Atmospheric models from GPS data

Ruggiero, V. and Caputo, M. (1998) Atmospheric models from GPS data. Il nuovo cimento C, 21 C (2). pp. 177-188. ISSN 1826-9885

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We modeled the atmosphere of the Earth, to 60 km elevation, with ten layers whose refractivity is given by N4ki exp [2h/hi] with h elevation over the surface of the Earth, ki and hi defining the refractivity of the layer. The refractivity is assumed continuous between layers, and this reduces the number of free parameters to 11 only. A programme is designed to generate synthetic travel times and from satellites distributed in space to a station on the Earth, travel times are generated with a standard atmospheric model. Stocastic errors are then assigned to the data. A programme is then designed to invert the synthetic data and to fit the travel time to the given satellite positions. The inverted atmospheric model, obtained with 60 satellite positions, deviates from the standard model by less than 4% of N; however, the deviations are positive and negative, the total effect is at most 0.01 ns in the travel time or 0.1 cm in the length of the path. The discrepancies between the model determined and the standard reference model are therefore almost irrelevant in the determination of the coordinates of the points on the surface of the Earth. The distribution of N is then used to infer tentatively the atmospheric water vapor content, the pressure and the temperature. The discrepancies resulting in the comparison obtained by fixing with standard models two of the 3 parameters, are not relevant and very encouranging for the use of GPS data to infer physical properties of the atmosphere. The discrepancy in the model water vapor content and that computed with the inversion is at most 1.2 mbar. A 10% variation of water pressure in the first 10 km of the atmosphere gives a variation 0.1 cm when measuring the elevation of the observing station. It also seen that restricting the observations to a 107 the arc of the orbit of the satellite, the atmospheric model obtained would not lose accuracy. The model suggested, determined by means of observations to GPS satellites, because of its 11 free parameters, instead of the two parameters of the standard model, will allow a more precise description of the real distribution of N at the time when the observations are taken and will therefore allow more precise corrections for the definition of the coordinates of the points on the surface of the Earth and of the positions of the GPS satellites.

Item Type: Article
Uncontrolled Keywords: Meteorology; instrumentation and techniques for geophysical research
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia > 551.5 Meteorologia (Classificare qui l'atmosfera) (Classificare la previsione e le previsioni di specifici fenomeni meteorologici in 551.64; classificare la Micrometeorologia in 551.66)
Depositing User: Marina Spanti
Date Deposited: 12 Feb 2018 12:25
Last Modified: 12 Feb 2018 12:25

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