Often, I get questions from people who zoom in on a map and only see a blank grid. I'll show an example that will show how this may not be a bug.
Often the question is something like this: "Sometimes I zoom in on downloaded maps and all I see is a blank grid. What's wrong?" Often nothing.
There is a key rule to keep in mind when you define a rectangle for download:
The download will download all tiles that *overlap* the defined rectangle, for all zoom levels.
In the following screen, I've just completed a small download. Here it is at zoom level 15, the highest detail I specified when downloading.
This map adequately covers the rectangle I specified, plus more, so I should be extremely satisfied, right?
Now I'll try zooming out three levels to level 12. At this zoom level, the rectangle I specified overlaps exactly one (1) tile which covers a wide region.
Again, this more than adequately covers the region I specified, so I should still be satisfied. Now the interesting stuff happens if I pan around this zoom level and then zoom in. If I zoom in on the green circle above, I should expect to see some more detailed map data.
However, if I zoom in on one of the red circles above, something happens which I may not expect. The map "disappears" and all I see is a blank grid. I could be disappointed, or think this is a bug, but why? After all, I got the region I asked for.
User Actions to help
So if this isn't a bug, then what can a user do about it? Here are some suggestions:
- Download a larger region. You could mark a rectangle that completely surrounds the one tile at zoom 12, and then you could expect to zoom in fully at those red circles.
- Turn off "Offline Maps Only" in the Map Source menu to go back into preview mode. Then you can at least preview the areas with red circles, and any tiles downloaded during preview will be saved.
Where the App could help.
The use of tiling in maps is here to stay. Nonetheless, there are some good suggestions users have made:
- Show a coverage viewer that will allow you to see what your map currently covers. Presumably this will show a grid where darker squares indicate higher resolution.
- Show a grid and allow you to tap and choose tile squares instead of defining a rectangle. This will give you more predictable results, although it won't completely eliminate "zoom-in disappointment."
Look for some of these ideas in surveys and future updates.