GPS Accuracy Estimator

GPS accuracy is the product of two independent things: how good the satellite geometry is (dilution of precision) and how good the underlying range measurement is (UERE, then whatever correction service refines it). This calculator derives HDOP and VDOP from the single GDOP value you enter (fixed splits of 70% and 85% of PDOP, which is itself 80% of GDOP), then multiplies Receiver UERE by HDOP, the Correction Method's accuracy factor, and the Multipath Environment factor to get horizontal error. Correction Method dominates every other input by a wide margin because its factors span nearly three orders of magnitude — standalone GPS applies a multiplier of 1.0, SBAS/WAAS cuts it to 0.4, differential GPS to 0.15, and RTK to 0.005, so switching from standalone to RTK at the default settings improves horizontal accuracy from about 6.7 meters to about 3 centimeters.

GDOP and Receiver UERE both scale the result directly and linearly — halve either one and horizontal/vertical accuracy both halve with it. Satellites Tracked and Elevation Mask are declared inputs on this page, and both are genuinely meaningful GNSS concepts (more visible satellites and a lower mask generally improve real-world geometry), but this calculator's formulas never read either value — GDOP is the only geometry figure the math actually uses, so changing satellite count or mask angle here does not move any output. Enter a GDOP that already reflects your real satellite geometry rather than expecting this tool to derive one from satellite count.