[RouterGeocoder] Poly line features

[Stephen Woodbridge]

Hello Roni,

Ashraf Hossain wrote:
> We can make a graph builder which will create 3 things.
> 
> 1. Connectivity information for polylines.
>     It will contain the the vertex numbers for each polyline feature.
> 
> 2. Graph file for the whole polyline layer.
>      Vertex edge collection.
> 
> 3. Weight matrix for the graph.
> 
> 
> Primarily this can be created from the shape file and the dbf(may be
> there contain a minimization parameter information like
> routingtime,secured road,cost ...etc.)file. Later it will support all
> kind of format.

Yes, this all sounds good. The other missing piece you might want to 
consider adding and supporting is turn restrictions.

While this data can all be generated from shapefile data and data in 
other formats, the data required for routing is usually in a different 
format to be efficient during the routing phase. Therefore it might make 
sense to define these data structures a schema that can then be mapped 
to data structures in an implementation language. This would make for a 
more modular approach that would allow us to decouple the structure from 
the physical storage and make the code more modular and reusable.

> There will be a routing layer in the mapserver which will read the
> information from this files and then can draw the shortest paths.

While this would be an interesting possibility, have a generic routing 
engine as a library, would allow us to plug it into mapserver, or any 
number of other applications. Basically mapserver only needs the 
resulting polyline and their are lots of ways we could pass that to 
mapserver.

> There will be a text driving direction generator class which can be
> showed in the client side.

Correct, In fact if you are using OpenLayers as a client, then a simple 
Ajax call from the client to generate the route can return the route and 
the driving directions in XML for display. Here is a demo I put together 
using pgRouting with some of my own mods:

http://imaptools.com/leaddog/routing/dd.html

To use it zoom into one of the citys, or click one of the city links on 
the left then select a start and end and display the route and 
directions. If you use FireFox and FireBug you can see the requests and 
responses. Sometimes it fails to route so change the start and ends 
until it does.

> And finally there will be another request for the navigation client support.
> 
> 
> From the index tree of the polyline it will select the source
> feature(like feature info ) and same for the destination.
> 
> We then can use the shortest path algorithm for generating the shortest path.

Yes, this is exactly what I do in the demo linked above.

> Please help me if I done any mistake.
> 
> 
> In the second or third phase I want to add the Bus and car hybrid
> routing(google already implemented this).

There are lots of additional feature that can be added. If you have data 
for public transit systems and walkways then you can do route planning 
for pedestrians also.

Best regards,
   -Steve

> With Regards
> Roni