Comparison of Observed Astrogeodetic Vertical Deflection Data Using QDaedalus System with the GGMplus- and EGM2008-predicted values in the Munich Region, Germany

Öz

Astrogeodetic vertical deflection (VD) data observed by astrogeodetic systems, which provide important information about Earth’s gravity field, are frequently used in the Earth Science disciplines, including geodesy and geophysics, to control and validate terrestrial, airborne and satellite gravity data. In this study, the total station-based QDaedalus system was used to observe astrogeodetic VD data at 10 benchmarks in the Munich region. The accuracy of these data is ~0.2 arcseconds (″). This high accuracy dataset was used to assess the quality of two global gravity field models—Global Gravitation Model Plus (GGMplus) and Earth Gravitational Model 2008 (EGM2008). The differences between the observed by QDaedalus and GGMplus-predicted VD data were ~0.2″ for both the North-South (N-S) and East-West (E-W) VD components, and reached a maximum of ~0.3″ and ~0.4″ for the N-S and E-W components, respectively. However, the maximum differences between the observed and EGM2008-predicted VD data for the N-S and E-W directions were 0.9″ and 1.8″, respectively. Thus, we found that the EGM2008-predicted values are less accurate than the predicted GGMplus values. The results of this study were compared with the results from a prior QDaedalus, and EGM2008 and GGMplus comparison study in Istanbul. In this article, we discuss the differences between the VD data obtained using the same QDaedalus system and global gravity field models in Istanbul and Munich, and explain the reasons for the higher accuracy of the VD data set predicted by GGMplus in both Munich and Istanbul.

Anahtar Kelimeler

• Astrogeodetic observations
• Astrogeodetic vertical deflections
• EGM2008
• GGMplus
• Global gravity field models
• QDaedalus

Almanya Münih Bölgesinde QDaedalus sistemi ile gözlemlenen astrojeodezik çekül sapma verilerinin GGMplus ve EGM2008 ile kestirilen değerlerle karşılaştırılması

Öz

Astrojeodezik sistemlerle gözlemlenen astrojeodezik çekül sapma verisi, yeryuvarının gravite alanı ile ilgili önemli bilgiler sağlaması nedeniyle, yerbilimleri alanında, özellikle jeodezi ve jeofizik gibi bilimsel disiplinlerde, yersel, hava ve uydu gravite verilerinin kontrolü ve validasyonunda sıklıkla kullanılmaktadır. Bu çalışmada, Münih bölgesinde yer alan 10 nirengi noktasında astrojeodezik çekül sapma verisi gözlemleyebilmek için total station temelli QDaedalus sisteminden yararlanılmıştır. Gözlemlenen verilerin doğruluğunun ~0.2 yaysaniyesi (″) olduğu saptanmıştır. Yüksek doğruluklu bu veri seti, iki global gravite alan modelinin—Global Gravite Modeli plus (GGMplus) ve Yer Gravite Modeli 2008 (Earth Gravitational Model 2008–EGM2008)—kalitesini değerlendirebilmek için kullanılmıştır. QDaedalus sistemi ile gözlemlenen ve GGMplus modeli ile kestirilen çekül sapma bileşenleri arasındaki farklar, hem Kuzey-Güney (K-G) hem de Doğu-Batı (D-B) bileşenlerinde yaklaşık 0.2″ olmakla beraber, maksimum farklar K-G ve D-B bileşenlerinde sırasıyla ~0.3″ ve ~0.4″ olarak tespit edilmiştir. Sonuçlar EGM2008 modeli için analiz edildiğinde ise, gözlemlenen ve EGM2008 ile kestirilen çekül sapma bileşenleri arasındaki maksimum farkların K-G bileşeninde 0.9″; D-B bileşeninde ise 1.8″ olduğu saptanmıştır. Dolayısıyla, EGM2008 ile kestirilen değerlerin, GGMplus ile kestirilen değerlere göre doğruluğunun daha düşük olduğu görülmüştür. Bu çalışmadan elde edilen sonuçlar, daha önce İstanbul’da QDaedalus gözlemleri ile EGM2008 ve GGMplus modellerinin kıyaslandığı uygulama sonuçlarıyla da karşılaştırılmıştır. Bu makale kapsamında, İstanbul ve Münih’te aynı sistem ve global gravite alan modelleri kullanılarak elde edilen çekül sapma verileri arasındaki farkların sebepleri tartışılarak, GGMplus ile kestirilen çekül sapma veri setinin, hem Münih hem de İstanbul’da daha yüksek doğruluğa sahip olmasının nedenleri açıklanmıştır.

Anahtar Kelimeler

• Astrojeodezik çekül sapması
• astrojeodezik gözlemler
• EGM2008
• Global gravite alan modelleri
• GGMplus
• QDaedalus

Kaynakça

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