Investigation of reliability of the variance covariance matrices obtained from GIPSY-OASIS II v6.4 software for precise point positioning

Abstract

In recent years Precise Point Positioning (PPP) technique is one of the most important subjects in Geomatic Engineering. PPP technique needs only one Global Navigation Satellite Systems (GNSS) receiver thus users have preferred it instead of traditional relative positioning technique for several applications. Nowadays, scientific software generally has been used for PPP solutions and the Variance covariance (VCV) matrices estimated from software are very optimistic. The formal errors estimated from VCV matrices have major effects on statistical interpretation. VCV matrices derived from GNSS processing software play important role for deformation analysis and scientists sometimes need to scale VCV matrices. In this study, 10 continuously operating International GNSS Service (IGS) reference stations have been considered for 11 days dated 2014. All points have been analyzed by GIPSY-OASIS II v6.4 scientific software. It is aimed to estimate scale factor for the PPP results obtained from GIPSY-OASIS II v6.4 with considering different session durations as 2, 4, 6, 8, 12 and 24 hours. According to the results, the values of the scale factors raise depending on the raises in respect of session duration.

Keywords

• GIPSY-OASIS II v6.4,Precise point positioning,Variance covariance matrix,Scale factor,Reliability

Hassas mutlak nokta konumlamada GIPSY-OASIS II v6.4 yazılımı ile elde edilen varyans kovaryans matrisinin güvenirliğinin araştırılması

Abstract

Hassas Mutlak Konum Belirleme (Precise Point Positioning - PPP) tekniği, harita/geomatik mühendisliği uygulamalarında son yıllarda öne çıkan önemli konulardan birisidir. PPP tekniğinde konumu belirlenecek noktada yalnızca bir tek Küresel Navigasyon Uydu Sistemleri (Global Navigation Satellite Systems (GNSS)) alıcısının kullanılması yeterlidir. Bu nedenle kullanıcılar bu tekniği birçok uygulamada geleneksel bağıl konumlama yöntemine göre tercih etmektedirler. PPP tekniği ile yapılan çalışmalarda veri değerlendirme ve analiz aşamalarında günümüzde genellikle bilimsel yazılımlar kullanılmaktadır. Bu yazılımlardan elde edilen Varyans kovaryans (VKV) matrisleri ise çok iyimser sonuçlar vermektedir. VKV matrislerinden hesaplanan değerler istatistiksel yorumlamalarda önemli etkiye sahip unsurlardır. GNSS veri değerlendirmesi sonucunda elde edilen VKV matrisleri deformasyon analizi gibi jeodezik çalışmalarda kullanılmaktadır. Bu bağlamda araştırmacılar VKV matrislerini ölçekleme ihtiyacı hissetmektedirler. Bu çalışmada, Uluslararası GNSS Servis (International GNSS Service – IGS) ağına ait 10 adet sürekli gözlem yapan sabit referans istasyonlarının, 2014 yılına ait 11 günlük verileri GIPSY-OASIS II v6.4 bilimsel yazılımı kullanılarak PPP tekniği ile analiz edilmiştir. 2, 4, 6, 8, 12 ve 24 saatlik gözlem süreleri için GIPSY-OASIS II v6.4 PPP sonuçlarından elde edilen VKV matrislerine ait ölçek faktörü kestirilmesi amaçlanmıştır. Analiz sonuçlarına göre ölçek faktörü değerlerinin gözlem süresi arttıkça büyüdüğü gözlenmiştir.

Keywords

• Hassas mutlak konum belirleme,GIPSY-OASIS II v6.4,Varyans kovaryans matrisi,Ölçek faktörü,Güvenirlik

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