05323322 is referenced by 326 patents and cites 6 patents.

An embodiment of the present invention relates to a worldwide network of differential GPS reference stations (NDGPS) that continually track the entire GPS satellite constellation and provide interpolations of reference station corrections tailored for particular user locations between the reference stations Each reference station takes real-time ionospheric measurements with codeless cross-correlating dual-frequency carrier GPS receivers and computes real-time orbit ephemerides independently. An absolute pseudorange correction (PRC) is defined for each satellite as a function of a particular user's location. A map of the function is constructed, with "iso-PRC" contours. The network measures the PRCs at a few points, so-called reference stations and constructs an iso-PRC map for each satellite. Corrections are interpolated for each user's site on a subscription basis. The data bandwidths are kept to a minimum by transmitting information that cannot be obtained directly by the user and by updating information by classes and according to how quickly each class of data goes stale given the realities of the GPS system. Sub-decimeter-level kinematic accuracy over a given area is accomplished by establishing a mini-fiducial network.

Title
Networked differential GPS system
Application Number
7/846380
Publication Number
5323322
Application Date
March 5, 1992
Publication Date
June 21, 1994
Inventor
Leonid Sheynblat
Redwood City
CA, US
Rudolph M Kalafus
Los Gatos
CA, US
Peter V W Loomis
Sunnyvale
CA, US
K Tysen Mueller
Cupertino
CA, US
Agent
Thomas E Schatzel
Assignee
Trimble Navigation
CA, US
IPC
G01S 5/02
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