[postgis-users] RE: RE: RE: Select Point or PolyGon Polyline in Box

Fri Apr 13 10:05:20 PDT 2007

Anhtin,

Sorry I misunderstood what you were trying to do.  I guess your mainroads are just regular old lines and not boundary lines of polygons.  The buildarea is meant to take a closed line and convert to a polygon. If its not closed I think it just returns null.

 I think what you want then if you are trying to find what road a point sits on is 

SELECT * FROM mainroad WHERE GeomFromText('POINT(517651 2121421)', 42102) &&
the_geom 
 AND distance(the_geom,
GeomFromText('POINT(517651 2121421)', 42102)) = 0

 - and for that you don't need build area

If you are dealing with centerlines - you may however need to expand your line out a bit and check if a point sits within x distance of a line if your points aren't exactly aligned on road centerlines.  Something like

SELECT * FROM mainroad WHERE expand(GeomFromText('POINT(517651 2121421)', 42102),1) &&
the_geom
 AND distance(the_geom,
GeomFromText('POINT(517651 2121421)', 42102)) <= 1

where 1 you can replace with whatever you think is a good measure for a width of a road.

Hope that helps,
Regina

________________________________

From: postgis-users-bounces at postgis.refractions.net on behalf of anhtin
Sent: Thu 4/12/2007 10:39 PM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] RE: RE: RE: Select Point or PolyGon Polyline in Box

thanks very much all support to me :)
i still understand in Select point with PolyLine with command :
when i run
SELECT * FROM mainroad WHERE GeomFromText('POINT(517651 2121421)', 42102) &&
the_geom
Have some result

if have assgin to add the command:

 AND distance(BuildArea(the_geom),
GeomFromText('POINT(517651 2121421)', 42102)) = 0

but it no result ????? i dont understand this command

Obe, Regina     DND\MIS wrote:
>
> To find the polygon where a point resides - there are actually several
> ways of doing this and I'm not sure which one is fastest or the
> preferred. There is (in these I am assuming the_poly is the polygon
> geometry)
>
> I usually just do the first because it is pretty all purpose for most of
> the things I do and you don't have to think about the order of arguments
> in distance like you have to in within)
>
> SELECT *
> FROM polygon WHERE GeomFromText('POINT(295149 2315499)', -1) && the_poly
> AND distance(the_poly, GeomFromText('POINT(295149 2315499)', -1)) = 0
>
> There is also
>
> SELECT *
> FROM polygon WHERE GeomFromText('POINT(295149 2315499)', -1) && the_poly
> AND Within(GeomFromText('POINT(295149 2315499)', -1),the_poly)
>
>
> For Poly Line's it's a little trickier because there is no such thing in
> postgis lingo for Polyline.  I think the closest is Linestring or
> MultiLineString. So if you have a linestring or multilinestring that
> forms a polyline, I'm not sure if you would have to convert it to a
> polygon using buildarea to get what you want or if you can get away with
> some other relational operator to do it without conversion.  NOTE:  I
> have never tried this before - this is simply a guess on my part
>
> the_polyline is a linestring or multilinestring.
>
>
> SELECT *
> FROM polylines WHERE GeomFromText('POINT(295149 2315499)', -1) &&
> the_polyline AND distance(BuildArea(the_polyline),
> GeomFromText('POINT(295149 2315499)', -1)) = 0
>
> OR
>
> SELECT *
> FROM polylines WHERE GeomFromText('POINT(295149 2315499)', -1) &&
> the_polyline AND Within(GeomFromText('POINT(295149 2315499)',
> -1),BuildArea(the_polyline))
>
>
>
>
>
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
> anhtin
> Sent: Wednesday, April 11, 2007 11:40 PM
> To: postgis-users at postgis.refractions.net
> Subject: [postgis-users] RE: RE: Select Point or PolyGon Polyline in Box
>
>
> Thanks very much  so support for me
>
> if  i have that point i want select this point be in Polygon
> ex: i have table Polygon is province.  i want select point(295054
> 849444) be
> in Polygon  ????
> and or be in polyline
> can u show 2 way with polygon and polyline
> thanks befor :)
>
>
>
> Obe, Regina     DND\MIS wrote:
>>
>> Don't quite get what you are asking?  Are you trying to compare if 2
>> points are the same or if a point is within x distance of another
> point?
>> or something entirely different?
>>
>> If you wanted to select all points within x distance of your reference
>> point , then it would be (again replace -1 with the correct SRID and
>> distance is always measured in the units of your spatial reference
>> system)
>>
>> SELECT *
>> FROM pointdemo
>> WHERE the_point && Expand(GeomFromText('POINT(295149 2315499)', -1),
> 10)
>> AND
>>      distance(the_point,GeomFromText('POINT(295149 2315499)', -1)) <=
>> 10
>>
>> If you wanted to know if 2 points are the same then it would be
>> SELECT *
>> FROM pointdemo
>> WHERE the_point ~= GeomFromText('POINT(295149 2315499)', -1)
>>   
>>
>> 
>>
>> -----Original Message-----
>> From: postgis-users-bounces at postgis.refractions.net
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
>> anhtin
>> Sent: Wednesday, April 11, 2007 12:32 AM
>> To: postgis-users at postgis.refractions.net
>> Subject: [postgis-users] RE: Select Point or PolyGon Polyline in Box
>>
>>
>> thanks
>> How is Select if it is Point ?????
>>
>>
>>
>> Obe, Regina     DND\MIS wrote:
>>>
>>> Assuming your box is in the same srid as your points.  It would be
>>> something like
>>>
>>> SELECT *
>>> FROM pointdemo
>>> WHERE  the_point && setsrid('BOX(295149 2315499, 465992
>>> 2163790)'::box2d, -1)
>>>
>>>
>>> Note - above I am assuming your point geometry is called the_point
> and
>>> your SRID is -1
>>> If the srid of your point geometry is not -1 then change  -1 to what
>> it
>>> should be.
>>>
>>>
>>> -----Original Message-----
>>> From: postgis-users-bounces at postgis.refractions.net
>>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
>>> anhtin
>>> Sent: Tuesday, April 10, 2007 6:18 AM
>>> To: postgis-users at postgis.refractions.net
>>> Subject: [postgis-users] Select Point or PolyGon Polyline in Box
>>>
>>>
>>> hi all
>>> i have question to postgis
>>> i have table Pointdemo
>>> I want select all point in my Box("Rectangle") on PostGis
>>> my box is corrdinate
>>> ex: full extend is:Box(110638 2587481, 903350 1972446) ---> xmin
> ymin,
>>> xmax
>>> ymax
>>> i want select point in Box(295149 2315499, 465992 2163790)  ---> xmin
>>> ymin,
>>> xmax ymax
>>> How will i do that ?????
>>>
>>>
>>> --
>>> View this message in context:
>>>
>>
> http://www.nabble.com/Select-Point-or-PolyGon-Polyline-in-Box-tf3552167.
>>> html#a9916986
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>>>
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>>
>> --
>> View this message in context:
>>
> http://www.nabble.com/Select-Point-or-PolyGon-Polyline-in-Box-tf3552167.
>> html#a9933066
>> Sent from the PostGIS - User mailing list archive at Nabble.com.
>>
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>
> --
> View this message in context:
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> html#a9952489
> Sent from the PostGIS - User mailing list archive at Nabble.com.
>
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