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

From thomas at ankarsvik.nu thomas at ankarsvik.nu on Fri Mar 24 10:35:38 GMT 2023

Hi Ticker,

To much to do with to little time to spend.

I can't find anything that gives a hint of the extra byte in some TRE S7 
TRE-S7 are offset columns

UInt32  | UInt32 |UInt32 | Byte      | UInt32 columns
Polygon | Line   | Point | Flag byte | Col1 | Col2 | Coln

The smallest map you can produce is one area, like a lake, or other 
That gives Polygon- and Col1- column mandatory.
Line, Points, Flag byte are all optional with respect to small maps.

In well known sources like GPXSee, RGNDisplay and similar,
all of them skip the bytes (of my interest).
We know how to skip the extra bytes.

The amount of extra columns follow map-size and complexity.

Smallest map you can produce have 9 bytes per row. (What I have seen.)

Polygon | Flag Byte | Col1

If we focus on Col1 .. Coln
They are incremental by column.

Example with 3 rows and 3 columns:
Last row contain "Section sizes", 0x0048 is the size of RGN Section 6.
0x0000 | 0x0002 | 0x0015
0x0001 | 0x0008 | 0x0018
0x0001 | 0x0013 | 0x0032
0x0001 | 0x0013 | 0x0048

Sorry for any mis-postings done.



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