Downloads imagery not currently available in the World Wind file cache or a specified file store. The class derives
from Thread and is meant to operate in its own thread.
The sector and resolution associated with the downloader are specified during construction and are final.
protected long estimateMissingTilesCount(int numSamples)
protected long getEstimatedMissingDataSize()
Get the estimated size in byte of the missing imagery for the object's Sector, resolution and file store.
Note that the target resolution must be provided in radian latitude per texel - which is the resolution in meter
divided by the globe radius.
the estimated size in byte of the missing imagery.