[Chameleon] querytool and radius

Bart van den Eijnden bartvde at xs4all.nl
Sun May 15 08:01:35 EDT 2005

Hi list,

I have accomplished the first step of this process. I had some trouble  
getting a hang of the ROI API at first, I tried to use the draw method of  
the circle object, but I should have just added the circle roi object to  
the roi manager in order for it to draw. I am reporting back my solution  
to the list as I think this type of functionality is not really suitable  
for a general widget.

I followed the process which is described on the Wiki for plugging in your  
own query tool. My solution does need the following 2 widgets in the page  
(although the ROICircle tool should be invisible, but I am having some  
trouble getting it to behave invisible without getting a javascript error  
about the cwc_image ...).

Notice that I have set numberofpoints to 0 since I want to draw a direct  
opaque circle.

<cwc2 type="ROIManager" mode="normal" />
<cwc2 type="ROICircleTool" visible="true" styleresource="NavButtons"  
image="images/icon_roi_ellipse.png" imagetip="Define a circular ROI"  
toolset="Navigation" numberofpoints="0">
   <image state="normal"/>
   <image state="selected"/>
   <image state="hover"/>

Then in the javascript function which is triggered at the ON_QUERY event I  

function stragiswebquery( nX, nY )
   // radius in meters, todo: retrieve from form variable so user can change
   iRadiusGeo = 25;
   iRadiusPix =  

   goROICircleObj.centerX = nX;
   goROICircleObj.centerY = nY;
   goROICircleObj.radius = iRadiusPix;
   document.getElementById('TreeFrame').src =  
'/stragisweb/stragisquery.phtml?x='+ nX + '&y=' + nY + '&sid='  
+ document.forms[0].sid.value;

In the process I had to fix the following javascript bug in cwc_roi.js:

This draws a circle around the point clicked with the query tool using a  
radius of 25 meters. After this I want to pass the radius value to  
stragisquery.phtml and set the TOLERANCE of all the layers in the MAP file  
to this value using PHP/Mapscript. That should finish the functionality I  

Best regards,

On Fri, 13 May 2005 16:59:17 +0200, Paul Spencer <pspencer at dmsolutions.ca>  

> Cool!!!  I don't think it would take much to get it going ...
> Paul
> Bart van den Eijnden wrote:
>> Hi Paul,
>>  thanks for the reply. I knew about the buffer option in queryByPoint  
>> from dealing with Mapserver WFS lately.
>>  First I thought this would require changes to be made to the Chameleon  
>> core since executePointQuery in map_query.php does not take a  
>> radius/buffer argument.  But looking a bit further even buffers in  
>> meters would be possible without changes to the Chameleon core by  
>> setting TOLERANCEITEMS to METERS on the LAYER and a TOLERANCE on the  
>> LAYER object using PHP/Mapscript.
>>  Maybe I'll try to create this in the next weeks (for local layers).
>>  Best regards,
>> Bart
>>  Bart van den Eijnden
>> Syncera-ITSolutions
>> Postbus 270
>> 2600 AG  DELFT
>>  tel.nr.: 015-7512436
>> email: BEN at Syncera-ITSolutions.nl
>>>>> Paul Spencer <pspencer at dmsolutions.ca> 05/13/05 03:50pm >>>
>>  Bart,
>>  the radius is actually not used except in WMS queries and it is a  
>> vendor-specific-extension of WMS used by CubeSERV web servers ... I  
>> think there was a plan to add it to MapServer but I don't know if it  
>> ever happened.  Also, the radius is in pixels, not geographic units.
>>  I'm not sure if it is possible to do this out of the box with  
>> mapserver queries, but it would be a neat addition to Chameleon.  I  
>> just checked the php/mapscript docs and it seems that only query by  
>> point supports a buffer and it is in pixels.  Specifying a buffer in  
>> other coordinates would require a conversion to pixels at the current  
>> scale with an associated loss of precision
>>  The real solution to this will come with GEOS integration.
>>  Paul
>>  Bart van den Eijnden wrote:
>>> Hi list,
>>> does Chameleon have functionality for the following? I see there is a  
>>> radius attribute for the query tool which can be set by the developer,  
>>> but can it be set by the user?
>>> Can a user specify a radius in meters in an input field, and then when  
>>> he clicks in the map, similar DHTML functionality to the ROICircle  
>>> tool draws the circle on the map. The query is then performed within  
>>> this radius. If he resets the radius, and clicks again in the map, no  
>>> circle is drawn.
>>> If there is no functionality for this, how could it be created best?
>>> Best regards,
>>> Bart
>>> Bart van den Eijnden
>>> Syncera-ITSolutions
>>> Postbus 270
>>> 2600 AG  DELFT
>>> tel.nr.: 015-7512436
>>> email: BEN at Syncera-ITSolutions.nl  
>>> _______________________________________________
>>> Chameleon mailing list
>>> Chameleon at lists.maptools.org  
>>> http://lists.maptools.org/mailman/listinfo/chameleon

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