You may have recently noticed some new behavior when zooming in to larger scales in the ArcGIS Online basemaps. Previously, in areas that lacked content at large scales, you would get a gray box with a “Map data not yet available” label. While technically correct, this made the user experience disjointed when panning and zooming in the map.
Now, thanks to “tile resampling”, introduced in early March 2014, the browser resamples the last cache level; effectively just enlarging the last cache “picture” it has available. This enables the map to display data uniformly down to the largest scale level of the particular ArcGIS Online basemap service being viewed. For example, the Topographic basemap displays data down to scale level 19 (1:1028). If you are zoomed to an area that only has data to scale level 18 (1:2257) that display of the map will be resampled so that it will display when zooming to 1:1028. Other basemaps that are designed to work at smaller scales (such as the Light Gray Canvas and National Geographic maps) will resample tiles all the way down to their largest respective scale levels (1:9,028 in the case of Light Gray Canvas and National Geographic). While you may notice the image losing sharpness as you zoom in on areas where tile resampling is taking place, we hope you agree that this is preferable to the old gray boxes and provides a much more consistent experience when working with the basemaps at all of their designed scale levels.
We plan to offer more details on this and other ArcGIS Online enhancements in a Community Maps webinar in the near future – perhaps April. So stay tuned!