Evaluation and Correction of Elevation Angle Influence for Coastal GNSS-R Ocean Altimetry

Abstract

The elevation angle influence on coastal GNSS-R ocean code-based altimetry for GPS signals (L1 C/A and L5) and BDS B1 signals is investigated, and the corresponding correction method is presented. The study first focuses on the coastal ocean altimetry method, including the general experiment geometry and the code delay estimation using the single-point tracking algorithm. The peak power and the maximum first derivative are used as the location of the specular point. Then, the sensitivity of the height retrieved using the above coastal ocean altimetry method to elevation angle is analyzed based on the Z-V model. It can be seen that the elevation angle has a significant influence on the height retrieval, which will affect the precision of the coastal GNSS-R ocean altimetry. Finally, two correction methods, the model-driven method and the data-driven method, are proposed. The coastal altimetry experiments demonstrate that the correction methods can correct the elevation angle influence, and the data-driven method is more effective. The experimental results show that, after correcting the elevation angle influence, the code-based altimetry precision of the GPS L1 C/A signal, L5 signal, and BDS B1 signal can be up to the meter level, decimeter level (less than 4 decimeters), and meter level with respect to a reference tide gauge (TG) data set, respectively, without smoothing over time. These results provide information to guide the sea surface height retrieval using coastal GNSS-R, especially multi-satellite observation and GNSS signal with a higher chipping rate.

Analysis of GNSS-R Code-Level Altimetry Using QZSS C/A, L1C, and BDS B1C Signals and Their Combinations in a Coastal Experiment

“…One is the peak point of the waveform; the other is the peak point of the derivative waveform [35]. In [36], it was found that the peak of the waveform can provide better performance than the peak of derivative waveform. Therefore, we used the peak of the waveform as the arrival of the reflected signal.…”

Enhancing the Accuracy of GNSS-IR Sea Surface Height Retrieval with a Novel Deep-learning Composite Atmospheric Delay Correction Inversion Model

“…The sea surface height (SSH) is a key parameter in marine research and contributes signi cantly to the development of high-precision ocean gravity elds and the detection of changes in the dynamic environment of the ocean (Li et al 2020;Li et al 2014; Zhang et al 2021). SSH can be categorized into nearshore and oceanic types, each requiring different monitoring strategies due to their distinct geographic characteristics (Antony et al 2002).…”

“…Many researchers utilize Global Navigation Satellite System (GNSS) re ection signals to observe SSH changes due to continuous GNSS development. Numerous studies exist (Song et al 2020; Zhang et al 2021;Zhu et al 2023). In 2000, Anderson used traditional geodetic GNSS receivers to establish an interferometric model from signal-to-noise ratio (SNR) observations.…”

Advancing Sea Surface Height Retrieval through Global Navigation Satellite System Reflectometry: A Model Interaction Approach with Cyclone Global Navigation Satellite System and FengYun-3E Measurements

“…The leading edge derivatives (LEDs) of spaceborne GNSS-R waveforms are employed and enhanced to retrieve sea surface height in [36]. A correction method is introduced for satellite altitude angles in the detection of sea surface height in [37]. The authors employ model-driven and data-driven methodologies in this study to improve the effects of elevation angle.…”