GPS Distributed Aperture Positioning (GDAP)

The GPS signal is subject to a variety of potential degradations, such as path loss (e.g., foliated or indoor environments), multipath (e.g., urban canyon or inbuilding), and interference (intentional or unintentional). There are many applications, both commercial and military, where a group of GPS users may operate together in a denied or degraded GPS environment. Using the traditional GPS receiver approach, individual or all users may be denied the ability to navigate in such an environment, even though each user may be intermittently receiving useful satellite signal information. To address this issue, NAVSYS developed a design for a GPS Distributed Aperture Positioning (GDAP) system which uses composite GPS and intra-network ranging measurements from a network of GPS users to combine the respective satellite signals they are tracking and allow operation in a degraded environment.