private async Task RefreshPolygonsAsync()
        {
            if (_visibleRegion == null)
            {
                return;
            }
            int layer = _hexagonal.CalculateLayerFromCameraPositionZoom(_currentCameraIdledEventArgs.Position.Zoom);

            if (layer != _layerLast)
            {
                Polygons.Clear();
                _layerLast = layer;
            }
            _hexagonal.Initialize(_currentCameraIdledEventArgs.Position.Target.Latitude, _currentCameraIdledEventArgs.Position.Target.Longitude, layer);
            for (int row = -2; row < 3; ++row)
            {
                for (int col = -2; col < 3; ++col)
                {
                    var poly = _hexagonal.HexagonalPolygon(_hexagonal.CenterLocation, col, row);
                    if (Polygons.Any(p => p.PolygonTagEquals(poly)))
                    {
                        continue;
                    }
                    int heatCount = _layerService.NumberOfUsersInsidePolygonTag(poly.ExtractPolygonTag().Tag);
                    poly.FillColor   = _heatGradientService.SteppedColor(heatCount);
                    poly.IsClickable = true;
                    poly.Clicked    += Polygon_Clicked;
                    if (poly.PolygonTagStringEquals(_currentPositionTag))
                    {
                        poly.StrokeColor = Color.Coral;
                        poly.StrokeWidth = 5;
                    }
                    else
                    {
                        poly.StrokeColor = _heatGradientService.SteppedColor(heatCount + 1);
                        poly.StrokeWidth = 1;
                    }
                    Polygons.Add(poly);
                }
            }
            await RefreshZonesAsync();
        }