A permanent station GNSS reference RTK radio can transmit data directly to RTK receivers. The station will be monitored by a program running on a computer and will also allow the downloading and archiving of recorded data. Working radius of about 30 km is usually sufficient in this case and provides accuracies required. In special cases you can install a second or more permanent stations GNSS reference in order to ensure the attainment by two independent positions RTK receivers for determining certain critical points. In this case one computer (server) can provide control for all permanent stations GNSS reference.
To ensure accuracy centimeter networks Geodetic created by observation satellite, use and currently permanent stations temporarily, by installing a receiver in a network point and keep it fixed over several work sessions, or even for a whole day of observation. For relative positioning with high precision observations were used only in a situation where measurements were held near these stations in order to ensure control over the base length dependent bias. When designing permanent reference station networks GNSS is envisaged to serve a wider range of users, the optimal distance between these stations considering between 30 and 50 km.
This density is now regarded as insufficient. Network of permanent stations Cell Phone Tracker reference to US currently consists of 38 stations, the average distance between them is about. 200 km. A potential user of observations from these stations may be in the most unfavorable situation, about 100 km all GNSS reference stations standing around him. It is obvious that the holders of L1 receivers will not seek observations from these stations, with no possibility of control over the base length dependent errors. To avoid this inconvenience, technical positioning network of permanent stations sparsely been directed towards the realization of virtual reference stations.
This solution is a way to use all the information in real observations from permanent stations. The comments generated by virtual computing stations have much better characteristics compared to actual observations were carried out at these points as characteristic errors station (multipath, cycle-slip, refractions on the outskirts of obstructions) no longer exists. The functional programs that generate comments virtual stations using either linear equations to be an observation phase double difference equations. For generating virtual stations observations are necessary theoretical framework of this station, which is usually choose the center of your work area.
Data from neighboring real permanent stations are centralized on a single computer observations and worked jointly estimating ambiguities for each satellite in hand which is then extracted from the observation equations. Resulting equations containing only comments corrections, so equations reduced by satellite-receiver distance. If all observations have been reduced to a single station, the corrections obtained can be used to interpolate corrections for any other station on the network.
In the second phase, the information obtained is used to generate the virtual station accurate observations. The most difficult problem here is the modeling correct errors of observation. The modeling is done independently for each satellite in part, using flat correction, which corresponds to a two-dimensional linear interpolation. If three base stations are used the actual surrounding a virtual reference station, they form a triangle, and the area is uniquely determined by interpolation. Correction surfaces are described by two parameters that describe the interpolated surface tilt directions North and East. Modeling the influence of ionospheric refraction modeling is independent of the influence of tropospheric refraction errors and orbital so that each surface interpolation parameters are obtained in April expressed in ppm. Ionospheric refraction corrections to refer only to L1 signal.
In conditions in which all calculations are performed centrally, just a user to transmit the position of station virtual work area, being the offered remarks station virtual RINEX format, which can then be processed together with observations of real network, using a joint post-processing of satellite observations.
The great advantage of this technique lies in the fact that the short base is determined, which can be processed even for receivers with L1 frequency. This technique would be to create a solution and geodetic observations points higher order located in the woods, where they can make real observations in points in very inaccessible areas, or areas that were destroyed.