want to export contours of denmark to osm

We do not store contour lines in OSM because they cannot be surveyed by individuals (and they would make our database quite a bit larger!). What we usually do is when we want to draw a map with contour lines (like e.g. www.opencyclemap.org), we mix OSM data with the contour lines from another source - without ever uploading the contour lines to OSM.

Welcome rasm866i! Very nice that you want to enhance the OSM data, however, ...

(Update) For some reason I thought of coastlines (contour lines of landmass...). Here, height data is meant, as we do not store them (as Frederik pointed out), all further information is not relevant anymore.(/Update)

The process of adding a whole bunch of data from somewhere else to OSM is called import. There are many things to think about even before you come to the technical aspect. You can read about it at our documentation wiki about "Imports". Also see other questions tagged with "import".

The most important things:

• license - are you really allowed to import the data to our database (copyright info) or is it just "free" (free of cost)? E.g. commercial use must be allowed.
• does the community want the import. Does it help us? How and what to import of it - since there is existing data. Do you want to throw the existing data away? Probably it is more useful to just use the data in some cases and manually(!) adjust / replace parts of the existing data, if the governmental data is really better.

Most of these details of your idea should be discussed somewhere else (mailing list, forum, wiki ...) but probably not here.

Please use the "add a comment" function to comment! If you want to add more info to your question, please "edit" your original question.