Steve Ratcliffe wrote:

Hi

On 04/09/09 10:16, Steve Hosgood wrote:

"I<hex number>.GMP". Does anyone know how the<hex number>  is derived
please? I guess that it is a bit-interleave of the latitude and
longitude of some reference-point in the tile, but it could be a
byte-interleave, or a nybble-interleave, or the interleave is done with
the number expressed in decimal or whatever.


I don't think there is any big significance to the names, they
can be fairly arbitrary strings.

Ah - not so! The .MDR file (not yet created by mkgmap) stores the names of subtile-files as 32-bit integers and expects the subtile files themselves to have names of the 'printf' format "I%07lX.GMP". See http://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin/MDR_Subfile_Format#MDR1_Subtile_List

There is a rumour on that wiki page that the subtile files can also be of a 'printf' format something like "%08ld.GMP", but I've not personally see that.

Steve