Positioning Accuracy

Description Provided Comparisons

SPP/PPP Single Frequency solution

The single frequency approach uses both the Pseudo Range and Carrier Phase on the GPS L1 frequency.  The Pseudo Range observations are corrected for the ionospheric delay using the Klobuchar model. The carrier phase measurement is used through the graphic linear combination between the pseudo range and the carrier phase on L1 (G1P = (C1P + L1P)/2).

The single frequency solution is provided to demonstrate the ability of the algorithms to be used in environments (such as the aviation industry) where only L1 is available for positioning purposes.

PPP Dual Frequency Solution

The Dual frequency approach uses the Pseudo Range and Carrier Phase on L1 andL2. The first order ionospheric delay is corrected by using the ionospheric free combination for the pseudo ranges and carrier phase ranges.

The dual frequency solution is provided to demonstrate the ability of the algorithms to be used in high precision applications (such as in the offshore industry) where survey or geodetic grade receivers are available for positioning purposes.

Provided solutions for comparison:

Fixed weighting scheme (non-mitigated)

The fixed weighting scheme demonstrates the most basic weighting scheme where the stochastic model only differentiates between the Pseudo Range and Carrier Phase observations.

For the single frequency solution:

The standard deviation for the pseudo range on L1 is set to 1.5 meter and the standard deviation for the graphic linear combination of the pseudo range and carrier phase is set to 0.1meter.

For the dual frequency solution:

The standard deviation for the ionospheric free linear combination of the Pseudo Range observations is set to 1 meter and the standard deviation of the ionospheric free linear combination of the Carrier Phase observations is set to 0.01 meter.  

General Elevation based weighting scheme (optimized non-mitigated)

In the general elevation based weighting scheme the relation between elevation and weights has been determined using Variance Component Estimation for all satellites together, thus the stochastic model only differentiates by elevation angle and signal type.

Scintillation screening scheme(simple mitigated)

Based on the receiver provided or scintillation map provided scintillation information and the elevation angle, the ranges affected by scintillation are excluded from the solution when above a certain threshold (for S4, s? and elevation angle). The weighting scheme is the same as the PRN elevation based weighting scheme.

Carrier to Noise density ratio based weighting scheme (mitigated)

The thermal noise jitter (DLL and PLL) is obtained from the receiver reported (RINEX observation file) Carrier-to-Noise density ratio. The calculated thermal noise jitter is obtained using the standard thermal noise formula (atan descriminator).The jitter is then optimised using the same VCE method as in the elvation based scheme.

Scintillation Screening and Variance Component Estimation (VCE) scheme

Similar to the Scintillation screening scheme it uses a PRN based elevation based weighting scheme. Weights for ranges affected by scintillation (S4 and Phi60 value above the threshold) are recalculated using Variance component Estimation.