Studies On The Applications Based The IGS VTEC Products

VTEC is one of several important parameters of ionosphere.The number of using IGS VTEC products has been increasing since the global grid ionospheric VTEC maps were published by IGS from Jun 1st,1998.We have been showed that using GNSS to study ionosphere has a long view.GNSS ionosphere product has many usages.Based on this product,the main works and inclusions are as follows:1.The procedure and tendenc y of IGS ionosphere products are introduced,and the inconsistencies between IGS ionosphere products and IONEX1.0 are pointed out to programming with these products.2.Concrete analyses have been done with BERN source codes.The deficiencies are also pointed out,such as errors will occur when the longitudes from-180oE to-150oE are input.3.Two basic programs are programmed based on studies on interpolating algorithms of VTEC maps.O ne is extract information from single day and the other one is extract information from many successive days.Their correctness is verified by some examples before being applied.4.Analyses are done by using minimum variance method based on VTEC series of different latitudes.The annual period,half of one year period,and 27-day period are founded again,another 11-day period is also founded.The results will be helpful to study ionosphere climate in depth.5.VTEC abnormal behaviors are detected by use of two different ways,the median method and the moving window method,for the Yaan earthquake on April 20 th,2013.Positive abnormalities are the main case,but negative abnormalities companied by increasing intensity and duration occurred during several days before the earthquake in that month.