GPS-R L1 interference signal processing for soil moisture estimation: an experimental study

Abstract

Global positioning system reflectometry (GPS-R) is an emerging area of GPS applications in microwave remote sensing using multipath reflected signals. Soil moisture estimation is one of the many potential applications of the GPS-R technique. The focus of this study is on investigating the feasibility of soil moisture estimation based on GPS L1 band interference signals which can be readily captured using a low-cost off-the-shelf L1-band GPS receiver. The theoretical background is studied, and the field experiments conducted are described. Power spectrum analysis is performed on the received interference signals to determine the interference signal frequency variation, and cosine similarity is applied to identify the initial phase change. Data collected at a number of continuously operating GPS stations are also analyzed. The results demonstrate that both interference signal frequency and phase have changed significantly after rainfalls occurred. That is, it is possible to estimate soil moisture by analyzing the frequency change and phase shift. However, it is also observed that the phase shift is inconsistent in some cases. Ongoing work will focus on figuring out the source of the inconsistency so that reliable estimation of soil moisture can be achieved.

Soil Moisture Estimation Based on GNSS-R Signal

“…One is the penetration depth, which is defined as the depth below the surface at which 1/e of the surface power density of a perpendicularly incident wave remains in a half-space of the material at a sp type of depth is the 'moisture sensing depth' which is defined as the effective reflection depth of approximately one a wavelength in the medium for passive microwave remote sensing. Though the 'moisture sensing depth' validate experimentally, it is consistent with experimental results [12]. Here, ∆h is used to represent the sensing depth, as GNSS-R system.…”

Estimativa da Umidade do Solo por Refletometria GNSS: uma Revisão Conceitual

“…In Chew et al (2015) an algorithm was developed that started to consider the effects of vegetation on modeling. Yan et al (2014) conducted research using a low-cost GPS receiver with frequency L1. Yan et al (2016) used the B1 (BeiDou) and L1 (GPS) modulations with SNR obtained via NMEA 0138 sentence.…”

Using the BDS-R Signal for Soil Moisture Estimation

“…GNSS-R can been used to sense SM [4], ocean altimetry, and ice properties [5,6]. Some experiments have been conducted by employing GPS-R signals [7].…”