public double getScaleForZoom(double zoom, String units) {
double resolution = this.getResolutionForZoom(zoom);
return OpenLayers.Util.getScaleFromResolution(resolution, units);
}
public double getZoomFromScale(double scale, boolean closest) {
double resolution = OpenLayers.Util.getResolutionFromScale(scale, getCurrentUnits());
return this.getZoomForResolution((Double) resolution, closest);
}