Lecturer: L. Costantino Date: 2008-03-13 10:30 Place: Aniara
Determination of the Ionospheric Delay on L band signals, from GPS data
As a radio navigation system, GPS is subject to the effects of a number of error sources such as ionospheric and tropospheric errors, orbital error, multipath, clock biases, and measurement noise. Among them, ionosphere error is the largest one. The ionosphere creates a delay in the received signal which can range from several metres to more than one hundred metres [Klobuchar, 1991]. This will seriously corrupt the positioning and time transfer results unless these effects are taken into account.
To mitigate the ionosphere effect, a number of ionosphere modelling methods have been developed. The Klobuchar ionosphere model is derived from the empirical knowledge of the long-term ionosphere behavior. It is designed for single frequency users in which the required model parameters are broadcast via the navigation message from the satellites. This model, used by the GPS of the Unitred States, is typically accurate to a few metres along the vertical direction at mid-latitude [Klobuchar, 1987].
The dual-frequency method is based on the dispersive property of the ionosphere and requires the use of a dual-frequency GPS receiver.
The major objective of this thesis is to formulate a suitable dual-frequency correction algorithm. The analisys show that the use of this ionospheric correction, in spite of the Klobuchar model, can provide more accurate positioning calculations at both middle and lower latitudes.
? Klobuchar, J. A., Ionospheric Time-Delay Algorithm for Single-Frequency GPS Users, IEEE Transactions on aerospace and electronic systems Vol. AES-23, No 3, pp 325?331, 1987.
? Klobuchar, J. A., Ionospheric effects on GPS, GPS World, 48-51, Apr 1991.
Created 2008-02-25 08:54:40 by Mats HolmstrÃ¶m Last changed 2008-03-07 08:28:06 by Mats HolmstrÃ¶m