Abstract
Slope and roughness are basic geophysical properties of terrain surface, and also sources of error in satellite laser altimetry systems. The full-waveform satellite laser altimeter records the complete echo waveform backscattered from the target surface worldwide, so it may be used for both range measurement and inversion analysis of geometric parameters of the target surface. This paper proposes a new method for inversion of slope and roughness of the bare or near-bare terrain within laser footprint using full-waveform satellite laser altimeter data, Shuttle Radar Topographic Mission (SRTM) and topographic prior knowledge. To solve the non-uniqueness of the solution to the inversion problem, this paper used the SRTM and airborne Light Detection and Ranging (LiDAR) data in North Rhine-Westphalia, Germany, to establish a priori hypothesis about real information of topographic parameters. Then, under the constraints of prior hypothesis, the theoretical formulas and rules for slope and roughness inversion using the pulse-width broadening knowledge of satellite laser altimeter echo full-waveform were developed. Finally, based on the full-waveform data from the Geoscience Laser Altimeter System (GLAS) that was borne on ICE, Cloud, and Land Elevation Satellite (ICESat) and SRTM in the West Valley City, Utah and Jackson City, Wyoming, United States of America, the inversion was carried out. The experiment compares the results of proposed method with those of existing ones and evaluates the inversion results using high precision terrain slope and roughness information, which indicates that our proposed method is superior to the state-of-the-art methods, and the inversion accuracy for slope is 0.667° (Mean Absolute Error, MAE) and 1.054° (Root Mean Square Error, RMSE), the inversion accuracy for roughness is 0.171 m (MAE) and 0.250 m (RMSE).
Highlights
Satellite Laser altimeters provide a new and active remote sensing method to obtain the topographic information of Earth, Moon, Mars and other planets from several hundred kilometers [1,2,3,4]
With all the possible data series of slope and roughness of the terrain surface within the laser footprint being calculated using the satellite full-waveform data under the constraints of prior hypothesis of two slope angles of terrain surface, we developed the following rules based on prior knowledge of terrain slope (Figure 7) to determine the final result (Slopeinv, Rqinv ) from terrain parameter inversion sequence using the prior hypothesis of terrain slope (23): Figure 7
February 2006 to February 2008) and Jackson City, Wyoming, United Sates of America (Figure 1c), a total of 311 laser spots from April 2007 to March 2008), 185 laser echo waveforms in West Valley City received from flat land and urban areas and 54 laser echo waveforms in Jackson City received from flat land and mountainous areas, supplemented by the Shuttle Radar Topographic Mission (SRTM) and established prior hypothesis of terrain topographic parameters, were used to invert the terrain slope and roughness using the proposed method
Summary
Satellite Laser altimeters provide a new and active remote sensing method to obtain the topographic information of Earth, Moon, Mars and other planets from several hundred kilometers [1,2,3,4]. By measuring the round-trip flight time of the laser pulse, combined with the position and attitude of satellite platform, the target surface elevation can be determined at decimeter or even centimeter accuracy level [5]. After the satellite laser altimeter emits the laser pulse, several backscattered returns of the target surface can be obtained which contain abundant information of profile elevation, and the exact number of the returns is dependent on the target surface geometry [6]. The full-waveform satellite laser altimeter is able to record the complete waveform of the backscattered signal echo.
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