DGPS based systems are in work. Very few airports are surveyed to the accuracy required to 'blind taxi' - but work is in progress to survey the busy airports.
Initial requirements for such systems are being developed and refined - but the 'standards' don't exist yet. The guidance systems using the precise maps are in preliminary design and evaluation states as well.
Not "too many $$" is relative
It all takes time and money and is driven by a demonstrated economic case.
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Need a spell checker!
[ 06 October 2001: Message edited by: Narada ]