[mkgmap-dev] nodes on boundary

Thu Mar 25 09:42:15 GMT 2010

Quoting Carsten Schwede <computerteddy at gmx.de>:

> Hi there,
>
> last I have read here on the mailing list about the tag for routing over
> the tile boundary. <tag k='mkgmap:on-boundary' v='1' />
>
> Since we dont use splitter for cutting the planet my question is on
> which nodes must this tag be?
>
> A sample:
>
> Tile1 #  Tile2
>        #       C
>        #       |
> A-----#-------B
>        #       |
>        #       |
>        #       D
>
>
> # tile boundary
>
> Our cutting creates the tiles so, that node A and the way between A and
> B i in the Tile 1. The nodes B, C, D and the way between them are in the
> Tile 2. Must the node B have the special on-boundary tag in both tiles,
> or only in the tile 1?
>

This is what I have understood.

Before splitting the nodes are like this

                C
                |
  A-------------B
                |
                |
                D

After splitting the nodes are like this
with a new node S inserted into A-B.

  Tile1 #  Tile2
        #
        #       C
        #       |
  A-----S-------B
        #       |
        #       |
        #       D

The node S must appear in both tiles and be flagged as a boundary node  
in both for routing to work.

In gpsmapedit you have external nodes that allow routing across  
different img files. The external nodes do not have to be on the tile  
boundary they could be international border crossing points. I am  
hoping the new boundary tags work like this.

You are unlikely to need to use this tag unless you are splitting your  
maps using some external tool because - as I understand it - if you  
use splitter then mkgmap trims the routes correctly. I plan to try  
splitting using gpsmapedit.

Garvan