Getting coordinates from draggable_element

I tried to get the coordinates of a draggable_element.

I found in this topic a way to get the coordinates but i don't know what
i must set in the action reposition

at the moment i only have this

<div id ="dragDIV" class ="picture box">Verplaats de afbeelding naar de
gewenste plaats</div>
<%= draggable_element :dragDIV, :snap => 10, :ghosting => true
%>

<%= drop_receiving_element("dragDIV",
:url => { :action => "reposition" },
:loading => visual_effect(:highlight),
:update => 'admin_status_message',
:with => "'id=' + encodeURIComponent(element.id)
+ '&x=' + encodeURIComponent(Element.getStyle(element,'left'))
+ '&y=' + encodeURIComponent(Element.getStyle(element,'top'))
+ '&w=' + encodeURIComponent(Element.getStyle(element,'width'))
+ '&h=' + encodeURIComponent(Element.getStyle(element,'height'))") %>