Reduction of ionospheric effects on L-band InSAR measurements using GPS data
Zhenhong Li(1), Xiaoli Ding(2), S.Y. Ji(2) and W. Chen(2)
(1) University of Glasgow, University Avenue, Glasgow, G12 8QQ, United Kingdom
(2) Hong Kong Polytechnic University, Hung Hom, KLN, Hong Kong, China
The main advantage of L-band InSAR is that its coherence is generally better than C-band, particularly in heavily vegetated areas, due to its capability to penetrate more deeply in vegetation. However, since the ionosphere is dispersive, its impact on microwaves depends on the frequency of the signal and is ~17 times greater at L-band than at C-band. This indicates that caution needs to be exercised when interpreting L-band interferograms and ionospheric correction models should be explored.
It is well-known that dual-frequency GPS measurements can be used to derive the Total Electron Content (TEC) of the ionosphere that is believed to be applicable to reduce ionospheric effects on InSAR measurements. Based on our intensive experience in InSAR water vapour correction models and precise GPS data processing, a GPS-based ionospheric correction model is being investigated. The Southern California Integrated GPS Network (SCIGN) is one of the densest regional GPS networks in the world with stations distributed throughout southern California. It is particularly dense in the greater Los Angeles metropolitan region. The SCIGN inter-station spacing varies from only a few kilometers to tens of kilometers. Therefore, the SCIGN region is selected as the principal test area. It is expected that ionospheric signals with a wavelength of several kilometres or greater (i.e. GPS station spacing) are reduced using GPS-derived 2D TEC maps.
Acknowledgements: ALOS PALSAR data were provided through JAXA ALOS AO project (ID: P0610001; PI: I. Dowman).
*COMET: Centre for the Observation and Modelling of Earthquakes and Tectonics