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Open AccessArticle

A Fast, Three-Dimensional, Indirect Geolocation Method Using IAGM and DSM Data without GCPs for Spaceborne SAR Images

by Min Liu * and Peng Xiao
Department of Applied Science and Frontier Technology, Qian Xuesen Laboratory of Space Technology, Beijing 100094, China
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(23), 5062; https://doi.org/10.3390/s19235062
Received: 12 October 2019 / Revised: 5 November 2019 / Accepted: 18 November 2019 / Published: 20 November 2019
(This article belongs to the Section Remote Sensors)
To determine the geolocation of a pixel for spaceborne synthetic aperture radar (SAR) images, traditional indirect geolocation methods can cause great computational complexity. In this paper, a fast, three-dimensional, indirect geolocation method without ground control points (GCPs) is presented. First, the Range-Doppler (RD) geolocation model with all the equations in the Earth-centered rotating (ECR) coordinate system is introduced. By using an iterative analytical geolocation method (IAGM), the corner point locations of a quadrangle SAR image on the Earth’s surface are obtained. Then, a three-dimensional (3D) grid can be built by utilizing the digital surface model (DSM) data in this quadrangle. Through the proportional relationship for every pixel in the 3D grid, the azimuth time can be estimated, which is the key to decreasing the calculation time of the Doppler centroid. The results show that the proposed method is about 12 times faster than the traditional method, and that it maintains geolocation accuracy. After acquiring the precise azimuth time, it is easy to obtain the range location. Therefore, the spaceborne SAR image can be geolocated to the Earth surface precisely based on the high-resolution DSM data. View Full-Text
Keywords: spaceborne synthetic aperture radar (SAR); indirect geolocation; Earth centered rotating (ECR) coordinate system; iterative analytical geolocation method (IAGM); digital surface model (DSM) spaceborne synthetic aperture radar (SAR); indirect geolocation; Earth centered rotating (ECR) coordinate system; iterative analytical geolocation method (IAGM); digital surface model (DSM)
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Liu, M.; Xiao, P. A Fast, Three-Dimensional, Indirect Geolocation Method Using IAGM and DSM Data without GCPs for Spaceborne SAR Images. Sensors 2019, 19, 5062.

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