Abstract
The effect of cloud parallax shift occurs in satellite imaging, particularly for high angles of satellite observations. This study demonstrates new methods of parallax effect correction for clouds observed by geostationary satellites. The analytical method that could be found in literature, namely the Vicente et al./Koenig method, is presented at the beginning. It approximates a cloud position using an ellipsoid with semi-axes increased by the cloud height. The error values of this method reach up to 50 meters. The second method, which is proposed by the author, is an augmented version of the Vicente et al./Koenig approach. With this augmentation, the error can be reduced to centimeters. The third method, also proposed by the author, incorporates geodetic coordinates. It is described as a set of equations that are solved with the numerical method, and its error can be driven to near zero by adjusting the count of iterations. A sample numerical solution procedure with application of the Newton method is presented. Also, a simulation experiment that evaluates the proposed methods is described in the paper. The results of an experiment are described and contrasted with current technology. Currently, operating geostationary Earth Observation (EO) satellite resolutions vary from 0.5 km up to 8 km. The pixel sizes of these satellites are much greater than for maximal error of the least precise method presented in this paper. Therefore, the chosen method will be important when the resolution of geostationary EO satellites reaches 50 m. To validate the parallax correction, procedure data from on-ground radars and the Meteosat Second Generation (MSG) satellite, which describes stormy events, was compared before and after correction. Comparison was performed by correlating the logarithm of the cloud optical thickness (COT) with radar reflectance in dBZ (radar reflectance – Z in logarithmic form).
Highlights
The precision of remote space observations is important when investigating and monitoring various components of global ecological systems, such as marine, forestry, and climate environments [1,2,3,4]
Parallax shift is important for cloud shadow determination, which is a significant issue for solar farms [11] and for flood detection [12]
The coordinates in the above equation were expressed as an angle, expressing them in radians and multiplying by hs allows the result to be calculated in metric units as distances on a sphere of radius hs around a geostationary satellite
Summary
The precision of remote space observations is important when investigating and monitoring various components of global ecological systems, such as marine, forestry, and climate environments [1,2,3,4]. For climate and meteorological investigations, observations of clouds and precipitation on a global scale are usually performed using ground-based radar data and observations from geostationary satellites, due to their high temporal and moderate spatial resolution [7,8,9]. Parallax phenomena have a significant impact on the comparison of data from low-orbit satellites from different sensors [13,14,15,16]. Parallax phenomena have a significant impact on the comparison of data from low-orbit satellites pattern mafrtocmhidnifgfe.reTnht siesnasoprps [r1o3a–1c6h].was suitable for stormy events and other inhomogeneous cloud formations, hoInwteevrmesr oitf umsauthaelmlyatfiacailepdrotbolepmefrofromrmulactionrr, ethcetiopanrailnlaxthsehicftaesfefeoctf fhoromtheoggeeonsteaotiuonsasrpy atial LWP distributiosnat.ellAitensoisthaectruaaltlyteamsppetcipalrcoapseoasmedonbgyst lGowre-oureblilt seatteallli.tesa,nadndRitoies beaesliienrgto[i1n9v,e2s0ti]gauteseddueatosimplified geometric hmigohdeTrehtele,rmewphhoarviacelhbreeaessonslusuetmivoenerasdlaEattaateramtchqputtsiostiotbioseonllvaonecdpaatlhrlyaellfflaixxaestd,hisafatstfewollrietgelelpoaostssaittaiioosnnoa. This method allows the correction error to be reduced to almost zero (assuming Earth to have an ellipsoidal shape)
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