an open traverse starts on one known point and ends on another known point. That you don't know what it is tells me you don't know enough about it to be computing it.
It's a surveying thing.
Look at the "COGOEditor" tool in Civil 3D 2012 and 2013. It can be used to input the traverse and then adjust it. It can also read a polyline as the initial input. It likes COGO points, but can also work by picking locations in the drawing. There are a number of different options on how to balance the traverse after it is input.
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