Nielsen Outdoor and its technology partner, RDP Associates, have developed a proprietary GPS device – the Nielsen Personal Outdoor Device, or Npod™ - about the size of a cell phone, which people carry in their pockets, purses or wear like a cell phone. Members of a randomly chosen sample carry an Npod as they move about on foot or in vehicles which is linked to orbiting satellites that enables Nielsen Outdoor to identify their location, speed and direction of travel, passively, continuously, easily and affordably.To determine actual exposure estimates to outdoor displays, we gather travel information of the routes taken by an individual which are matched to a list of geo-coded outdoor sites to obtain passages, or the opportunity to see specific outdoor sites. When the respondent's travel path intersects with a known outdoor site, an “intercept” is recorded, with each event dated and time-stamped, and the direction and speed of travel noted. This provides a robust set of data with the “opportunity to see” an outdoor display. This unique technology also enables Nielsen Outdoor to accurately measure exposure to transit advertising, or opportunity to see the outside advertising on any bus. (NIELSEN OUTDOOR)