[mkgmap-dev] MapSource crash with DEM: Maybe tdb file needs changes?

Mon Feb 5 11:48:43 GMT 2018

Hi

> It seems that mkgmap writes some constants that might be important, e.g. MapDetailBlock.java contains
> //01 c3 00 ff
> 			os.write4(0xff00c301);
> 			os.write(0);
> 			os.write(0);
> 			os.write(0);

I've just looked at this. No idea where any of those came from :)

I think those 7 bytes should be:

1 byte: unknown to me
1 byte: Maybe index into block 'S' (0x53)
1 byte: index into block 'R' (0x52) or zero if no block 'R'
4 bytes: a size that is generally related to the size of the file.

cgpsmapper and gmaptool set this size to 256 (and previously to 255)

Block R has the following structure:

   1 byte: index number, starting from 1
   n bytes: zero terminated string

There is probably only ever one of these.  Eg "Europe guide v1"
Gmaptool appears to create one of these with the name "All".

Block S has the following structure:

   1 byte: number, probably index into block R
   1 byte: number index in this block, starting from 1
   n bytes: zero terminated string name

eg: 1,1 "Region 1 - Aus/Switz/N.Italy"
     1,2 "Region 2 - France"
     1,3 "Region 3 - Germany/Czech Republic"
     ...

Unfortunately I think they have nothing to do with DEM as
maps without DEM have these.  There are lots of unknown
entries in the TDB header, there could be something there.

..Steve