The GPX-File is used as the universal exchange format for GPS devices.
The KML-File is used for Google-Earth.
The OVL-File is used for digital topographic maps.
The ASC-File is the universal collection of coordinates as text (ASCII-Format).
Definitions in the ASC-File:
TURM = completely reconstructed tower
TURMGRUND = Ground plan of the tower recognizable or reconstructed
TURMRESTE = Debris mound recognizable
K-KASTELL = Small fort with reconstructed pieces of wall
KK-RESTE = Small fort recognizable as elevation
KASTELL = completely or partially reconstructed appearance
KASTELL-R = Remains or elevation recognizable