[Mapserver-users] RE: need some help with queryByPoint()

[Charlton Purvis]

Hi, Bhavana:

I'll assume that you're using MS 3.7.

First off, queryByPoint only returns an int.  See the mapscript
documentation:  "Returns MS_SUCCESS if shapes were found or MS_FAILURE
if nothing was found or if some other error happened (note that the
error message in case nothing was found can be avoided in PHP using the
'@' control operator)."

But having it return a 1 does imply MS_FAILURE.

But it looks like you're querying by the mouse click.  You need to
translate that in to georeferenced coordinates.  Something like:

function pixelToGeo($map,$x,$y) {
        # Convert x,y pixel values to georeferenced coords.  Returns a
        # pointObj.

        $minx = $map->extent->minx;
        $miny = $map->extent->miny;
        $maxx = $map->extent->maxx;
        $maxy = $map->extent->maxy;

        $dx = $maxx - $minx;
        $dy = $maxy - $miny;

        $width = $map->width;
        $height = $map->height;

        $dxpp = (double)$dx/$width;
        $dypp = (double)$dy/$height;

        $geox = $minx + $dxpp*$x;
        $geoy = $maxy - $dypp*$y;

        $pointObj = ms_newPointObj();
        $pointObj->setXY($geox,$geoy);

        return $pointObj;
}

Then you're ready for something like:

$my_point->setXY($HTTP_POST_VARS["mapa_x"],$HTTP_POST_VARS["mapa_y"]);
$geo_point = pixelToGeo($map,$my_point->x,$my_point->y);

if(isset($geo_point)) {
   @$layerObj->queryByPoint($geo_point,MS_MULTIPLE,0.10);
}
 else {
   @$layerObj->queryByRect($map->extent);
};

Let me know if that helps.

Charlton

-----Original Message-----
From: Bhavana Rakesh [mailto:Bhavana.Rakesh at noaa.gov] 
Sent: Wednesday, July 23, 2003 11:00 AM
To: Charlton Purvis
Subject: need some help with queryByPoint()

 Hi Charloton,
I got your email from the mapscript question archives. I hope I'm not
imposing by sending you this email.  I have all the data stored in the
dbf file, but when I run the  queryByPoint no results are being
returned.
Any pointers will help.  I have attached the code and the error message
that
i'm getting when i try to use the queryByPoint function.  Please do
reply at your earliest conveniece if you know the answer.

function query_map($map, $global_layer){
        $layer = $map->getLayer($global_layer);
        $layer->set("status",MS_ON);
        printf("x,y co-ords are ". $_POST['mapa_x']."
".$_POST['mapa_y']);
        $m_point = ms_newpointObj();
        $m_point->setXY($_POST['mapa_x'],$_POST['mapa_y']);
        $queryresult = $map->queryByPoint($m_point,MS_MULTIPLE,-1);
        print("queryresult ". $queryresult);
}
The $queryresult prints out a 1.

The error message from the php log files :-
PHP Warning:  MapServer Error in msQueryByPoint(): No matching record(s)

found.
Would you know where I'm going wrong.  Any pointers will help.
Regards - Bhavana