A Global Positioning System includes a ground monitoring network having a plurality of dual frequency receivers that obtain ionospheric delay measurements to provide double difference ionospheric delay residuals. These double difference delay residuals are converted to zero differences based upon a new mathematical technique. The zero differences are fit to measurement epoch specific and transmitter specific mathematical surfaces (i.e. planes). These planes represent precise ionospheric delay corrections in the area of the ground monitoring network for a specific transmitter at the measurement epoch. The planes are then provided as correction information for use by inexpensive single frequency receivers to obtain highly accurate corrections for single frequency receivers by interpolating the correction planes to the location of the single frequency receiver. With this technique higher accuracy surveying results can be achieved with low cost single frequency receivers in real-time or in post-processing than what is currently achievable even with more expensive dual frequency receivers.

A meteorological electromagnetic measuring system contains a plurality of measuring stations which are physically distributed in a given area. Each measuring station contains at least one spherics receiver to pick up spherics signals and a transmission device to transfer measuring data available in the measuring station and derived from the spherics signals to a central evaluation unit assigned to the measuring stations. The measuring stations are disposed such that an average distance between adjacent measuring stations is less than 50 km for area wide detection of short-range spherics signals.

A system for analyzing three-dimensional seismic data includes a plurality of digitizer units, each with a configuration of geophones, a data recording and control center, a base GPS receiver with an associated antenna with a substantially unrestricted view of the sky and at the respective digitizer units low-power slave GPS receivers that acquire and track GPS satellite signals using tracking assistance information provided by the base GPS receiver. The slave GPS receivers use the tracking assistance information to acquire and track GPS satellite signals from which the slave GPS receivers produce associated range information. The system batch processes the range information provided by the slave GPS receivers over an extended period of time to determine the precise positions of the respective slave GPS receivers. The system provides the position information to the slave GPS receivers, and the receivers locally produce associated timing signals that are based on the GPS codes. If a particular slave GPS receiver cannot, at a given time, track any GPS satellite signals, a nearby slave GPS receiver supplies timing information required for the geophone data gathering operations.

A deformation monitoring system includes a data recording and control center, one or more base receivers with associated antennas that have a substantially unrestricted view of the sky and acquire and track satellite signals used for global positioning and slave receivers at various locations over the site being monitored, the slave receivers also acquiring and tracking the satellite signals. The system processes range information provided by the slave receivers over an extended period of time to determine the positions of the respective slave receivers. In this way, the precise positions of the respective slave receivers can be calculated, even if the slave receivers are able to observe and collect data from one or more satellites for only three or four relatively short time intervals at various sky positions during the extended period.

A set of Application Program Interfaces (APIs) for a resource-limited environment are disclosed. The APIs provide a mechanism for a computer application to interface with various components and modules of an operating system for a resource-limited environment. The APIs further provide a mechanism to interface with input/output devices commonly found in embedded systems running in a resource-limited environment.