[pgrouting-users] Working with Driving Distance

[Daniel Kastl]

Hi Roger,

You're using the "core" function, I think.
You could use the driving_distance wrapper function, which will return you a
polyogon.
For that you need to load this SQL:
https://github.com/pgRouting/pgrouting/blob/master/extra/driving_distance/sql/routing_dd_wrappers.sql
You can also find it in the directory where the other pgRouting SQL files
are.

The function will take these parameters then:

driving_distance(table_name varchar, x double precision, y double precision,
        distance double precision, cost varchar, reverse_cost varchar,
directed boolean, has_reverse_cost boolean)

X,Y are the coordinates you take as a center point.
You can take the returned polygon then and do other spatial queries.

Best regards,
Daniel



2010/12/22 Roger André <randre at gmail.com>

> Hi All,
>
> I need to generate some maps that show all of the road segments that are
> within a certain distance of specific points.  I have been able to generate
> some answers using the driving_distance function, but am not sure what to do
> with them.  Here's what I get:
>
> # SELECT * FROM driving_distance('SELECT gid AS id, source, target,
> length::double precision AS cost FROM edges',49,2000,false,false);
>  vertex_id | edge_id |       cost
> -----------+---------+------------------
>         15 |       9 | 1854.34547361565
>         20 |     104 | 1549.85630678904
>         22 |      68 | 858.367668935802
>         23 |     125 | 1466.02479201359
>         24 |      75 | 801.137871846872
>         25 |     125 | 1169.02817170106
>         26 |     106 | 1296.98197602289
>         48 |      71 | 902.595810873304
>         49 |     106 |                0
>         51 |      74 | 1948.07551810288
>         52 |      75 | 1620.93404864578
> (11 rows)
>
> These answers seem legit, but I'm not sure what to do with them.
> Ultimately, I need to show both the minimum enclosing polygon that
> "surrounds" all of the road segments, as well as the road segments
> themselves.  Can someone please give me some pointers as to what I can do to
> accomplish this?
>
> Thanks,
>
> Roger
> --
>
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>


-- 
Georepublic UG & Georepublic Japan
eMail: daniel.kastl at georepublic.de
Web: http://georepublic.de
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