# How to identify a point is belong to a polygon ?

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## How to identify a point is belong to a polygon ?

 Hi everyone, Do you know how to identify whether a point (OGRPoint) is belong to a polygon (OGRPolygon) ? (the polygon covers the point) Thanks and regards, Tai
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## Re: How to identify a point is belong to a polygon ?

 Tai,You can use OGR_G_Within()OGR_G_WIthin(point,polygon) will return true if the point is within the polygon.You can access various other geometry functions from the OGRGeometry class.http://www.gdal.org/ogr/ogr__api_8h.html#a80ba9e516ccae381ae7240cc9684eb72 On Fri, Jul 20, 2012 at 7:04 AM, taibc wrote: Hi everyone, Do you know how to identify whether a point (OGRPoint) is belong to a polygon (OGRPolygon) ? (the polygon covers the point) Thanks and regards, Tai -- View this message in context: http://osgeo-org.1560.n6.nabble.com/How-to-identify-a-point-is-belong-to-a-polygon-tp4989501.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Best regards,Chaitanya kumar CH.+91-949444758417.2416N 80.1426E _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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## Re: How to identify a point is belong to a polygon ?

 Tai,You can use the spatial filter of the ogr layer to filter the point features to speed things up. You will still have to test if the point is within the polygon but it will be faster.Also, make sure the test is like point->Within(polygon) and not polygon->Within(point) OGRLayer::SetSpatialFilter()http://www.gdal.org/ogr/classOGRLayer.html#a0b4ab45cf97cbc470f0d60474d3e4169 On Fri, Jul 20, 2012 at 9:29 AM, Bui Chi Tai wrote: Chaitanya,I am checking my code. Maybe it is not successful because I used two different layers (of one file). As you know, one .dgn files only has one layer, that include many features, and Texts (Point Geometry), Polygons are treated as features.My idea is: First, I will read each feature to identify whether this feature is a polygon. Then, I need to use a loop to read and check all features of layer to identify whether a Text (point) is belong to that polygon. But, this will affect to the first reading times, and give unexpected result. Do you have any ideas ?Thanks and regards,Tai From: Chaitanya kumar CH <[hidden email]> To: Bui Chi Tai <[hidden email]> Sent: Friday, July 20, 2012 10:39 AM Subject: Re: [gdal-dev] How to identify a point is belong to a polygon ? Tai,I don't understand why it would happen. Can you provide some more details? Code, data?On Fri, Jul 20, 2012 at 9:05 AM, Bui Chi Tai wrote: Thanks Chaitanya, I am trying to use this method. But, it is not successful. For example: One file .dgn includes Text (treated as a point geometry) and Shapes (Polygon). I used the method OGRGeometry::Within(OGRGeometry * other) to identify whether the Text is belong to the polygon. But it doesn't return an expected result (Actually, there are some texts that belong to each polygon). Kind regards,Tai From: Chaitanya kumar CH <[hidden email]> To: taibc <[hidden email]> Cc: [hidden email] Sent: Friday, July 20, 2012 10:11 AM Subject: Re: [gdal-dev] How to identify a point is belong to a polygon ? Tai,You can use OGR_G_Within()OGR_G_WIthin(point,polygon) will return true if the point is within the polygon.You can access various other geometry functions from the OGRGeometry class.http://www.gdal.org/ogr/ogr__api_8h.html#a80ba9e516ccae381ae7240cc9684eb72 On Fri, Jul 20, 2012 at 7:04 AM, taibc wrote: Hi everyone, Do you know how to identify whether a point (OGRPoint) is belong to a polygon (OGRPolygon) ? (the polygon covers the point) Thanks and regards, Tai -- View this message in context: http://osgeo-org.1560.n6.nabble.com/How-to-identify-a-point-is-belong-to-a-polygon-tp4989501.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Best regards,Chaitanya kumar CH.+91-949444758417.2416N 80.1426E -- Best regards,Chaitanya kumar CH.+91-9494447584 17.2416N 80.1426E -- Best regards,Chaitanya kumar CH.+91-949444758417.2416N 80.1426E _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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## Re: How to identify a point is belong to a polygon ?

 Hi Chaitanya, I still can't run the method "Geometry::Within". And I got the error: "GEOS support not enable" when trying use this method. Please find the attached file for sample code.Source1.cppAbout spatial filter, you said that: we can use the spatial filter of the ogr layer to filter the point features. But, I think it is used to filter features that geometrically intersect the filter geometry. For example: if I have one polygon A feature, I can use the method "SetSpatialFilter" to get other features (Point or Polygon) that geometrically intersect with A. chaitanya_ch wrote Tai, You can use the spatial filter of the ogr layer to filter the point features to speed things up. You will still have to test if the point is within the polygon but it will be faster. Also, make sure the test is like point->Within(polygon) and not polygon->Within(point) OGRLayer::SetSpatialFilter() http://www.gdal.org/ogr/classOGRLayer.html#a0b4ab45cf97cbc470f0d60474d3e4169On Fri, Jul 20, 2012 at 9:29 AM, Bui Chi Tai <[hidden email]>wrote:
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## Re: How to identify a point is belong to a polygon ?

