[mkgmap-dev] next steps in routing

Mon Dec 1 16:04:53 GMT 2008

Hi,

On 11/30/08, Robert Vollmert <rvollmert-lists at gmx.net> wrote:
> Hi,
>
> what are your thoughts on what to look at next regarding routing?
>
> Considering that my small sample maps now route fine, is it time to go
> towards bigger routable maps?NOD 1 with multiple RouteCenters, in
> particular, is something I'd like to give, but I wouldn't want to duplicate
> work.

Several things on routing.
- Blocks are alligned in 4096 bytes.
- The bitmap len at the end of road in NET is the count of nodes in
the road, for every node there is 1 bit in the bitmap.
I've seen bitmaps with holes, not all bits ones. But don't
know yet what they mean.
The so called extra bit:
marks a node in the graph.

Road with just one node:
| R2
|
X----------- where X is in R1 have bmlen=1 and no extra bit.
|      R1
|

Also X is the first point in the line.

Road with two nodes:
| R2         |
|               |
X----------X
|     R1     |
|               |

Here R1 have no extra bit too, and a bmlen=2.

In both cases they have only one segment in net.
Longer roads:
seg1, seg2, seg3, seg4, .... in NET that are referencing graphical
data in TRE/RGN.
      seg1                         seg2                         seg3
                   seg4
X-------X-----------  ----------X----------------X
----------------------- --------X------X
In seg1 first point is always a node, so extra bit is not set.
in seg2 first is not set too, if there is a node the last point in seg1 is set.
Coordinates of last from seg1 and first from seg2 are equal, same for
other segXs.
So seg1 and seg2 have total of 4 nodes.
seg3 have no nodes,
seg4 have 2 nodes.
So the road have total  6 nodes on 4 segments
bmlen=6 and the bitmap 111111.

-- 
have fun,
alex