[GIS] Function to intersect another polygon using OpenLayers

intersectionjavascriptopenlayers-2

I wonder if someone here have a JavaScript function that when I draw a polygon I can see if I am drawing on another polygon?

like intersect… if polygon intersect say to me a alert…

using OpenLayers.

Best Answer

You can have a look at the intersection example of OpenLayers: http://dev.openlayers.org/examples/intersects.html

for(var i=0; i<features.length-1; ++i) 
{
    feat1 = features[i];
    for(var j=i+1; j<features.length; ++j) 
    {
        feat2 = features[j];
        intersects12 = feat1.geometry.intersects(feat2.geometry);
        if(intersects12) 
        {
        alert("Intersection");
        }
    }
}

Related Solutions

OpenLayers – Understanding Polygon Handler Function in OpenLayers

yourControl.events.register("featureadded", ' ' , controlFeatureHandler); 
...

function controlFeatureHandler(data)
{
    // do regular stuff


    // DISABLE control to draw
    yourControl.deactivate();
}

[GIS] OpenLayers – Get features inside a polygon

After some research I was able to find a solution. This function allows a user to draw an ad-hoc polygon and then interates through another WFS layer to locate any polygons that intersect the ad-hoc polygon. In my case I used this with WFS layers served from my GeoServer.

function buildIt() {//START FUNCTION buildIt

//CREATE A NEW EMPTY VECTOR LAYER 
var polygonAdHoc = new OpenLayers.Layer.Vector("Poly Layer");
//ADD THE NEW VECTOR LAYER TO THE OPENLAYERS MAP
map.addLayer(polygonAdHoc);
//SET A VARIABLE TO THE NAME OF THE EXISTING LAYER THAT WILL BE TESTED FOR INTERSECTION WITH THE USER CREATED POLYGON
//I CHOSE TO GET THE LAYER BY NAME BUT YOU MIGHT CHOOSE TO DO IT ANOTHER WAY
var standLyr = map.getLayersByName("nameOfTheVectorLayerYouWantToTestForIntersection");

//CREATE A DRAW FEATURE CONTROL FOR THE USER CREATED VECTOR LAYER
var draw = new OpenLayers.Control.DrawFeature(polygonAdHoc, OpenLayers.Handler.Polygon);
//ADD THE DRAW FEATURE CONTROL TO THE MAP
map.addControl(draw);
//ACTIVATE THE DRAW FEATURE CONTROL
draw.activate();

//WHEN THE USER FINISHES DRAWING THE AD-HOC POLYGON THE beforefeatureadded EVENT WILL FIRE
polygonAdHoc.events.on({
    beforefeatureadded: function (event) {
        poly = event.feature.geometry;//SET A VARIABLE TO THE USERDRAWN POLYGONS GEOMETRY
        //alert("polygonAdHoc.features[0].geometry: " + poly);//IF YOU WANT TO SEE THE GEOMETRY COORDINATES UNCOMMENT THIS LINE
        for (var a = 0; a < standLyr[0].features.length; a++) {//LOOP THRU THE STANDS FEATURES OF THE LAYER YOU WANT TO TEST FOR INTERSECTION WITH THE USER DRAWN POLYGON
            if (poly.intersects(standLyr[0].features[a].geometry)) {//IF THE USER DRAWN POLYGON INTERSECTS THE TARGET LAYERS FEATURE REPRESENTED BY THE VARIABLE "a" THEN
                 //IDENTIFY THE FEATURE THAT INTERSECTS 
                 //FOR SIMPLICITIES SAKE I CHOSE TO JUST FIRE AN ALERT
                 //MY ACTUAL APP ADDS EACH SELECTED FEATURE TO A SELECT FEATURE CONTROL AND HIGHLIGHTS EACH POLYGON ON THE MAP                
                 alert("stands feature intersection: " +  standLyr[0].features[a].attributes['nameOfAttribute']);
            }//END OF IF STATEMENT
        }//END OF FOR STATEMENT
        draw.deactivate();//I ONLY WANT THE USER TO BE ABLE TO DRAW ONE AD-HOC POLYGON
        //SO I DEACTIVATE THE DRAW FEATURE CONTROL AFTER THEY CREATE THE FIRST POLYGON
        return false;
    }//END OF beforefeatureadded FUNCTION
});//END OF polygonAdHoc.events.on
}//END OF buildIt FUNCTION

Best Answer

Related Solutions

OpenLayers – Understanding Polygon Handler Function in OpenLayers

[GIS] OpenLayers – Get features inside a polygon

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