Research On Detection Of Sea Ice Using GNSS Reflected Signals

The risk of sea ice ocean disasters is greatest in the Polar Regions and certain areas of high latitudes. These areas are all prone to ice disasters that can directly damage the facilities of nearshore port, affect the marine transportation, the marine fishery and the development of offshore oil and gas resources. Traditionally, there are two basic methods used in the large-scale detection of sea ice disasters using remote sensing: the first is based on visible remote sensing, the second is based on microwave remote sensing. The visible remote sensing affected by weather factors, and it cannot detect sea ice conditions in all weather and all day. Microwave remote sensing is capable of imaging under all-weather conditions and all day, and it is very expensive. At present, there should be a new method of detecting sea ice in the large-scale which is low cost in all weather and all day.With the continuous development of Global Navigation Satellite System(GNSS), foreign scientists have found direct signal of GNSS can continuously provide accurate time information, precise location information and accurate navigation information. Traditionally, multipath signal(reflected signal) should be suppressed or eliminated, and the reflected signal carry a large amount of useful physical information on reflected surface. The GNSS reflected signal technology(GNSS-R) can be used in several potential applications: ocean altimetry, ocean wind, soil moisture, dry snow and so on.Since 2000, foreign scientists Komjathy etc. found that GNSS-R technology has potential possibility for detecting sea ice. After continuous research, until 2012, the European space agency scientists Fabra etc. used the data of GPS reflected signals, based the principle of Fresnel reflection coefficient and build the polarization ratio model. At low elevation(5 ° to 15 °), they detect changes in the amount of sea ice using the polarization ratio model.Internal scientists has only just begun using GNSS-R technology to detect sea ice. Until 2013, some scientists began to research of the polarization ratio model to detect sea ice. Internal research is more focused on the feasibility of the polarization ratio model to detect sea ice. There are few sea ice experiments.In both here and abroad, there are rarely sea ice model using GNSS-R technology and the polarization ratio model is limited by low satellite elevation. The paper based the principle of Fresnel reflection coefficient and puts forward the reflected power ratio model for high satellite elevation to detect sea ice. Bohai sea ice experiment using GPS reflected signals is the first experiment in China to detecting sea ice using GPS reflected signals technology(GPS-R), and Bohai sea ice experiment using BeiDou reflected signals technology(Bei Dou-R) is the first experiment to detecting sea ice using BeiDou-R all over the world. By analyzing of experimental results, the paper verified that the reflected power ratio of sea water is significantly greater than the reflected power ratio of sea ice, the reliability of the reflected power ratio model suited high satellite elevation. The paper expanded the application range of BeiDou system.The main contents of this paper are as follows:1. Firstly, the paper introduces the background and significance of sea icedetecting. Secondly, the paper analyses the deficiency of traditional remotesensing technology in sea ice detecting. Then, the paper summarizes the currentstates of GNSS-R technology at home and abroad. On this basis, the paperanalyses the existing problems of the polarization ratio model.2. The paper introduces the characteristic of electromagnetic wave to detectingsea ice and the polarization properties(left-handed and right-handed). Then,the paper introduces the geometric relations of GNSS-R, the principle ofFresnel reflection coefficient and the sea ice detection data processing. Basedthe principle of Fresnel reflection coefficient, the paper puts forward thereflected power ratio model to detecting sea ice by calculating the Fresnelreflection coefficient of Bohai Sea. Finally, the paper compares with thetraditional polarization ratio model, the reflected power ratio model is morestable for high satellite elevation. 3. In 2013 and 2015, the paper conducts the Bohai independent shore-basedexperiments respectively using GPS-R technology and BeiDou-R technology.By analyzing of experimental results, the paper contrasts the reflected powerratio of sea water and sea ice, detects the change of sea ice trend(freezing/melting), and the feasibility of the reflected power ratio model. Thepaper sets up a good foundation of detecting sea ice concentrationquantitatively in the future and provides a new method of the sea ice disasterwarning.