Weighted Dilution of Precision (WPDOP) with consideration of the range errors and elevation of GNSS satellites during the high ionospheric activity period for the equatorial region
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The Dilution of Precision (DOP) is used as a quality measure in satellite positioning since it shows the geometric effect that connects positioning and measurement errors. It is a scalar indicator on the quality of the least-squares solution given by the square root of the sum of the parameter estimate variances considering that the User Equivalent Range Error (UERE) is the same for all satellites. The DOP may represent the precision of the adjustment but on the other hand, it may not always reflect the GNSS position error faithfully as the user equivalent range error tends to be different for each satellite at any time instant. Therefore, DOP presents limitations to correlate with the position error since it takes into consideration only the satellite geometric formation and neglects signal transmission-related errors, which become dominant for low-elevation satellites. This study presented a new approach to use the DOP as a weighted element taking into consideration the elevation angle from the satellite for periods of high and low ionosphere activity in the equatorial region. For this, the BRAZ station was chosen from the Brazilian Continuous Monitoring Network (RBMC) as a study case. The reference coordinates used were acquired from the description file and are: x = 4114014.0848, y= -4550641.5491 and z = -1741444.0190. To evaluate the proposed method two years were chosen: 2014 and 2019. For each year, six days were analyzed, WPDOP showed a moderate positive correlation for 8 out of the 12 analyzed days, for the summer of 2014 it presented a negative correlation. Meanwhile, PDOP presented a weak/very weak correlation for 11 out of the 12 days analyzed. WPDOP presented a higher capacity of indicated the accuracy of the SPP.