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SITE ZENITH PATH DELAYS

Introduction

Since June 2001 (GPS week 1110) Zenith Path Delay (ZPD) parameters are estimated for all EPN stations. A combined EPN solution is produced on a weekly basis using the daily SINEX TRO files of the EPN Local Analysis Centres (LACs). Starting with GPS week 1185 all current 16 LACs are contributing to this product.
As the result of the combination two files for each week 'wwww' are produced:

a summary file (EURwwww7.TSU) with some statistics about, e.g., frequencies of the analyzed sites and accuracies of a single AC solution, providing the feedback to the contributing LACs, and
the output file (EURwwww7.TRO) containing the combined troposphere estimates with a two hours sampling rate. The coordinates as a necessary part of this file, are taken from EUREF's official combined SINEX file. Hence, stations without estimated coordinates in the weekly SINEX file are not included in the combined troposphere solutions.

The troposphere-related files can be downloaded from the EUREF product directory at BKG since GPS week 1110.

Products

ZPD time series	ZPD biases time series	ZPD radiosonde time series
Zenith Path Delay time series extracted from weekly EPN troposphere combined solution.	Time series of Zenith Path Delay biases for the participating LACs.	Zenith Path Delay differences radiosonde data minus EUREF combination.
Updated weekly	Updated weekly	Updated weekly

Purpose : Show time series of ZPD parameters derived from the EPN combined solution	Purpose : Show the agreement of the individual EPN LACs ZPD solutions Visualize potential periodic signals Reflect changes in, e.g. used options, analysis procedures etc	Purpose : Validate EUREF combined Zenith Path Delay (ZPD) parameters with ZPD derived from radiosonde (RS) data at co-located sites Variations and differences are influenced by the horizontal distance between the two stations Time series of differences reflect changes in analysis strategy
Procedure : Combination of daily SINEX TRO files of the individual LACs solutions on a weekly basis Weak ZPD estimates of the individual LACs solutions are excluded beforehand because of a standard deviation exceeding 15 mm Outliers of the individual LACs solutions are excluded before the combination Site-specific solutions of a particular LAC are eliminated for single days if the standard deviation of the series exceeds 20 mm Single ZPD values of the combined solution exceeding a standard deviation of 20 mm are investigated for potential outliers	Procedure : EPN LACs are delivering estimated ZPD parameters on a daily basis These solutions are combined to the EPN combined (mean) solution considering the biases between the individual solutions (this way jumps will be avoided if single observations of the individual solutions are missing) The resulting daily biases show the agreement of the LACs individual solutions to each other and to the mean	Procedure : Download of RS data provided by EUMETNET, based on the EUREF-EUMETNET MoU Processing ZPD parameters (software provided by H. Vedel, Danish Meteorological Institute (DMI)) Geoid undulations at co-located sites are taken into account Differences at co-located sites for identical points in time

Introduction

Products

ZPD time series

ZPD biases time series

ZPD radiosonde time series