Strangely enough, ExecuteSQL works (it returns an osgeo.ogr.layer object with
one feature) with
'select FID from judeteEPSG3844 where DENJUD = "CLUJ"'
but later a GetField('FID') request returns "Illegal field requested in
GetField()"
-marius
Date: Tue, 12 Jul 2011 11:36:42 -0400
Subject: Re: [gdal-dev] OGR Geometry methods
From: [email protected]
To: [email protected]
does executing
sql = 'select FID from judeteEPSG3844 where DENJUD = "CLUJ"'
return anything?-----
Luke Peterson
312-533-1051(m)
On Tue, Jul 12, 2011 at 11:30 AM, Marius Jigmond <[email protected]>
wrote:
Luke,
GetFIDColumn returns an empty string (not supported according to the docs). I
tried the following SQL statement:
sql = 'select DENJUD from judeteEPSG3844 where DENJUD = "CLUJ"'
but it's still returning that same wrong feature.
-marius
Date: Tue, 12 Jul 2011 09:13:00 -0400
Subject: Re: [gdal-dev] OGR Geometry methods
From: [email protected]
To: [email protected]
-----
Luke Peterson
- sent via mobile device -
On Jul 11, 2011 11:00 PM, "Marius Jigmond" <[email protected]> wrote:
>
> After some more investigation that is likely NOT the issue. I have an
> ExecuteSQL statement which selects a certain polygon based on an attribute
> value. Unfortunately it seems to return the wrong feature. The feature I
> query for is unique so a duplicate is out of the question. Here's the code:
>
> #!/usr/bin/python
>
> from osgeo import ogr
> import sys, math, time, os
>
> aquifer = '/data/romania/judeteEPSG3844.shp'
> aqDS = ogr.Open(aquifer)
> sql = 'select * from judeteEPSG3844 where DENJUD = "CLUJ"'
> aqLayer = aqDS.ExecuteSQL(sql)
> feat = aqLayer.GetFeature(0)
> print aqLayer.GetFeatureCount()
> print feat.GetField('DENJUD')
> aqDS.ReleaseResultSet(aqLayer)
>
> The result:
> marius@mobi:~/temp$ run_sql.py
> 1
> TELEORMAN
> marius@mobi:~/temp$
>
> This explains why none of my centroids were remotely close to the polygon.
>
> Is there something wrong with my query or should I file a bug?
>
Can you select the feature by its FID instead? (apologies, I'm banging this out
on my phone ... probably won't run but you should get the idea):
aqLayer = aqDS.GetLayerByIndex(0) #gets the whole shapefile
aqFID = aqLayer.GetFIDColumn() # I forget the method name here... hope this is
right but may have to pull in the layer def
sql = 'select %s from judeteEPSG3844 where DENJUD = "CLUJ"' % aqFID #
specifically asking for just the FID field in the resultset
sqlResults = aqDS.ExecuteSQL(sql) # sql results same as before
featFID = sqlResults.GetFeature(0).GetFieldAsInt(aqFID) #this should be the
actual FID of the results (problems would occur if your sql returned more than
one hit)
feat = aqLayer.GetFeature(featFID) # using the fid to grab the feature from the
0th layer in the shapefile
This may be a long way around ...
> -marius
>
>
> On Mon, 2011-07-11 at 20:46 -0500, Marius Jigmond wrote:
>>
>> I suppose a piece of code speaks louder :):
>>
>> xsect = False
>> for i in range(gridLayer.GetFeatureCount()):
>> feat = gridLayer.GetFeature(i)
>> geom = feat.GetGeometryRef()
>> point = geom.Centroid()
>> for j in range(aqLayer.GetFeatureCount()):
>> aqfeat = aqLayer.GetFeature(j)
>> aqgeom = aqfeat.GetGeometryRef()
>> if point.Intersect(aqgeom):
>> xsect = True
>> print 'ibound = 1'
>> break
>> if xsect:
>> feat.SetField('IBOUND', 1)
>> gridLayer.SetFeature(feat)
>> xsect = False
>>
>> -marius
>>
>> On Mon, 2011-07-11 at 20:34 -0500, Marius Jigmond wrote:
>>>
>>> Hi everyone,
>>>
>>> I am trying to test whether centroids of polygons lie/intersect within
>>> another polygon. I have tried Intersect, Within, and Contains but they
>>> always return false. Should these methods work for my intended purpose or
>>> do I need to implement a point in polygon function? Thanks.
>>>
>>> -marius
>>>
>>> _______________________________________________
>>> gdal-dev mailing list
>>> [email protected]
>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>> _______________________________________________
>> gdal-dev mailing list
>> [email protected]
>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
>
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