Add a feature to have a user add high resolution imagery from an online source. Instead of getting fuzzy images from Bing when you zoom in, you could load a High resolution map that better defines the area. Just have a spot where you can establish a link with a third party.
For example if using Pictometry, allow the user to incorporate their online database into Civil 3D. The bing maps could still be there but also add an option to switch to HR when desired.
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