tkblatt - evaluating the TK25-sheetnumber from longitude and lattitude
The official institution "Deutsches Landesvermessungsamt" provides maps of germany in the relation 1:25000. Each map covers a range of 4km. Whole germany is represented by 100's of these maps, each of them has a number, the TK25 number.
tknr=tkblatt(8.2,49.8) // end of tkblatt