[vanpelt]

What does he mean by GPS? Is he just getting location info from the IP or using the browser geolocation API? I’ve run my fair share of surveys on mTurk and FigureEight. The best way to prevent scams are with honeypots. Always have a question or two deeper in the survey that seem quick and simple but require engagement. Be sure to change these questions often.

[shmageggy]

Yeah, it's standard practice for mturk experiments to have a catch trial or two and to exclude responses that answer incorrectly. All of the experiments I've seen in my field do this.

[your-nanny]

This emphasis on GPS is the strangest part to me. True GPS coordinates are not directly available, AFAIK, in most circumstances pertaining to mturk. Services might use IP address and other data to make a guess. Maybe those with more experience with geolocation can chime in.