Correction of troposhere induced errors in global positioning systems

• US 20070027624A1
• Filed: 04/19/2004
• Published: 02/01/2007
• Est. Priority Date: 04/17/2003
• Status: Active Grant

• Current Assignee: Secretary of State For Defence
• Original Assignee: Secretary of State For Defence
• Inventors: Butcher, James, Owen, John, Powe, Matthew
• Granted Patent: US 7,877,207 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01S 19/07 providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile

Abstract

A method of obtaining data for use by a receiver of a satellite positioning system or a GNSS comprises deriving the data remotely from the receiver by a server (200), using meteorological information and a regional or global three dimensional map of grid points from which it computes tropospherical delays by ray tracing through the refractivity field derived from atmospheric measurements of pressure, temperature and water data content, such measurements being available from meteorological bodies. When used to enhance position determined by a user receiver that includes a non-meteorological, climate based model (130) giving zenith delays and means (130′) to map them to particular inclinations, the server also includes a copy of such non-meteorological model (230) and provides its ray traced delay values as zenith delays. The sets of zenith delay values for corresponding grid points are compared in the server (260) and modifications developed (preferably in fractional form) by which the non-meteorological delay values require correcting to be accurate. The correction sets are reduced by image compression techniques (270) and transmitted via the satellites (110₁ etc) of the GNSS at low data rate to the user receiver, which receiver simply applies the corrections to the Zenith delays derived by its own model. If a user position is known, the server may derive accurate tropospheric delay values directly for the receiver position directly for transmission.

Claims

1. A method of obtaining tropospheric delay data for use in a satellite positioning system or GNSS by a user location comprising the steps of generating at a location remote from the user location, and from meteorological information, at least one accurate tropospheric delay value, applicable to the user location and either, with knowledge of the user position, generating said at least one accurate tropospheric delay value for the known user location for communication as a correct tropospheric dealy value to said user, or without knowledge of the user location, generating at least one tropospheric delay value presumed by a user to be applicable at a said unknown location then determining from the accurate and presumed tropospheric delay values a correction applicable to the presumed tropospheric delay values for communication as a tropospheric delay correction to a said user.

2-62. -62. (canceled)