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|Title:||Comparative analysis of the effect of ionospheric delay on user position accuracy using single and dual frequency GPS receivers over Indian region|
|Authors:||Shukla, Ashish K|
Sivaraman, M R
|Keywords:||Ionospheric delay;Global Positioning System;Pseudo-range measurement;Single frequency receiver;Dual frequency receiver|
|Abstract:||The ionosphere acts as a prominent source of range errors for users of Global Positioning System (GPS) satellite signals requiring accurate position determination. Various models and mathematical formulations have been devised to calculate the absolute range error caused due to ionospheric delay. The present study aims at comparing two methods for calculating delay due to ionosphere: (i) using grid based model at L1 carrier frequency with bilinear interpolation technique; and (ii) using pseudo-range measurements at both L1 and L2 carrier frequency. For analyzing the effect of ionospheric delay on the seasonal behaviour of positional accuracy, a quantitative analysis has been done for all quiet days (Ap index < 50) in 2005 using GPS data for International GNSS Service (IGS) Bangalore (IISc) receiver in January, March and June. Various corrections such as satellite clock bias, transit time, ionospheric delay corrections, etc. are applied to pseudo-ranges to calculate the user coordinates. For single frequency (L1) receivers, ionospheric delay corrections have been applied using IGS total electron content data derived from grid based ionospheric model; and for the dual frequency receivers, pseudo-range measurements at L1 and L2 carrier frequencies have been used. It has been observed that there is an improvement of 1-4 m in the standard deviation of position errors when the ionospheric delay correction is applied using pseudo-range measurements at L1 and L2 frequencies (dual frequency receiver) as compared to L1 frequency only. It has also been observed that some residual errors still remain in the estimated user position even after using dual frequency receivers.|
|Appears in Collections:||IJRSP Vol.38(1) [February 2009]|
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