How Accurate is GPS? Accuracy vs. Simulated Precision
It is common to assume consumer smartphones provide centimeter-accurate positioning. In reality, physical satellite positioning is subject to atmospheric refraction, urban multipath bounce, and antenna physics. Understand the crucial difference between mathematical coordinate precision and true ground accuracy.
Mathematical Precision vs. Ground Truth Accuracy
Coordinate Precision (Floating Point)
A computer can print a coordinate with 8 decimal places: 37.77492942. The 8th decimal place represents 1.1 millimeters. But having extra decimals on a screen does not mean a phone knows where you are within a millimeter.
Physical Accuracy (Ground Truth)
Under open sky, standard consumer smartphone single-band (L1) GPS chips typically have an accuracy radius of 3 to 5 meters (95% confidence). In urban canyons surrounded by skyscrapers, accuracy frequently degrades to 15 to 30 meters.
4 Physical Factors Governing GPS Accuracy
Why physical signals drift in the real world.
Dilution of Precision (DOP)
When satellites are widely dispersed across the horizon (low HDOP < 1.5), triangular intersection vectors yield tight fixes. When satellites cluster in one section of the sky, triangulation error multiplies dramatically.
Multipath Interference
Radio waves bounce off mirrored glass office towers, canyon walls, or damp asphalt before reaching the receiver antenna. The reflected path is longer than the direct path, causing positional jumps of 20 to 50 meters.
Ionospheric Delay
Solar radiation charges particles in the ionosphere, refracting radio waves and altering the speed of light slightly as satellite signals transit the upper atmosphere toward Earth.
Antenna Size & Ground Planes
Phone chassis must squeeze antennas into compact frames next to batteries and cameras. Dedicated external receivers (such as Mockery GPS ESP) utilize large ceramic patches with metallic ground planes that reject multipath signals.
How Mockery Handles Accuracy
Mockery is committed to technical honesty:
- In Simulation Mode (Web Controller): Coordinates follow deterministic mathematical geodesic curves at your designated speed.
- In Hardware Mode (GPS ESP): Mockery accurately passes through whatever physical accuracy radius, satellite count, and HDOP your hardware GNSS module reports via NMEA sentences—without fabricating false precision.
Explore External GPS Hardware
Learn how connecting an external antenna via ESP32 can improve satellite reception in vehicles.