public void notifyZoomLevel(final float zoomLevel) {
        if (this.zoomLevel.getValue() == null || Math.abs(zoomLevel - this.zoomLevel.getValue()) > 0.001f) {
            this.zoomLevel.setValue(zoomLevel);
        }
    }
LiveData wrapping the PositionHistory object or null if PositionHistory should be hidden
main/src/main/java/cgeo/geocaching/unifiedmap/UnifiedMapViewModel.java