[mkgmap-dev] RGN Section 6 and part of TRE Section 7

Thu Mar 16 13:23:25 GMT 2023

Hi Thomas

Have you looked at the code and output from the mkgmap display tool? It
was available for svn at 

https://svn.mkgmap.org.uk/mkgmap/display

but I can't access it at the moment

Ticker

On Wed, 2023-03-15 at 19:57 +0100, thomas at ankarsvik.nu wrote:
> Hi,
> 
> Sorry if this is slightly of topic.
> 
> This is a typical dump from a file without Huffman encoding. (RGN 
> Section 5)
> 
> TRE - Section 7 dump
> 
> 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16
> 17 
> 18 19 1A 1B 1C
> ---------------------------------------------------------------------
> -----------------
>   Sec 2     | Sec 3     | Sec 4     |  |Columns related to RGN
> Section 6
> 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 0B 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 17 00 00 00 00 00 00 00 06 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 24 00 00 00 12 00 00 00 0C 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 32 00 00 00 26 00 00 00 12 00 00 00 01 00 00 00 00 06 00 00 00 13 00
> 00 
> 00 15 00 00 00
> 41 00 00 00 3D 00 00 00 18 00 00 00 00 06 00 00 00 13 00 00 00 15 00
> 00 
> 00 1B 00 00 00
> 
> All rows except the last row is related to it's sublevel, Row 2 to 
> sublevel 2 and so on.
> 
> Explanation to last row
> 41 00 00 00 = RGN Section 2 Length
>              3D 00 00 00 = RGN Section 3 Length
>                          18 00 00 00 = RGN Section 4 Length
>                                      01 = Flag (Not allways first 
> sublevel per zoom-level)
>                                         06 00 00 00 = End of first
> part 
> RGN Section 6
>                                                     13 00 00 00 = End
> of 
> second part in RGN Section 6
>                                                                 15 00
> 00 
> 00 = End of third part in RGN Section 6
>                                                                      
>      
>    1B 00 00 00 = Total Length of RGN Section 6
> RGN Section 6 dump
> 
> 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
> -----------------------------------------------
> 0B 11 72 2C E5 36 19 11 04 4C 91 D7 FC 4B 11 BE
> CC 8F 1E E0 00 0B 11 72 2C E5 36
> 
> 0B 11 72 2C E5 36                       : 0B >> 1 gives following
> byte 
> length of 5
> 19 11 04 4C 91 D7 FC 4B 11 BE CC 8F 1E  : 19 >> 1 gives byte length
> of 
> 12 decimal
> E0 00                                   : Seen E0 00 in other files
> 0B 11 72 2C E5 36                       : 0B >> 1 gives following
> byte 
> length of 5
> 
> Shifting the first byte to give following byte length seems to be
> valid 
> if the value is odd.
> This is also valid within a byte array (amount of bytes in a
> sublevel) 
> stated in TRE Section 7.
> 
> 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
> -----------------------------------------------
> 15 11 70 7C 76 6F ED 1A 3E 2F 34 15 11 E0 AF F7
> 12 A7 CB CD 17 34 0D 11 8C 5A F9 2F 01 0D 11 E0
> CF 70 D9 3A 0F 12 68 7C CC E6 F0 00 0D 12 E0 1E
> 80 79 1F 11 11 D4 0B 3E 19 00 17 0C 0D 01 78 B2
> 41 DB 11 0D 11 F4 D0 F3 D8 01 0D 11 24 7F 30 D7
> 
> 
> 15 11 70 7C 76 6F ED 1A 3E 2F 34
> 15 11 E0 AF F7 12 A7 CB CD 17 34
> 0D 11 8C 5A F9 2F 01
> 0D 11 E0 CF 70 D9 3A
> 0F 12 68 7C CC E6 F0 00
> 0D 12 E0 1E 80 79 1F
> 11 11 D4 0B 3E 19 00 17 0C
> 0D 01 78 B2 41 DB 11
> 0D 11 F4 D0 F3 D8 01
> 
> 
> 
> In a Huffman encoded file looks RGN Section 6 much more "random".
> 
> 
> 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
> -----------------------------------------------
> F9 9F 7F F8 3E 80 98 7D FC 09 45 F0 7C E6 E4 00
> 83 FF 7C 0A C8 E5 1F 40 40 FF 41 E4 80 CF FF C6
> FF 7E C0 C9 40 F4 21 F2 FE 02 FF 33 F8 20 40 FF
> FC FF E1 21 1F 7E 06 FF FD 00 FC FF A1 8F 29 FB
> 
> According to this file TRE Section 7 it should be splitted as
> 
> F9 9F 7F F8 3E
> 80 98 7D FC 09 45 F0 7C
> E6 E4 00
> 
> 
> 
> The question is:
> Do anyone know what it might be in RGN Section 6.
> Even a bit more than what I found so far is of interest.
> Any hint in this topic is much appreciated.
> 
> Best Regards
> 
> /Thomas
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