Hello trid users,
some days ago i run out of disc space on my Windows System. About
16 GB at c:\ProgramData\Garmin are occupied by Garmin Express, a
software to update Garmin GPS navigation devices. When i run trid on
downloaded maps these are only described as " Unknown!" ( see
appended output/trid-old.txt).
Unfortunately there exist no official documentation by Garmin, but some
people have reverse engineered many aspects of that file format. This is
information is found on wiki of street map.
Characteristic for such Garmin sub file maps is the up cased phrase
"GARMIN " near the beginning.
At the beginning the header length is stored. Because the size of the
header is not large, this info can be used to distinguish maps from
ASCII text file with GARMIN phrase. So often the upper byte of header
length is null.
After the Garmin phrase 3 up case letters are stored for different sub
file. So for sub tile of the larger area these facts are expressed by XML
construct:
<Bytes>004741524D494E20474D50</Bytes>
<ASCII> . G A R M I N G M P</ASCII>
<Pos>1</Pos>
according to open street map wiki by line:
<RefURL>
https://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin/GMP_Subfile_Format</RefURL>
File named extension is same as 3 character phrase. This is expressed by
line:
<Ext>GMP</Ext>
With the new 10 trid definitions all examples are now described ( see
appended output/trid-v-new.txt). TrID definitions and output are stored
in archive garmin-maps.zip. I hope that my XML files can be used in
future version of triddefs.
With best wishes
J?rg Jenderek
