Well,
I found many proposed solutions to my problem and just to let you all
know,the concept I was asking for is : "Concave hull".
Google search for it !
On Wed, May 5, 2010 at 5:28 PM, Oscar Zamudio wrote:
> Now that I get this polygon I found that it encloses all the streets in my
> table and
Now that I get this polygon I found that it encloses all the streets in my
table and follows some more or less smooth path around them, much better
than a bounding box. Butto be honest, it is not the best suitable for my
purposes. I want a footprint of the whole bunch of streets. I mean: suppos
> Nicolas,
> What I want to do is an insert of the type INSERT INTO...VALUES .. as
> follows:
>
> INSERT INTO boundaries ( the_geom, the_name ) VALUES
> (some_geometry_data,'some_arbitrary_name')
>
> My problem is that I want to replace the some_geometry_data value by the
> result of the SELECT qu
Nicolas,
What I want to do is an insert of the type INSERT INTO...VALUES .. as
follows:
INSERT INTO boundaries ( the_geom, the_name ) VALUES
(some_geometry_data,'some_arbitrary_name')
My problem is that I want to replace the some_geometry_data value by the
result of the SELECT query. And of cou
On 5 May 2010 02:38, Oscar Zamudio wrote:
> Well, it works like a charm!
> But I still need some advise. The query generates a polygon and I use astext
> to get readable output. Now I create a new table that will contain a name
> and the geometry result of the query. I want to use something like:
Well, it works like a charm!
But I still need some advise. The query generates a polygon and I use astext
to get readable output. Now I create a new table that will contain a name
and the geometry result of the query. I want to use something like:
INSERT INTO boundaries ( the_geom, the_name ) VALU
I must to recognize that today I did not research further about that, I just
remember something about convex hull from my scientific research background.
Anyway in my case if the convex hull of the streets table doesn't work in
the straight manner, I still can make a new table containing first and
I believe that the convex hull of a set of lines is the same as the
convex hull of the vertices of the lines. So it should do what you want.
But if you have a reference showing otherwise I'd be interested to see it.
Oscar Zamudio wrote:
ha, ha!!,
My knowledge come from Maths ,and certainly
ha, ha!!,
My knowledge come from Maths ,and certainly not from Postgis!. The concept
of Convex Hull (in algorithms and math fields) is always applied to set of
points and I remember there was a big challenge to find a good method for
lines (some years ago). But I don't mind Math anymore, if this fu
On Mon, May 03, 2010 at 11:18:03AM -0300, Oscar Zamudio wrote:
> Thanks strk,
> As far as I know convex hull basically applies to a collection of points...,
> nevertheless, I will try with my set of lines.
How far does your knowledge come from ? :)
http://postgis.refractions.net/docs/ST_ConvexHull
Thanks strk,
As far as I know convex hull basically applies to a collection of points...,
nevertheless, I will try with my set of lines.
On Mon, May 3, 2010 at 9:56 AM, strk wrote:
> On Mon, May 03, 2010 at 09:32:54AM -0300, Oscar Zamudio wrote:
> > I need to clarify: my table is a table of str
On Mon, May 03, 2010 at 09:32:54AM -0300, Oscar Zamudio wrote:
> I need to clarify: my table is a table of streets. So ... I don't know how
> to proceed.
You may be looking for ST_ConvexHull. Something like:
SELECT ST_ConvexHull(ST_Collect(the_geom)) from mytable;
--strk;
() Free GIS & Flas
I need to clarify: my table is a table of streets. So ... I don't know how
to proceed.
On Mon, May 3, 2010 at 9:30 AM, George Silva wrote:
> From what i understood of your request, you need to collect all the
> polygons and merge in a single one. Use the St_Collect function to do that.
>
> The b
>From what i understood of your request, you need to collect all the polygons
and merge in a single one. Use the St_Collect function to do that.
The bounding box function will give you the extent of the whole, as you
described. This is default behavior.
Att
On Mon, May 3, 2010 at 9:28 AM, Oscar
Hi all,
I'm using the extent function to get the geographic coverage of a table.
That function returns a bounding box, i.e. a polygon with 4 points (XMin
YMin ...etc). I do know that the actual coverage of teh table is not a four
points polygon but an arbitrary polygonal shape with many vertexs. I
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