I am updating woodlot polygons in ArcMap 10. Instead of editing individual verticies, is there a way to edit that is more like drawing part of a new shape (say if the woodlot has expanded only on one side). I'm looking for something similar to the trace tool but I'm working off a tiff image so trace doesn't work. I just want to trace the woodlot and have the existing polygon update to that new shape. Anything to make this task faster would be much appreciated!
Instead of moving individual vertices for a feature you can use the Reshape Feature tool on the Editor toolbar.
Depending on how accurate your polygons need to be you could also leverage remote sensing algorithms to automate polygon creation against aerial imagery that has 4 bands (fourth band that is NIR) or LAS lidar data sets, see:
you should be able to use map topolgy on single polygons.
Then the reshape, trace, and other tools will work on those objects.
Also the raster snapping on the arcscan toolbar may help you.