[postgis-users] Pgrouting directions

[Ahmad Bdair]

Yes, that is something very similar to what I need to do, I already wrote a
php code to check angels and slopes, but it was not accurate, it was more
life "if else" code, I check the longlat for current segment with longlat
for the previous one, I guess you didn't use the database for direction
calculation(except for routing) am I right? Isn't steps 3 and 4 depends on
your angel calculations?

I have the roads with two different languages, a road map like anyother road
map I guess.

On Tue, Dec 30, 2008 at 3:17 AM, Stephen Woodbridge <woodbri at swoodbridge.com
> wrote:

> bdair2002 wrote:
>
>> Hello,
>> I am developing an application using Pgrouting with Postgis data,
>> everything
>> is fine, but now I am looking  to do something like Google directions
>> guide,
>> where it tells you turn left or right, I am wondering if this feature is a
>> built-in feature in Pgrouting or Postgis.
>>
>> Regards
>>
>
> No this is not a feature that is part of either.
>
> I have implemented a directions explicator, but it is somewhat specific to
> the data that you have, as you need to know what column(s) contain the road
> names, if you have signage information then you need to know how to link to
> that. If you want to be able to explicate in multiple languages, then you
> probably need to consider supporting multiple languages each in a separate
> table the you can select from when you generate the languages.
>
> The algorithm is pretty straight forward as the you currently get a list of
> segments that make up the route. Then you need to:
>
> analyze each segment and
> 1) check to see if you want to join it with the previous segment because
> the road name matches
> 2) check the angle that it makes with the last segment to determine right,
> left, straightness of turn
> 3) compute the compass heading for the segment
> 4) determine if you have signage
> 5) based on these, determine if you are read to explicate and which
> predefined instruction you need to explicate an instruction
> 6) loop through all segments
>
> For a demo of this you can try:
> http://imaptools.com/leaddog/routing/dd.html
>
> Zoom into a city in one of the yellow areas, set a start and end point and
> click [calculate route] button. The driving directions should show below the
> button if it was successful, be patience the routing is running on a 333MHz
> box.
>
> -Steve
>
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