[mkgmap-dev] splitter, mapid

Wed Dec 19 06:43:34 GMT 2018

Hi Andrzej,

sorry, you totally lost me here. I fight with a cold since 8 days ;-)
I'll look at this again once I feel good. again.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Dienstag, 18. Dezember 2018 14:14
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] splitter, mapid

Hi Gerd,

yes, I got the formula after examining numerous Garmin's maps. I know,
that City Navigator is different, my guess is that next CN map gets next
free mapid. I'm not sure about marine maps and other new maps from Garmin.

It looks like the formula is easy to support up to FID 45744. For bigger
values you could take different strategy. The rules I know are following:

Mapid inside img data is 4-byte value, no problem here.

File names are independent of mapid, could be any arbitrary 8-digit
number (number from file name could be even written in TRE header, at
offset 0xCF).

Names of subfiles like 12345678.TRE can be written in HEX, in this case
you should use prefix 'I'. So 12345678.TRE is equivalent of
I0BC614E.TRE. Mapid 140.531.712 could correspond to I8605800.TRE.

My first suggestion is to limit --fid to max 45744. For bigger FID
option --mapid should be used.

Second proposition is to overlap mapid values for big FIDs, but with an
offset of 1024. So for FID > 45744 formula could be like this:

mapid = (fid - 19792)*2048 + 6316032 + 1024

--
Best regards,
Andrzej
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