What does DGPS stand for?

DGPS stands for Differential Global Positioning System. This technology is an enhancement to the Global Positioning System (GPS) that improves the accuracy of position information. While standard GPS provides position data with an accuracy of about 10 to 30 meters, DGPS can reduce positioning errors to as little as a few centimeters.

DGPS works by using a network of fixed ground-based reference stations that calculate the difference between their known, fixed positions and the positions provided by GPS satellites. This differential correction information is then transmitted to DGPS-enabled receivers, allowing them to adjust their calculations accordingly. This is particularly important in applications requiring high precision, such as surveying, navigation, and in certain maritime and aviation contexts.

Other options don't accurately represent the correct expansion. For example, while "Dynamic Ground Positioning System" or "Digital Guidance Positioning System" might sound plausible, they do not exist as recognized systems. "Descriptive GPS Service" is also not a valid term within the context of positioning systems. Thus, B is the correct choice as it properly identifies the enhanced system that allows for more precise GPS data usage.