function checkedRadioBtn(){  
    for(var key in bilder_switched) {
        if(document.getElementById(key).checked){ 
            newL = new ol.layer.Image({source: new ol.source.ImageStatic(bilder_switched[key])});
            //remove image from map
            map.removeLayer(baseLayer);

            //get layers and remove marker
            var allLayers = map.getLayers().getArray()[0];
            map.removeLayer(allLayers);

            for(var i = 0; i<icons.length; i++){
                map.removeLayer(icons[i]);   
            }
            
            map.addLayer(newL);
        }
    }
};