there are no obvious traces of the fort or any other structures from croghan's homestead visible on the aerial photographs of the site. adding to the complications is the fact that old pennsylvania state route 522 could have impacted the fort and village sites. one way to focus the search for a compound structure such as fort shirley is to use geophysical prospecting techniques to detect any traces of subsurface features such as foundations, the palisade wall, and the powder magazine. after narrowing the search using the written record, maps, and gis; a geophysical survey was started in november 2009 with the help of indiana university of pennsylvania. a site grid has been established and the test blocks have been staked-out using a laser total station; then, ground-penetrating-radar and resistivity equipment were used to collect data during close interval traverses (0.5 or 1.0 m). the geophysical data will be interpreted further to help guide subsequent archaeological testing.