Historic archaeology using GPR and EM (Electromagnetic Conductivity)

We have collected many grids of GPR at historic sites, most of which are quite good.  Historic features tend to be much more visible than prehistoric structures, because they are more intact, not as deeply buried, and often times have metal objects associated with them.  Here are two examples.

Bradford House, Colorado:  a historic house still remains, but there are many questions about whether any of the outbuildings are still present.  The historic photos show there to have been many structures, but none remains.  Here we are collecting data with an EM-38 in the fall of 2003.   The geophysical maps showed a number of interesting features, including a pipe to (or from?) the house (there is no documentation of indoor plumbing) and a trash midden.

Four Mile Historic Park, Colorado:  this park, 4 miles southeast of downtown Denver, contains the oldest house in the city.  We explored around it to see what might be left of the outbuildings, and found an interesting square structure in the orchard.  .  In the profiles the floor is just barely visible, but the pipe can be readily seen..  We excavated it in May, 2003 and found the pipe easily.  It was a recent plastic water pipe.  The floor was found to be just a 3 cm thick sand layer that was probably a base for a flagstone floor.  One small piece of flagstone was found on the sand layer, but the rest appear to have been pulled up to recycle when the structure was abandoned.  This is an interesting example because it shows how GPR is capable of locating these kinds of subtle features that are barely visible to the human eye.  In fact, when we excavated it, if we didn't know it was there and were looking for the floor, we would have just thought it was a sandy layer in the ground, and not paid much attention to it!

The Ferry House: Whidbey Island, Washington

This old house had a number of interesting features surround it, including the old well, and a pile of metal out in a field, that we don't know the origin of.  Also, there were some really interesting prehistoric features visible in the data, including roasting pits.