num
Returns the number of levels closest to the specified resolution, but does not exceed it. May be used to configure level sets where a not to exceed resolution is mandated. The result is correct for this configuration's current firstLevelDelta, tileWidth and tileHeight, and is invalid if any of these values change.
Return
the number of levels
Parameters
radians
the desired not to exceed resolution in radians per pixel
Throws
If the resolution is not positive