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GPSoft Position Solution

The SatNav Toolbox provides functions and example programs that allow the user to perform position determination based on real pseudorange measurements and broadcast ephemeris data, in RINEX format.

In the example shown here, data was obtained from a continuously operation reference station (CORS) located in Athens, Ohio. Stand-alone (i.e., non-differential) position solutions were calculated using the C/A-code pseudorange measurements. With no tropospheric or ionospheric corrections applied, the horizontal position error is still within +/- 5 meters:

GPSoft Plain CA Solution Horizontal

The following plot shows the separate position error components:

GPSoft Plain CA Solution East, North, Up

As would be expected, the vertical error is significantly larger than the horizontal error components.

If a simple (i.e., elevation-angle dependent only) tropospheric correction model is applied along with the broadcast ionospheric correction model, the horizontal position error does not seem to improve significantly:

GPSoft Corrected CA Solution Horizontal

However, examination of the individual components clearly reveals a significant reduction in vertical error:

GPSoft Corrected CA Solution East, North, Up

Since the tropospheric and ionospheric errors are composed primarily of biases, the impact is focused on the receiver clock solution and the vertical position error.

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