Greenwich sexagesimal.
 
In structured fields and notes is remarked that the map shows
Greenwich or other prime meridians. Not only French maps carry
their own prime meridian (Paris), but e.g. also Spanish maps
(Madrid) and probably several others. The Paris prime meridian
was in the third quarter of the 19th century e.g. also used on
maps in Petermann's Geographische Mitteilungen, a famous German
geographic journal.
 
For further information look into: "Cartographic materials : a
manual of interpretation for AACR2" (1982), probably to be gotten
from the American Library Association.
 
Jan Smits
Map Curator Koninklijke Bibliotheek, National Library of The
Netherlands
E-mail: [log in to unmask]