@Override
    protected void onStart() {
        super.onStart();

        // close outdated details popups & restart sheet (if required)
        sheetManageLifecycleOnStart(viewModel.sheetInfo.getValue(), sheetInfo -> viewModel.sheetInfo.setValue(sheetInfo));

        // resume location access
        resumeDisposables.add(geoDirUpdate.start(GeoDirHandler.UPDATE_GEODIR));
    }
to be called by map fragments' observers for zoom level change
main/src/main/java/cgeo/geocaching/unifiedmap/UnifiedMapActivity.java