1a. capture ALL mouse movement:
{
if (window.Event)
document.captureEvents(Event.MOUSEMOVE);
document.onmousemove = getCursorXY;
}
1b: function getCursorXY(e)
{
mouseX = (window.Event) ? e.pageX : event.clientX + (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft);
mouseY = (window.Event) ? e.pageY : event.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);
}
2. initialize the map with dragging=false
3. add map listeners for dragstart and drag
4. function dragstart()
{
dragX = mouseX;
dragY = mouseY;
}
5. function drag()
{
var dX = dragX-mouseX;
var dY = dragY-mouseY;
var rads = heading * Math.PI / 180;

map.panBy(dX*Math.cos(rads)+dY*Math.sin(rads), -dX*Math.sin(rads)+dY*Math.cos(rads));
dragX = mouseX;
dragY = mouseY;
}