Evaluación del Método Split-Spectrum con Imágenes InSAR para la Estimación de Diferenciales Ionosféricos (ΔTEC) en los Departamentos de Cundinamarca y Boyacá entre los Años 2007 y 2010

Abstract

In this work, a comparison methodology with GNSS data obtained from geodetic stations was carried out in order to evaluate the ionospheric module of ISCE (Split-spectrum) for the calculation of ∆TEC and ionospheric correction in interferometry works. The evaluation was carried out in a local area of ​​Colombia, in the departments of Cundinamarca and Boyacá, with images from the ALOS-PALSAR satellite, mostly in FBD mode and some in FBS mode between 2007 and 2010, identifying each of the days available on the vertex download server, based on their geomagnetic and ionospheric activity, in order to determine quiet and disturbed days. Then interferometric pairs (disturbed-quiet, quiet-quiet, disturbed-disturbed) were organized to observe the ionospheric effects in the interferogram in the different bandwidths. The seismic activity in the time intervals was also taken into account to rule out fringes due to earth movements. Using the ISCE software, the processing of the interferograms was carried out, incorporating the Split-spectrum ionospheric module with the filters and default configurations, in turn, the GNSS stations in the area were requested to generate the ΔTEC maps, according to the interferometric pair configurations. Finally, the correlation was made between the differential maps obtained by GNSS and Radar; The results show the difficulties of dividing the dispersive phase due to low coherence and image processing errors: In the four frames of interferogram 6 (disturbed-quiet), ionospheric effects were evidenced, although only two were divided the dispersive phase adequately.Finally, when we validate the results comparing the TEC maps with the GNSS data, we found that the correlation was 0.14 and 0.83 for the 070 and 080 band respectively, the low correlation of the 070 band is due to the development of the phase was not correct. Other interferograms were obtained (quiet-quiet, disturbed-disturbed) where the dispersive phase was apparently adequately calculated, however, the ionospheric involvement is not evident and the correlation with the GNSS TEC maps was very low, due to the ionospheric modulus of Interferometry does not adequately calculate ionospheric dispersive phases where the differential TEC between days is zero or very close to zero. The dispersive phase calculated by ISCE in these cases is due to other dispersive sources.