It is an incomplete map but definitely not due to poor connections. Tried it in different countries and with good wifi and 3G connections. Still a problem.
It has been going on for several months. Tried the obvious things like resetting etc.
Been going on so long I am afraid I can't remember if anything such as an update precipitated the problem.
If I am zoomed into any normal level then the map is completely blank. Only if I zoom out to show the whole country do I start to see this ghostly outline.
The satellite view works fine and so usually does the hybrid view, especially if I've switched to satellite view first.
Also other Apps (eg DayOne) that use Apple's maps for location have a blank screen and they don't all have the option to use satellite view.