Global positioning system measurements for crustal deformation: precision and accuracy

Area of Science:

• Geodesy
• Geophysics
• Satellite Navigation

Background:

• Precise positioning is crucial for various scientific and engineering applications.
• Global Positioning System (GPS) technology offers a powerful tool for geodetic measurements.
• Understanding the accuracy and limitations of GPS is essential for reliable data interpretation.

Purpose of the Study:

• To quantify the precision of Global Positioning System (GPS) measurements for position-difference vectors.
• To assess how measurement uncertainty varies with vector length.
• To compare GPS-derived distances with those obtained from other geodetic instruments.

Main Methods:

• Repeated GPS observations were analyzed for position-difference vectors.
• Standard deviations for north, east, and vertical components were calculated.
• GPS measurements were cross-validated with Geodolite and very long baseline interferometry (VLBI) data.

Main Results:

• For vectors up to 11 km, standard deviations were 4 mm (north), 6 mm (east), and 10-20 mm (vertical).
• Uncertainty increased gradually with vector length; at 225 km, standard deviations were 6 mm (north), 11 mm (east), and 40 mm (vertical).
• GPS measurements agreed within 0.2 ppm with Geodolite (10-40 km) and 0.05 ppm with VLBI (225 km).

Conclusions:

• GPS provides highly accurate and precise measurements for geodetic applications.
• The performance of GPS is robust across various vector lengths.
• GPS measurements are consistent with other high-precision geodetic techniques.