 Tai,GDAL needs GEOS to perform these geometry functions. Make sure you install that.On Sat, Jul 21, 2012 at 12:19 PM, taibc wrote: Hi Chaitanya, I still can't run the method "Geometry::Within". And I got the error: "GEOS support not enable" when trying use this method. Please find the attached file for sample code. http://osgeo-org.1560.n6.nabble.com/file/n4989766/Source1.cpp Source1.cpp About spatial filter, you said that: we can use the spatial filter of the ogr layer to filter the point features. But, I think it is used to filter features that geometrically intersect the filter geometry. For example: if I have one polygon A feature, I can use the method "SetSpatialFilter" to get other features (Point or Polygon) that geometrically *intersect* with A. chaitanya_ch wrote > > Tai, > > You can use the spatial filter of the ogr layer to filter the point > features to speed things up. You will still have to test if the point is > within the polygon but it will be faster. > > Also, make sure the test is like point->Within(polygon) and not > polygon->Within(point) > > OGRLayer::SetSpatialFilter() > http://www.gdal.org/ogr/classOGRLayer.html#a0b4ab45cf97cbc470f0d60474d3e4169 > > On Fri, Jul 20, 2012 at 9:29 AM, Bui Chi Tai wrote: > > -- View this message in context: http://osgeo-org.1560.n6.nabble.com/How-to-identify-a-point-is-belong-to-a-polygon-tp4989501p4989766.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Best regards,Chaitanya kumar CH.+91-949444758417.2416N 80.1426E _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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## Re: How to identify a point is belong to a polygon ?

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## Re: How to identify a point is belong to a polygon ?

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## Re: How to identify a point is belong to a polygon ?

 Thanks Chaitanya, I reported the error there. And waiting for answers. Kind regards, Tai
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## Re: How to identify a point is belong to a polygon ?

 In reply to this post by chaitanya_ch chaitanya_ch wrote Tai, GDAL needs GEOS to perform these geometry functions. Make sure you install that. On Sat, Jul 21, 2012 at 12:19 PM, taibc <[hidden email]> wrote: Hi Chaitanya, I installed GEOS succesfful, and copy file geos.dll into my project. But I still got the error: "GEOS support not enable" when using the method "Within" Are there something wrongs ? Thanks and regards, Tai
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## Re: How to identify a point is belong to a polygon ?

 On 23 July 2012 11:52, taibc <[hidden email]> wrote: > I installed GEOS succesfful, and copy file geos.dll into my project. But I > still got the error: "GEOS support not enable" when using the method > "Within" > > Are there something wrongs ? You need to edit nmake.opt and rebuild GDAL. Check this thread: http://lists.osgeo.org/pipermail/gdal-dev/2010-March/023829.htmlBest regards, -- Mateusz Loskot, http://mateusz.loskot.net_______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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 Thanks Mateusz,I edited the nmake.opt by adding below lines:GEOS_DIR = C:/geos-3.3.5GEOS_LIB = $(GEOS_DIR)/src/geos_c_i.libGEOS_CFLAGS = -I$(GEOS_DIR)/capi -I$(GEOS_DIR)/include/geos -DHAVE_GEOSThen, I rebuilt GDAL, but still got the error: "GEOS support not enable".Kind regards,Tai From: Mateusz Loskot [via OSGeo.org] <[hidden email]> To: taibc <[hidden email]> Sent: Monday, July 23, 2012 5:56 PM Subject: Re: How to identify a point is belong to a polygon ? On 23 July 2012 11:52, taibc <[hidden email]> wrote: > I installed GEOS succesfful, and copy file geos.dll into my project. But I > still got the error: "GEOS support not enable" when using the method > "Within" > > Are there something wrongs ? You need to edit nmake.opt and rebuild GDAL. Check this thread: http://lists.osgeo.org/pipermail/gdal-dev/2010-March/023829.htmlBest regards, -- Mateusz Loskot, http://mateusz.loskot.net_______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev If you reply to this email, your message will be added to the discussion below: http://osgeo-org.1560.n6.nabble.com/How-to-identify-a-point-is-belong-to-a-polygon-tp4989501p4990029.html To unsubscribe from How to identify a point is belong to a polygon ?, click here. NAML Reply | Threaded Open this post in threaded view | ## Re: How to identify a point is belong to a polygon ?  Tai,If your rebuild was successful with geos, the only reason for you to get the error is that the application is accessing the wrong libraries somewhere in your system. Do a clean rebuild and make sure the LD_LIBRARY_PATH and GDAL_DATA are set correctly. On Tue, Jul 24, 2012 at 7:37 AM, taibc wrote: Thanks Mateusz,I edited the nmake.opt by adding below lines: GEOS_DIR = C:/geos-3.3.5GEOS_LIB =$(GEOS_DIR)/src/geos_c_i.libGEOS_CFLAGS = -I$(GEOS_DIR)/capi -I$(GEOS_DIR)/include/geos -DHAVE_GEOS Then, I rebuilt GDAL, but still got the error: "GEOS support not enable".Kind regards,Tai From: Mateusz Loskot [via OSGeo.org] <[hidden email]> To: taibc <[hidden email]> Sent: Monday, July 23, 2012 5:56 PM Subject: Re: How to identify a point is belong to a polygon ? On 23 July 2012 11:52, taibc <[hidden email]> wrote: > I installed GEOS succesfful, and copy file geos.dll into my project. But I > still got the error: "GEOS support not enable" when using the method > "Within" > > Are there something wrongs ? You need to edit nmake.opt and rebuild GDAL. Check this thread: http://lists.osgeo.org/pipermail/gdal-dev/2010-March/023829.htmlBest regards, -- Mateusz Loskot, http://mateusz.loskot.net_______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev If you reply to this email, your message will be added to the discussion below: http://osgeo-org.1560.n6.nabble.com/How-to-identify-a-point-is-belong-to-a-polygon-tp4989501p4990029.html To unsubscribe from How to identify a point is belong to a polygon ?, click here. NAML View this message in context: Re: How to identify a point is belong to a polygon ? Sent from the GDAL - Dev mailing list archive at Nabble.com._______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev-- Best regards,Chaitanya kumar CH. +91-949444758417.2416N 80.1426E _______________________________________________ gdal-dev mailing list [hidden email] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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