[postgis-users] RE: RE: RE: RE: Select Point or PolyGon Polyline in Box
anhtin
anhtin at gmail.com
Sun Apr 15 19:51:29 PDT 2007
thanks very much :)
u dont know help me very much.
I hope next time u will continue hepl me more :)
happy to u.
Obe, Regina DND\MIS wrote:
>
> 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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>>>
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>
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