MapScript Documentation (Re: [Mapserver-users] Re: problem getting bounds of poly shape)

[Puneet Kishor]

Hi Lowell,

Thanks for you reply.

> -----Original Message-----
> From: Lowell Filak [mailto:lfilak at medinaco.org] 
..
> The code you sent before actually constructed a shapeObj instead of a
> rectObj for the queryByRect.
> This is probably a legal thing to do but I just have to ask - are you
> sure the queryByRect is producing the correct result?


Yeah, I think I mistyped the code in my email message, however, the
problem still exists. Here is what I do... I create a circle shape with
its origin on the mouse click, and use it to select features from
another layer. I have $x0, $y0, and $radius (in map units, of course).

my $idlayerObj = getLayerByName("somelayer");
my $shpObj = new mapscript::shapeObj($mapscript::MS_SHAPE_POLYGON);
my $lineObj = new mapscript::lineObj();
my $pointObj = new mapscript::pointObj();
# make a circle
for (my $i = 0; $i <= 360; $i = $i + 10) {
  $pointObj->{x} = $x0 + (cos($i * (22 / 7) / 180) * $radius);
  $pointObj->{y} = $y0 - (sin($i * (22 / 7) / 180) * $radius);
  $lineObj->add($pointObj);
}
$shpObj->add($lineObj);
$idlayerObj->queryByShape($mapObj, $shpObj);
my $numbyshape = $idlayerObj->{resultcache}->{numresults};

The above results in $numbyshape equal to several hundred. That is wrong
given my data. So, I do the following --

$shpObj->setBounds;
my $rectObj = $shpObj->{bounds};
$idlayerObj->queryByRect($mapObj, $rectObj);
my $numbyrect = $idlayerObj->{resultcache}->{numresults};

This results in $numbyrect being the more correct 10 or 12.

Yup, the latter is correct... The data are essentially parcel centroids
being selected in a 200 ft radius of the mouse click... 10-12 parcels
within a 400 feet diameter circle makes sense. Not only the latter
selection is correct, the shape and the selected points also draw
correctly... The circle with 10-12 centroids within that circle.

Strange.



..
> > 
> > I've added this in the bz as an enhancement request. Part of the
> problem is that us 
> > non-developers still have to first figure out whether or not our
> problem lies with us 
> > screwing up or with the code. We can only do that via the list. Of
> course, once it is 
> > determined that indeed the problem is a "bug" then it can 
> be added to
> the zilla.
> > 
> > 
> > For example, I am still having a problem with queryByShape, and I
> don't know if I am 
> > doing something wrong or if this is a bug.
> > 
> > My problem is thus --
> > 
> > creating an shapeObj and then using it to queryByShape 
> against a layer
> returns way 
> > more results than should.
> > 
> > getting the bounds of the above shape and creating a 
> rectObj and then
> using 
> > queryByRect against the same layer returns the correct number of
> results (way less 
> > than that returned by queryByShape).
> > 
> > now, I have to first determine if I am doing something 
> obviously wrong
> or if this is a 
> > bug. Then I can act accordingly.
> > 
> > Many thanks.
> > 
> > _______________________________________________
> > Mapserver-users mailing list
> > Mapserver-users at lists.gis.umn.edu
> > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> 
>