Advanced Forward Link Trilateration (A-FLT) is a technology used in GPS systems to improve accuracy in determining the location of mobile devices, such as phones or vehicles. A-FLT works by using signals from multiple GPS satellites and measuring the time it takes for the signals to reach the device, which allows for a more accurate calculation of the device's location. This technology is particularly useful in urban areas where GPS signals can be obstructed or reflected, causing inaccuracies in traditional GPS positioning methods.