There are two file formats for Map data called "PSF".
This file format is not specified yet, no details known about.
The Medion GoPal navigation devices are shipped with maps in files extended by .PSF. This format is some kind of binary-mix.
Medion, vendor of the device and maps, replied on my request as following:
Zu unserem Bedauern ist die Nutzung von eigens erstellten Karten mit dieser Software nicht möglich, dieses Feature wird von der Software generell nicht unterstützt. Ebenfalls können wir Ihnen nicht mit einem Konverierungsprogramm dienen.
(translation in english: The usage of self-created map data is not possible. This feature is generally not supported by the software. Additionally, we cannot offer you a converter software.)
Hacking the file format
I'm not skilled for that, but I did a few tests, though. :)
The device checks the MD5-Hashes, stored in a file in the root directory of the flash card. This hash has to be recreated after changes made to the data file.
The file format consists of some text and a bunch of binary data. The text contains (afaics) all the motorway exits. But *not* plain city names or street names. Many street names cannot be found in plain text and seem to be encoded somewhere.
Supported features of those maps (maybe incomplete):
- display and routing (of course)
- lane assistant
- text-to-speech (don't know if the map file has something to do with that)
- speed limit imformations