A METHOD USING GNSS LH-REFLECTED SIGNALS FOR SOIL ROUGHNESS ESTIMATION
Keywords: GNSS-R, Roughness model, Reflectivity, Surface roughness, Soil moisture, Bare soil
Abstract. Global Navigation Satellite System Reflectometry (GNSS-R) is based on the concept of receiving GPS signals reflected by the ground using a passive receiver. The receiver can be on the ground or installed on a small aircraft or UAV and collects the electromagnetic field scattered from the surface of the Earth. The received signals are then analyzed to determine the characteristics of the surface. Many research has been reported showing the capability of the GNSS-R technique. However, the roughness of the surface impacts the phase and amplitude of the received signals, which is still a worthwhile study. This paper presented a method can be used by GNSS-R to estimate the surface roughness. First, the data was calculated in the specular reflection with the assumption of a flat surface with different permittivity. Since the power reflectivity can be evaluated as the ratio of left-hand (LH) reflected signal to the direct right-hand (RH) signal. Then a semi-empirical roughness model was applied to the data for testing. The results showed the method can distinguish the water and the soil surface. The sensitivity of the parameters was also analyzed. It indicates this method for soil roughness estimation can be used by GNSS-R LH reflected signals. In the next step, several experiments need to be done for improving the model and exploring the way of the estimation.
"Kuna njia ya kutumia ishara za GNSS ""LH"" kwa makadirio ya ukali wa udongo, ambayo ni pamoja na: GNSS-R, mfano wa ukali, mwangaza, ukali wa uso, unyevu wa udongo, udongo wa wazi." Global Navigation Satellite System Reflectometry (GNSSR) ni mfumo wa kupokea ishara za GPS kutoka kwa ardhi kwa kutumia kipaza sauti. Mpokeaji anaweza kuwa chini au imewekwa kwenye ndege ndogo au UAV na hukusanya uwanja wa umeme uliosambazwa kutoka uso wa Dunia. Ishara zilizopokelewa kisha kuchambuliwa kuamua sifa ya uso. Utafiti mwingi umeripotiwa kuonyesha uwezo wa mbinu ya GNSS-R. Hata hivyo, ukali wa uso huathiri awamu na amplitude ya ishara zilizopokelewa, ambayo bado ni utafiti wenye thamani. Karatasi hii iliyotolewa mbinu inaweza kutumika na GNSS-R kukadiria roughness uso. Kwanza, data ilihesabiwa katika tafakari ya kioo kwa dhana ya uso wa gorofa na permittivity tofauti. Kwa kuwa nguvu reflectivity inaweza kutathminiwa kama uwiano wa kushoto-mkono (LH) kutafakari ishara kwa moja kwa moja kulia-mkono (RH) ishara. Kisha nusu-empirical roughness mfano ilitumiwa kwa data kwa ajili ya kupima. Matokeo yalionyesha mbinu hiyo inaweza kutofautisha maji na uso wa udongo. Uwezo wa vigezo pia ulichunguzwa. Kwa mfano, kuna uwezekano wa kuonekana kwa njia ya GNSS-RH, ambayo inaweza kuonekana kwa njia ya GNSS-RH. Katika hatua inayofuata, majaribio kadhaa yanahitaji kufanywa kwa kuboresha mfano na kuchunguza njia ya makadirio.