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[mkgmap-dev] [Patch] set map-version in img header

From Andrzej Popowski popej at poczta.onet.pl on Fri Jan 20 10:40:50 GMT 2017

Hi Gerd,

I call these values TRE parameters. They are 3 bytes at offsets 0x43, 
0x44, 0x45. I'm not sure, what is the real meaning of parameters. Same 
guesses are that it indicate routable/non routable map, general display 
priority, some parameters for navigation, general map type.

Info about faster routing probably comes form cgpsmapper. Table on OSM 
wiki looks wrong. Byte 0x40 is priority, I don't know if 3 byte is used, 
single byte works for me. Beside this priority, TRE parameters influence 
priority too, but differently on different GPS. It is like some GPS 
display City Navigator map over topo, regardless of draw priority in 
byte 0x40.

On Garmin maps byte 0x43 gets values 0 or 1, Byte 0x44 gets values 
3-4-6, byte 0x45 some values in range 1-43. Wiki shows it in reversed 
order. Last byte decide if map is visible in chartplotters, so probably 
define map type.

My idea is simply to copy values from original Garmin's map. So now 
mkgmap is using City Navigator parameters and option sets custom MPC map 
( https://developer.garmin.com/map-product-creator/overview/ ). You 
could set 3 values in option directly, but I'm not sure if it will help. 
Probably anybody who want to manipulate these values is able to use 
GMapTool or other patching programs to change it in img.

Best regards,

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