Thursday, 4 September 2008

Navman F20 Sat Nav device

Yet another Navman sat nav has come my way - an F20 (versionID 4.10.1029 BuildTime 2007-02-12, 09:38:57) and once again a different approach is required to access the relevant data files. The last Navman I looked at was a Windows CE device that became accessible using Mobile Device Centre in Vista. I have not been able to access this device the same way and I believe the underlying OS is Linux based. This site also states that the F20 is not running Windows CE. The case markings also do not disclose the precise model within the F series range. There are hidden service menus that will provide model and firmware information that are accessible by holding down the power and menu buttons together when powering on.

There is an SD Card slot which on the device I examined was not populated. The data was stored internally. I was not able to access this device as a removable USB storage device despite tracking down a driver. The only option left to me was to identify the storage within the device - luckily I discovered that the device has a micro SD card that is accessible without resorting to a full disassembly. The following pictures show how to access the card.







The memory card was formatted FAT16 and within the Navman/System folder I identified three notable files:
  • Recent.dat
  • Favver4.dat
  • Route.dat
RECENT.DAT stores up to thirty locations. The locations may be
-destinations that the user chose to navigate to
-they may be the location that the unit was at when it was turned on
-or the location the unit was at when the user chose to navigate to a new destination.
These locations are stored in records of 520 bytes in length. Each destination has its Lat/Long coordinates stored in 8 bytes starting at Record Offset 507. These are decoded by bookmarking in Encase as a 32 bit integer. The resulting values need to be divided by 100,000. In the UK Latitude will begin in the range 49-59 and is decimally notated. Longitude is in the range -5 to +1.6 ish. When bookmarking as a 32 bit integer Longitude is shown first and will often be a negative value (i.e. anywhere west of Greenwich).

FAVVER4.DAT possibly stores up to 200 user entered favourite destinations. These favourite destinations are stored in records of 1508 bytes in length. Each destination has its Lat/Long coordinates stored in 8 bytes starting at Record Offset 352. These are also decoded by bookmarking in Encase as a 32 bit integer and dividing each value by 100,000. I also established that the first location stored within this file was the User inputted Home location.

ROUTE.DAT I speculate is used to store the origin of the last navigated journey. Coordinates can be found at record offset 507 however in this particular device no data was found in this file.

I have an Enscript kindly coded by my friend Oliver Smith over at Cy4or to parse the recent.dat file. Please email me if you need it.

Along with the F20 I have also examined a Navman iCN 330. This unit is similar to the Navman iCN 310 I wrote about earlier. This device had it's notable files stored upon an SD card also. Notably all the flash media cards I have examined that originate from Navman devices did not contain any relevant data within unallocated clusters. This suggests that in some cases a manual examination (i.e. photograph display whilst device is turned on) may suffice.

Another issue I have encountered is how to test on these devices. On TomToms it is possible to clone the memory cards and use the cloned card for testing. This is not possible with the Navman devices I have seen. When you run the Navman with the cloned card you quickly receive an eror message No Map Data or similar. It appears that Navman has some anti copying features built in that utilise the flash card's CID number (which I believe is stored within a non host accessible area of the flash card). As each card has a unique CID number cloning is impared.

References
http://navmanunlocked.wikispaces.com/Unlock
http://www.sdcard.org/about/memory_card/pls/
http://duff.dk/navman/
http://www.gizmondoforums.com/forums/index.php?showtopic=5366

3 comments:

Emee said...

Great guide, one for the collections. Thanks

Anonymous said...

These things are so trivial to open that it is hardly worth defacing the back for. Undo the two screws at the bottom and then wriggle a screwdriver around between the two halves of the case until the plastic clips come free. It is next to impossible to snap them off.

Anonymous said...

Having struggled to find a USB driver for this device and then once loaded it still would not recognise the sat nav I came across this guide. Absolutely brilliant! Having contacted the author the supplied enscript worked in a flash. Thanks