Hi Richard,
The approach that appears to have become a best practice among DataCite members and clients is to assign a resourceTypeGeneral of dataset and then use the Description property to indicate "map." I have found thousands of maps described this way. The other alternative would be to use PhysicalObject, but this is not what others are doing. Here is a typical example of the common approach:
https://doi.org/10.6084/m9.figshare.3568926
Perhaps we should consider "map" as an additional resourceType. What do you think?
--Joan Starr
Metadata Working Group Co-Chair