Idea from http://mathematica.stackexchange.com/questions/18375/world-plot-without-borders-between-countries:

ds=Import["http://pubs.usgs.gov/of/2006/1187/basemaps/continents/continents.zip","SHP"]

polys=Cases[ds, _Polygon, ∞]

vs=Union[Cases[polys, {lat_Real, lon_Real} :> v[lat,lon], ∞]]

es=Union[Flatten[polys /. Polygon[l_List] :> MapThread[e, {l,RotateLeft[l]}]]]