406 MHz EPIRBS located from a LEO or MEO satellite are accurate within how many nautical miles?

• A. 1 NM
• B. 3 NM
• C. 5 NM
• D. 10 NM

Answer: (B)

When a 406 MHz EPIRB is picked up by a LEO or MEO satellite, the system determines the transmitter’s position by analyzing how the signal is received over time and from different viewpoints (Doppler shifts and time differences). The geometry and measurement uncertainties in this satellite-based localization yield a horizontal accuracy on the order of a few nautical miles. The standard figure used in SAR guidance is about 3 nautical miles, which is why that option is the best fit. If the beacon has GPS, the location can be much more precise (hundreds of meters or less), but without GPS the typical accuracy remains near 3 NM. The other options are outside the commonly expected range for this satellite-based method.