[postgis-users] Nearest Neighbour on a polygon gemeotry to a given point

[David Potts]

hi

Thank you, I will have a play with this.


> Dave,
>
> You can turn your polygon into a line that is the boundary and then use
> the
> linear referencing functions to return the nearest point along that line
> to
> your input point.
>
> select
>   st_line_interpolate_point(
>     st_exteriorring(polygongeometry),
>     st_line_locate_point(
>        st_exteriorring(polygongeometry),
>        pointgeometry
>     )
>   )
>
> David
>
> On Tue, Sep 7, 2010 at 6:55 AM, David Potts <dave.potts at pinan.co.uk>
> wrote:
>
>>
>> I have a series of x/y values that represent towns and a coastline that
>> that is encoded as a Polygon.
>>
>> I want to return the nearest point on the polygon to a town.  I have
>> seen
>> the item
>>
>> http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgis_nearest_neighbor_generic
>>
>> Which seems to be fine if you both objects that your are searching  are
>> point data or have a centroid of some type.
>>
>> What is the best solution, turn my coastal outline polygon in to a
>> series
>> of x/y values and use the solution from
>> postgis_nearest_neighbor_generic,
>> or is there some better way?
>>
>> regards
>>
>>
>> Dave.
>>
>> --
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>> except where the sender specifically states them to be the views of the
>> Pinan Software
>>
>>
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>
>
>
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> ************************************
> David William Bitner
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