if (mapContent != null) {
crs = mapContent.getCoordinateReferenceSystem();
}
displayCRS(crs);
mapPane.addMapPaneListener(new MapPaneAdapter() {
@Override
public void onDisplayAreaChanged(MapPaneEvent ev) {
ReferencedEnvelope env = (ReferencedEnvelope) ev.getData();
displayCRS( env.getCoordinateReferenceSystem() );
}