[postgis-users] Path to closest neighbor

[Nalin C]

Ya, it's near the southern tip of India, a point in Sri Lanka. x, y has been
given correct. I used 4326 as the SRID. 



Stephen Woodbridge wrote:
> 
> You need to read up on pgRouting and probably join the pgRouting list
> 
> http://pgrouting.postlbs.org/
> http://lists.postlbs.org/mailman/listinfo/pgrouting-users
> 
> -Steve
> 
> Nalin C wrote:
>> Also, can you please suggest me the functions that can be used for points
>> 2
>> and 3 ?  I'm totally a newbie to postgis. 
>> 
>> In point 2, it would be great if the path can start from in front of the
>> hospital, instead a vertex in roads table.
>> 
>> 
>> 
>> Nalin C wrote:
>>> Hi Steve,
>>>
>>> Thank you for the quick reply.
>>>
>>> I observed that the results returned by :
>>>
>>> select name, the_geom from hospitals order by
>>> distance_sphere(setsrid(makepoint(79.877778, 6.914722), 4326), the_geom)
>>> asc limit 3; 
>>>
>>> are not the closest hospitals to the given accident point. I'm not sure
>>> what has gone wrong.
>>>
>>>
>>> Thanks,
>>>
>>> Nalin
>>>
>>>
>>>
>>> Stephen Woodbridge wrote:
>>>> Nalin C wrote:
>>>>> Hi,
>>>>>
>>>>> I have two tables for roads and hospitals. I'm looking for suitable
>>>>> pgrouting function(s) for following scenario.
>>>>>
>>>>> Given the accident point (in point geometry), finding the least
>>>>> distant
>>>>> hospital and draw the path.
>>>>>
>>>>> Following functionality is needed.
>>>>>
>>>>> 1. One end of the drawn path needs to start from in front of the
>>>>> closest
>>>>> hospital (which is in hospitals table).
>>>>> 2. Path needs to stop from the accident point on road.
>>>>>
>>>>> I'm new to pgrouting and appreciate your help.
>>>> You have a few discrete tasks. Assuming you have the location of the 
>>>> accident:
>>>>
>>>> 1) Select say the three closest hospitals based on straight line 
>>>> distance. (x,y) is the location of the accident.
>>>>
>>>> select name, the_geom from hospitals where order by 
>>>> distance_sphere(setsrid(makepoint(x,y), 4326), the_geom) asc limit 3;
>>>>
>>>> 2) then use pgRouting to use the Hospital location as start and the 
>>>> accident as end and comput the routes
>>>>
>>>> 3) compare the routed distances and select the shortest.
>>>>
>>>> -Steve W
>>>> _______________________________________________
>>>> postgis-users mailing list
>>>> postgis-users at postgis.refractions.net
>>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
>>>>
>>>>
>>>
>> 
> 
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