This is a very interesting trip and technical project. I have a few questions: Do you have any idea of how accurate your GPS lock is while you are taking readings (16ft 50ft)? Are you logging this information? Your GM tube is good for gamma radiation. Do you have any provisions to measure other types (beta, alpha or neutron)? What are the sensitivity thresholds of your GM tube? Are you able to tell if it is getting saturated? And on another geek level: Have you watched the Chernobyl Diaries (bad as a horror movie, good as a tour movie) and will you get your picture taken near the ferris wheel, bumper cars, swimming pool and other places seen by other photographic trips?
Have a good, safe trip and bring back some good data.