Hi,
it's less a problem to know how gmp files or sections are structured. That is
known quite a time now. The
problem is the internal data structure of elements in these maps. That is how a
polyline or point is stored.
With every map Garmin produces new container types. Reverse engineering stopped
at an early stage,
because the knowledge is suffcient to build own maps.
Thus even if a decoder honores the GMP section, it will fail to decode most of
the stuff in that section,
because unknown data containers are used.
Oliver
> I've read about the NT format and the fact that the map data is exactly the
> same in a NT file and in a Not-NT one. But internally they are located at
> different place so Qlgt is not able to know where to read the information
> inside the NT file.
>
> Earlier Jose Luis Domingo made an attempt to solve this, and he said:
> >At the point the IMG FAT is processed, I seem unable to know what's the
> >
> > offset to the GMP header start, and quite don't get how to create "fake"
> > FATblocks for the contained standard headers, as if they where real
> > subfiles described in the FAT, and not subfiles pointed to from the GMP
> > header offset list.
>
> Also testlelelala has been working in this, and he has pointed to other
> informartions in other forums...
>
> Well , Good news!! it seems that in one of thoses forums (1) they have
> already solved this Issue, and in addition some one (kunix) has created a
> program which can locate these subfiles and extract them. The good news are
> that this program and the source-code is available on sourceforge:
>
> http://sourceforge.net/projects/processgmp/files/
>
> I'm not thinking about extracting and converting Nt files, but focusing in
> how this program locates the start of the subfiles.
>
> Unfortunately I do not the knowledge to go ahead with this, but I think
> that this reference would be very useful if someone wants to try it.
>
> Reading Nt format would be a very appreciated feature in QLGT.
>
> Hope it will be useful
>
> -----
> (1) http://www.gpspower.net/...
> <http://www.gpspower.net/creating-maps/302614-convert-garmin-img-pseudo-nt-n
> on-nt-i-know-its-possible-but-how-solved-4.html>
>
>
>
>
> 2013-08-14 0:22 GMT+02:00 Jose Luis Domingo Lopez <
>
> qlandkart...@24x7linux.com>:
> > On Monday, 05 August 2013, at 22:17:53 +0000,
> >
> > testlelelala wrote:
> > > Hi Jose, it's been a long time but I'm with the same questions, take a
> >
> > look
> >
> > > at this post about gmp headers etc...
> >
> > http://www.noeman.org/gsm/creating-maps/302614-convert-garmin-img-pseudo-n
> > t->
> > > non-nt-i-know-its-possible-but-how.html.
> > > Only the headers are changed all other info remain intact!!!
> >
> > Hi testlelelala, good to know someone better skilled and much more
> > dedicated than me to that was able to make my guess into reality.
> >
> > It looks like things were as I supposed / guessed / found out, and at
> > least
> > those quasi-NT Garmin maps generated with commonly available tools are
> > little else than normal Garmin subfiles packed into a GMP header
> > (subfile), and the resulting subfile the one and only subfile being part
> > of
> >
> > the .IMG file being distributed. Those files look like the following:
> > gmt v0.8.143.714b CC BY-SA (C) 2011-2013 AP www.gmaptool.eu
> >
> > Input file: 50250484.IMG.
> >
> > File: 50250484.IMG, length 2342912
> > Header: 30.04.2012 16:36:27, DSKIMG, XOR 00, V 0.00, Ms 0
> > Mapset: 0484 BUITRAGO DEL LO
> > fat: 1000h - 1200h - 2000h, block 2048
> > maps: 1, sub-files 1
> >
> > Sub-file fat length
> >
> > 50250484 GMP 1200h 2333666
> >
> > GMP: TRE RGN LBL NET NOD
> > map 2fec2f4 (50250484)
> > date 25.04.2012 22:23:46
> > priority 31, parameters 1 3 17 13
> > levels [14,15,18,20,21,23,24], zoom [86,5,4,3,2,1,0]
> > N: 40.999925, S: 40.833199, W: -3.854077, E: -3.520689
> > ..MapTk 3.2
> > CP 1252, Western European
> >
> > Map length s-f CP prio PID FID name
> >
> > 50250484 NT 2333666 1 1252 31
> >
> > However, as I can't manage to get GMapTool to split the IMG file into the
> > subfiles contained in the GMP subfile, I can't test your approach with
> > these particular maps, which may or may not include further changes.
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