Instantaneous geodetic positioning at medium distances with the Global Positioning System

We evaluate a new method of Global Positioning System (GPS) data analysis, called instantaneous positioning, at spatial scale lengths typical of inter station spacings in a modern crustal motion network. This method is more pr ecise and versatile than traditional GPS static and kinematic processing of multi-epoch batches of data. The key to instantaneous positioning is the a bility to resolve integer-cycle phase ambiguities with only a single epoch of dual-frequency phase and pseudorange data, rendering receiver cycle slip s irrelevant. We estimate three-dimensional relative coordinates and atmosp heric zenith delay parameters independently every 30 s over a 12-week perio d for baseline distances of 50 m, 14 km: and 37 km. Horizontal precision of a single-epoch coordinate solution is about 15 mm and vertical precision i s about 7-8 times worse. Removing that component of each time series which repeats with a period of exactly I sidereal day, and thus manifests signal multipath, reduces the scatter by about 50% in all components. Solution ave raging of the high frequency time series can be performed using: ally numbe r of measurement epochs to further improve coordinate precision. We demonst rate that the daily coordinates estimated with instantaneous positioning ar e more precise (by 20-50% per coordinate component) than those estimated wi th 24-hour batch processing. Spectral analysis of the single-epoch solution s indicates that the flicker noise characteristic of GPS time series observ ed in lower-frequency bands also affects GPS solutions in the frequency ban d 0.01 mHz to 10 mHz. We argue that the flicker noise is induced by troposp heric effects. Since modern GPS receivers are capable of observing at frequ encies as high as 10 Hz, our technique significantly overlaps and complemen ts the frequency band of broadband seismology and benefits other research a reas such as earthquake geodesy, volcanology, and GPS meteorology.