[postgis-users] Making a Polygon from Points

[David Potts]

Thanks Jan,

Worked a treat:-)

Dave.
> Hi David,
>
> I do it like this:
>
> select geometryfromtext
> ('Polygon (('  || array_to_string
>     (array
>         (
>             (select x(crd) || ' ' || y(crd)
>                   from points
>                   order by nr
>             )
>             union all
>             (select x(crd) || ' ' || y(crd)
>                  from points
>                  order by nr
>                  limit 1
>             )
>        ),','
>     ) || '))',srid
> ) as the_geom
>
> First put the points in an array, add the first point at the last
> position, and convert the array to a GEOMETRY string. You need a column
> to orders the points (nr in this case).
>
> Jan
>
>
> David Potts wrote:
>> Hi
>>
>> I trying to make a polygon or closed linestring from a list of points.
>>
>> I can say something like
>>
>>
>>  insert into lines(the_geom) select ST_MakeLine(foo.the_geom)
>> from(select
>> the_geom from hack where generation=1 and circle=0 ) as foo;
>>
>> This results in a open line that runs through all off the points,  I am
>> trying to generate either a closed line or a polygon.
>>
>> Using functions like  ST_Polygonize, generate an empty goetry
>> collection.
>>
>> Does anybody have any suggestions on how I generate a closed linestring
>> or
>> a polygon?
>> regards
>>
>> Dave.
>>
>


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