AW: AW: Re: Fwd: [Qgis-user] QGIS "Near"
Ziegler Stefan
Stefan.Ziegler at bd.so.ch
Wed Oct 27 22:48:35 PDT 2010
Hi Giuseppe
thanks for looking into this. Do you think it's worth filling out a bug report since the nearestNeighbor method does not the keep the promise or is this the normal behaviour of a spatial index based method?
regards
Stefan
mit freundlichem Gruss
Stefan Ziegler
----- Originalnachricht -----
Von: "Giuseppe Sucameli" <sucameli at faunalia.it>
Gesendet: Mit, 27.10.2010 17:30
An: "Ziegler Stefan" <Stefan.Ziegler at bd.so.ch>
Cc: "Jim Hammack" <hammack at gotslack.org> ; qgis-user <qgis-user at lists.osgeo.org>
Betreff: Re: AW: Re: Fwd: [Qgis-user] QGIS "Near"
Hi Stefan,
your workaround works fine in my case!
I looked at the QgsSpatialIndex code and I have bad news... It uses the bounding box
of the geometries!
This means that your workaround can work in a lot of cases but not in all cases, e.g. if
you have more than N geometries (10 considering your workaround), ones inside
each other.
Cheers.
On Tue, Oct 26, 2010 at 6:47 PM, Ziegler Stefan <Stefan.Ziegler at bd.so.ch> wrote:
Hi Giuseppe
I wrote a little workaround. Could you please update to 0.0.6 and check it with your test case? Thanks.
regards
Stefan
mit freundlichem Gruss
Stefan Ziegler
----- Originalnachricht -----
Von: "Giuseppe Sucameli" <sucameli at faunalia.it>
Gesendet: Mon, 25.10.2010 14:09
An: "Ziegler Stefan" <Stefan.Ziegler at bd.so.ch>
Cc: "Jim Hammack" <hammack at gotslack.org> ; qgis-user <qgis-user at lists.osgeo.org>
Betreff: Re: AW: Re: Fwd: [Qgis-user] QGIS "Near"
Hi all,
two days ago I wrote a similar plugin for a LD talk in Pisa.
I was unaware of the QgsSpatialIndex class (seems there's no documentation
about it in the online QGis API pages or maybe I missed it) so I wrote a simple
loop to find the closest feature.
Now I tried also the Nearest plugin and they are different behavior!
See the scheenshots [1] [2].
AFAICS, Nearest select a wrong polygon.
I see the plugin's code and I think it could a QgsSpatialIndex bug, but it could be
also the normal behaviour (I didn't found its documentation on the API pages
so I don't know).
I'm going to add my plugin (ClosestFeatureFinded) to the Faunalia repo so you
can try it and check the different behavior.
I hope this can help to find the bug (if any).
If you confirm it, I'll fill a bug report.
Cheers.
[1] http://img87.imageshack.us/img87/3232/nearest.jpg
[2] http://img64.imageshack.us/img64/2066/closest.jpg
On Fri, Oct 22, 2010 at 9:19 AM, Ziegler Stefan <Stefan.Ziegler at bd.so.ch> wrote:
there is some strange behaviour when using it with polygon features (at least I think it's a bit strange): sometimes when you click into a polygon I would expect that it selects the polygon I clicked into but it selects an adjacent polygon. This is probably due to the nearestNeighbor method of the spatial index. Since the two neighboring polygons share a common border the distance would be equal but the spatial index does not check if the coordindates of the mouse click lies within one of the two polygons.
regards
Stefan
mit freundlichem Gruss
Stefan Ziegler
----- Originalnachricht -----
Von: "Jim Hammack" <hammack at GotSlack.org>
Gesendet: Don, 21.10.2010 19:20
An: "Ziegler Stefan" <Stefan.Ziegler at bd.so.ch>
Cc: qgis-user <qgis-user at lists.osgeo.org>
Betreff: Re: AW: Re: Fwd: [Qgis-user] QGIS "Near"
Stefan,
I was looking for the same functionality as Zoran so have
also been working with your "Nearest" plugin. It is exactly
what I need and seems to work well.
Thanks!
Jim
On 10/20/2010 01:54 PM, Ziegler Stefan wrote:
Hi Zoran
I had some time left, took all
my code snippets and also the one from Carson. Please try
the plugin "Nearest" that should cover your example 1:
http://www.catais.org/qgis/plugins.xml
regards
Stefan
-----Ursprüngliche
Nachricht-----
Von: Zoran Jankovic [mailto:zoran.jankovic at zisis.hr]
Gesendet am: Mittwoch, 20. Oktober 2010 19:21
An: qgis-user
Betreff: Re: Fwd: [Qgis-user] QGIS "Near"
Hi Joe,
On Wed, Oct 20, 2010 at 5:06 PM, Joe
Larson <joelarso at gmail.com>
wrote:
Does the function 'snapWithContext'
http://doc.qgis.org/head/classQgsVectorLayer.html#733b974dce13d587e05cf3d4fc24f208
which "Snaps to segment or vertex within given tolerance."
seem like
what you're looking for? I came across it while trying to
get Quantum
Navigator working recently...seemed relative, but I'm no
expert!
This is similar to the mentioned solution with
selecting by radius, or changing the tolerance of ID tool.
Close, but no cigar. Since this is not very urgent, I've
decided to continue pursuing that outlined solution Carson
gave, and write a plugin i Python based on that. Since I
actually never used Python before, it may take a while,
but hey, I get to learn sth. new :-).
I never got the word back from Carson, has he developed
anything along these lines, but I have to presume he
didn't...
Anyone interested in joning me, or even earning some
money, is still invited to jump on board. My GIS
implementation project is well on the way, and it seems
there'll even be some money involved :-).
Zoran
~joe
On Tue, Oct 19, 2010 at 9:55 AM, Andreas Neumann
<a.neumann at carto.net>wrote:
> Hi Zoran,
>
> I believe the infrastructure of what you want is
already wihtin the
> selection and identify tools in QGIS. Isn't this
almost implemented in the
> current identify tool?
>
>
It sort of is, but not completely. Identify will ID
all the features within
certain radios (percentage of extent), but it will ID
_all_ of the features
within this radius. I only need the nearest, no matter
how far away... Let
us say it is, for simplicity, within current extent.
> The current identify tool selects "near" or
"close by" features within a
> certain tolerance. This tolerance can be set in
"Options" --> "Map tools"
> "search radius". I believe it currently only
effects the identify tool. Do
> you want the same tolerance also be used for the
click-selection tool?
>
>
Look above. This could be useful, but it is not the
functionality I'm
currently looking after.
> Are you also aware that in QGIS 1.6 there are new
selection tools?
>
> * by click
> * by rectangle
> * by polygon
> * by freehand
> * by radius
>
>
Yup, these are great, but they all select _multiple_
features within radius,
rectangle, etc.
> Maybe this also helps to address your needs?
>
> Of course you can combine it with previous
selections by pressing the ctrl
> key.
>
>
BR,
---
Zoran Jankovic
ZIS-Izrada softvera i savjetovanje / ZIS - Software
Development and
Consulting
http://www.zisis.hr
M: 00 385 98 682 902
T: 00 385 44 683 374
A. Senoe 4
44320 Kutina
Croatia
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