What is the accuracy of the Military's GPS and DGPS?

• A. GPS within 10 meters; DGPS within 5 meters
• B. GPS within 20 meters; DGPS within 10 meters
• C. GPS within 1 meter; DGPS within 0.5 meter
• D. GPS within 50 meters; DGPS within 25 meters

Answer: (A)

GPS accuracy comes from how precisely the receiver can measure satellite signals and correct for errors such as satellite clock timing and atmospheric delays. In the common military training context, a standalone GPS fix is described as about 10 meters in horizontal accuracy. When differential GPS is used, corrections from a nearby fixed reference station with a precisely known position are applied to the pseudorange measurements, which typically improves accuracy to around 5 meters. This improvement happens because the reference station cancels out many of the same error sources that affect all receivers in the area, allowing your receiver to compute a much more precise location.

Those numbers reflect standard performance under good reception conditions. Real-world results can vary with sky visibility, multipath, and equipment quality. The other option figures imply either unrealistically tight precision for ordinary DGPS or an overly coarse result; the 10 meters for GPS and 5 meters for DGPS are the commonly cited training values for military navigation contexts.