Estimation accuracy analysis of zenith tropospheric delays obtained by precise point positioning technique
At present, the number of application domains of global navigation satellite system (GNSS) receivers increased. Besides the tasks requiring high precision positioning such as geodesy, navigation, autonomous control of equipment, navigation data is used to such atmospheric parameters monitoring as integral water vapor content, pressure, tropopause height. Another example of the GNSS employing receiver, beyond the tasks associated with the consumer positioning, is track delay integration, obtained from the receiver with microwave radiometer measurements with the view of high-precision estimation of the tropospheric delay wet component for altimetry products An accurate calculation of the values of zenith tropospheric delays can be obtained by the Precise Point Positioning (PPP) technique. PPP technique is a secondary measurement processing method allowing achieve centimeter positioning accuracy with a single GNSS receiver. The values of zenith tropospheric delays (ZTD) herewith will be estimated directly in the Kalman filter with the rest unknown values such as position, clock offsetting and velocity. Due to the growing interest in this positioning technique, associated mainly with the possibility of its application in various fields, many ready-made algorithms for its implementation exist, both as online services and as software packages. This article presents a comparative analysis of estimates accuracy of zenith tropospheric delays obtained by navigation measurements processing from the four ground-base stations of the International IGS network with three software products, namely gLAB, CSRS-PPP and MagicGNSS. Zenith tropospheric delays estimated by this means were compared with reference tropospheric delays in the “*.zpd” format, provided by the International GNSS service. The presented study revealed two basic tendencies. Firstly, it was found that MagicGNSS and CSRS-PPP software products allowed obtaining ZTD estimates rather close to the IGS tropospheric product value. Secondly, the dependence between the time of year and zenith tropospheric determining delay accuracy was revealed.