Effect of altitude and distance on zenith tropospheric delay and integrated water vapour estimations in a local GNSS CORS network

Öz

In this paper, to investigate the usability of Continuously Operating Reference Stations managed by the Istanbul Water and Sewerage Administration (ISKI CORS) for weather prediction studies, the effects of altitude and distance on Zenith Tropospheric Delay (ZTD) and Integrated Water Vapour (IWV) estimations were analysed. Within the scope of this study, the authors determined accuracies of ZTD and IWV values - based on the selected reference stations and analysed them for altitude and distance factors. GnSmart software is used for ZTD estimation as this software broadcasts CORS correction and GNSS Analysis and Positioning Software (GAPS) is used for IWV estimation. In this study, a single reference station was used to test the accuracy of ZTD and IWV values obtained from local ISKI CORS network stations (TUZL station for ZTD values and radiosonde station numbered 17064 for IWV values). The determined RMSE values could not reach the ZTD and IWV precision standards of the World Meteorology Organization (WMO). One reason for this is that a single station is selected as a reference. In short, the authors express that the ZTD and IWV values of ISKI CORS stations are not similar, but there is a significant difference between them. It was also understood that a single radiosonde station is not sufficient to determine the IWV values of the stations in the local ISKI CORS network, and the GNSS IWV values obtained from the stations can be meaningful.

Anahtar Kelimeler

• GNSS
• ISKI CORS
• Tropospheric delay
• Integrated water vapour

Lokal bir GNSS CORS ağında yükseklik ve mesafenin zenit troposferik gecikme ve entegre su buharı kestirimleri üzerine etkisi

Öz

Bu makalede, İstanbul Su ve Kanalizasyon İdaresi’nin yönettiği Uydulardan Konum Belirleme Sistemi’nin (İSKİ UKBS) hava tahmin çalışmalarında kullanılabilirliğini araştırmak için yükseklik ve mesafenin Zenit Troposferik Gecikme (Zenith Tropospheric Delay, ZTD) ve Entegre Su Buharı (Integrated Water Vapour , IWV) kestirimleri üzerindeki etkisi analiz edilmiştir. Çalışma kapsamında, yazarlar seçilen referans istasyonlara göre ZTD ve IWV değerlerinin doğruluğunu belirleyip mesafe ve yükseklik faktörlerine göre analiz etmişlerdir. ZTD kestirimi için CORS düzeltme yayını yapan GnSmart yazılımı, IWV kestirimi için ise GNSS Analiz ve Konum Belirleme Servisi (GAPS) kullanılmıştır. Bu çalışmada, yerel İSKİ UKBS ağı istasyonlarından elde edilen ZTD ve IWV değerlerinin doğruluğunu test etmek için tek bir referans istasyon kullanılmıştır (ZTD değerleri için TUZL istasyonu ve IWV değerleri için 17064 numaralı radyosonda istasyonu). Belirlenen RMSE değerleri Dünya Meteoroloji Örgütü'nün ZTD ve IWV presizyon standartlarına ulaşamamıştır. Bunun bir nedeni, referans olarak tek bir istasyonun seçilmesidir. Özet olarak yazarlar, İSKİ UKBS istasyonlarının ZTD ve IWV değerlerinin benzer olmadığını ancak aralarında anlamlı bir fark olduğunu ifade etmektedirler. Yerel İSKİ UKBS ağındaki istasyonların IWV değerlerinin belirlenmesi için tek bir radyosonda istasyonunun yeterli olmadığı, istasyonlardan elde edilen GNSS IWV değerlerinin anlamlı olabileceği de anlaşılmıştır.

Anahtar Kelimeler

• GNSS,
• İSKİ UKBS
• Troposferik gecikme
• Entegre su buharı

Kaynakça

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