🔍 Key Concepts

• DGPS stands for a specific type of GPS enhancement system • How GPS accuracy is improved using correction signals from known reference stations • Difference between systems used for marine navigation versus aviation altitude

💭 Think About

• Think about what the letters in DGPS most likely stand for in the context of marine navigation, not just any plausible-sounding phrase • Consider how mariners improve the accuracy of ordinary GPS—what kind of information do they add to the basic GPS signal? • Ask yourself which option best matches a system used at sea to refine horizontal position, rather than height or altitude

✅ Before You Answer

• Verify which choice describes using correction factors to improve an existing GPS position rather than creating a whole new system • Eliminate any option that focuses mainly on altitude or aircraft, since this question is about marine use of GPS • Check that the description fits with shore-based or reference-station corrections typically associated with DGPS in maritime navigation