Hello:
As an additional consideration, I have noticed that in SBuilder, when one sees "normal / visible" aerial imagery tiles:
* at varying levels of zoom with a white image interspersed on zoom levels
at or below the maximum known available zoom for an area
...
or if:
* during a previous session (
ex: while reconnoitering an area before final downloading of additional contiguous tiles wanted for a project), then during a
subsequent aerial imagery tile download session one sees a white image for 'portions' of the project area interspersed at the same or varying zoom levels
...one may have to delete the tile folder for that
particular tile server to reset the tile info within SBuilder for ones project, as suggested here:
http://www.fsdeveloper.com/forum/threads/how-to-update-sbuilderx.316303/
However, it seems that the OP is describing use of tiles that were downloaded with GMAP
and loaded via SBuilder's "Add Map > From Disk.
IIUC, SBuilder does
not automatically attempt to "fill-in" zoom levels for such tiles using the built-in aerial imagery tile downloader feature when the project area is displayed using only tiles that were downloaded with GMAP and loaded via SBuilder's "Add Map > From Disk".
One might wonder, however, whether SBuilder may become 'confused' if one subsequently
adds aerial imagery tiles (using the built-in aerial imagery tile downloader feature) ...into the working set of tiles
already loaded via SBuilder's "Add Map > From Disk" in the displayed project workspace, and whether this might thus compel deleting one's tile folder for that
particular tile server to reset the tile info within SBuilder for ones project ?
Perhaps Dick might offer further comment on this possibility ?
UPDATED: I had not yet seen these threads at the "official SBuilder forum, which suggest that Google is now using different aerial imagery tile server URLs for various LOD / zoom levels, and this suggests that when such Zoom level imagery tile dropouts are seen, it may result in a need for Dick to issue an updated tile server DLL file:
http://www.ptsim.com/forum/viewtopic.php?f=30&t=2396
http://www.ptsim.com/forum/viewtopic.php?f=30&t=2393
Many thanks to Dick for continuing to help the FS community and SBuilder users over the years !
GaryGB