Akıllı telefonların çok frekanslı çoklu-GNSS SNR verilerinin GNSS-IR performansının değerlendirilmesi

Year 2025, Volume: 12 Issue: 1, 1 - 19, 30.04.2025

Cemali Altuntaş , Nursu Tunalıoğlu

https://doi.org/10.9733/JGG.2025R0001.E

https://izlik.org/JA23CW48WM

Abstract

Akıllı telefonlar, birden fazla uydu sistemini destekleyen gömülü Küresel Navigasyon Uydu Sistemleri (GNSS) çipleri ile donatılmıştır. Bu durum konum belirleme, navigasyon ve zaman ölçümü çalışmalarında doğruluğu artırmaktadır. GNSS İnterferometrik Reflektometri (GNSS-IR) yöntemiyle, bu özelliklerden faydalanılarak yüzey özelliklerini daha doğru kestirmek için çok yolluluk etkisindeki sinyallerin ve yansımaların analizi gerçekleştirilebilmektedir. Çok frekanslı çoklu-GNSS veri toplama kabiliyetine sahip olmalarının yanı sıra, geleneksel jeodezik alıcılara kıyasla daha düşük maliyetli ve taşınabilir olmaları nedeniyle akıllı telefonlar, GNSS-IR çalışmalarında uygulama için önemli bir potansiyele sahiptir. Bu çalışmada, jeodezik alıcılar ve akıllı telefonlardan sağlanan çok frekanslı çoklu-GNSS SNR verilerinden elde edilen reflektör yüksekliği ve yükseklik değişimine ilişkin kestirimlerin doğruluğunu değerlendirmek için her gün altı saatlik ortak gözlem içeren üç günlük bir deneysel çalışma gerçekleştirilmiştir. 121Y348 numaralı TÜBİTAK projesi kapsamında geliştirilen deney düzeneğine, iki CHC i90 Pro jeodezik alıcı ve iki Samsung Galaxy Note 20 Ultra akıllı telefon, başucu ve ayakucu doğrultularına bakacak şekilde yerleştirilmiştir. Geçerli kestirim sayısı, pik-arka plan gürültü oranı değerleri, reflektör yüksekliği ve yükseklik değişimi kestirimlerinin doğruluğu üzerinden uydu sistemi ve frekans temelli değerlendirme yapılmıştır. Bulgular, jeodezik alıcıların GNSS-IR uygulamalarında veri toplama stabilitesi yönünden akıllı telefonlardan daha üstün performans sağladığını göstermiştir. Ayrıca, akıllı telefonların yöneliminin (düz, ters veya eğimli) GNSS-IR kestirimlerinin doğruluğu üzerindeki etkisinin çok az olduğu ve en stabil akıllı telefon verilerinin GPS uydularından elde edildiği görülmüştür. Buna ek olarak, 20 cm’den kısa dalga boyuna sahip sinyallerin akıllı telefon tabanlı GNSS-IR çalışmalarında kullanılmasının daha iyi sonuçlar sağladığı ve kar kalınlığı, deniz seviyesi ve bitki yüksekliği gibi iklimbilimsel parametrelerin uzun vadeli izlenmesi için düşük maliyetli bir alternatif teşkil ettiği tespit edilmiştir.

Keywords

Çoklu-GNSS , Çok yolluluk , GNSS-IR , SNR , Akıllı telefon

Project Number

121Y348

Assessment of GNSS-IR performance using multi-GNSS and multi-frequency SNR data from smartphones

https://izlik.org/JA23CW48WM

Abstract

Smartphones are equipped with embedded Global Navigation Satellite Systems (GNSS) chips that support multiple satellite systems, enhancing precision in positioning, navigation, and timing services. The introduction of GNSS Interferometric Reflectometry (GNSS-IR) leverages these capabilities by analyzing multipath signals and reflections to estimate surface properties more accurately. Given their multi-GNSS and multi-frequency capabilities, along with lower cost and greater portability compared to traditional geodetic receivers, smartphones hold significant potential for application in GNSS-IR technologies. In this study, we conducted a three-day experimental evaluation, observing for six hours each day to assess the accuracy of reflector height and change estimations from multi-frequency multi-GNSS SNR data provided by geodetic receivers and smartphones. The setup included two CHC i90 Pro geodetic receivers and two Samsung Galaxy Note 20 Ultra smartphones, positioned in both zenith-looking and nadir-looking orientations, facilitated by an experimental setup developed under TÜBİTAK project number 121Y348. Our analysis focused on the number of valid estimations, peak-to-background noise ratio (PBNR) values, and the accuracy of reflector height and height difference estimations with satellite-based and frequency-based assessments. According to the results, geodetic receivers consistently outperform smartphones in data collection stability for GNSS-IR applications. We also found that the platform orientation of smartphones (flat, inverted, or inclined) has a minimal impact on the accuracy of GNSS-IR estimations, and the most reliable smartphone data is obtained from GPS satellites. Furthermore, using signals with wavelengths shorter than 20 cm in smartphone-based GNSS-IR studies provides better results and offers a cost-effective method for long-term monitoring of climatological parameters such as snow depth, sea level, and vegetation height.

Keywords

Multi-GNSS , Multipath , GNSS-IR , SNR , Smartphone

Ethical Statement

This study has been supported by the Scientific and Technological Research Council of Türkiye (TÜBİTAK) within the scope of the Research Support Projects Directorate (ARDEB) under project number 121Y348.

Supporting Institution

TÜBİTAK

Project Number

121Y348

Thanks

This study was conducted as part of the doctoral thesis being prepared by the first author at Yildiz Technical University, Graduate School of Science and Engineering, Department of Geomatic Engineering, and has been supported by the Scientific and Technological Research Council of Türkiye (TÜBİTAK) within the scope of the Research Support Projects Directorate (ARDEB) under project number 121Y348.

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