he GAGAN supplies two different sets of corrections: 1) corrected GPS parameters (position, clock etc.) and 2) Ionospheric parameters. The first set of corrections is user position independent - they apply to all users located within the GAGAN service area. The second set of corrections is area specific. GAGAN supplies correction parameters for a number of points (organized in a grid pattern) across the GAGAN service area. The user receiver computes ionospheric corrections for the received GPS signals based on algorithms which use the appropriate grid points for where the user is located. Further, the appropriate grid points may differ for each GPS satellite received and process by the user receiver as the GPS satellites are located at various positions in the sky relative to the user. The combination of the two sets of corrections allows for significantly increased user position accuracy and confidence anywhere in the GAGAN service area.

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