Abstract
Change of globe surface height is an important factor to study human living environment. The Geoscience Laser Altimeter System (GLAS) on ICESat is the first laser-ranging instrument for continuous global observations of the Earth. In order to have a comprehensive understanding of full-waveform laser altimeter, this study simulated the operating mode of ICESat and modeled different terrains’ (platform terrain, slope terrain, and artificial terrain) echo waveforms based on the radar equation. By changing the characteristics of the system and the targets, numerical echo waveforms can be achieved. Hereafter, we mainly discussed the factors affecting the amplitude and size (width) of the echoes. The experimental results implied that the slope of the terrain, backscattering coefficient and reflectivity, target height, target position in the footprint and area reacted with the pulse all can affect the energy distribution of the echo waveform and the receiving time. Finally, Gaussian decomposition is utilized to decompose the echo waveform. From the experiment, it can be noted that the factors which can affect the echo waveform and by this way we can know more about large footprint full-waveform satellite laser altimeter.
Highlights
For the reason that the measurement of altimeter can provide high precision elevation or distance information, it can record the complete waveform of the backscattered signal echo, especially for the full-waveform laser altimeter (Mallet, 2009)
This paper mainly focuses on the factors affecting the echo waveform, especially for the width and amplitude of the waveform, based on simulation of different terrain surfaces and transmitted pulse parameters
I is the serial number of targets; N is total number of targets; PR,i (t) is the energy of target i echo waveform at time t ; PT (t) is the energy of the emitted pulse at time t ; t is beam width of transmitted pulse; i is the reflectivity of target i ; As,i is the area irradiated by the pulse energy; Ri is the distance between target i and transmitter; i is the backscattering angle of the target; DR is the diameter of the receiving antenna aperture; atm is the atmospheric influence to signal; sys is the systemic influence to signal; a and b is the footprint elliptical semi-major axis and semi-minor axis, This contribution has been peer-reviewed. doi:10.5194/isprsarchives-XLI-B1-47-2016
Summary
Laser altimeters placed on different platforms (airborne, satellite) have been widely used in lots of areas like mass balance estimation in Antarctica, vegetation vertical structure, long trend monitor of sea level and so on (Anderson et al, 2005; Alexander et al, 2010; Garvin et al, 1998; Gong et al, 2011; Hyyppäet al., 2001; Joerg, et al, 2015; Means and Acker, 1999; Næsset and Bjerknes, 2001; Nilsson, 1996; Smith et al, 1998; Tian et al.,2015). For the reason that the measurement of altimeter can provide high precision elevation or distance information, it can record the complete waveform of the backscattered signal echo, especially for the full-waveform laser altimeter (Mallet, 2009). A good example is the instrument Geoscience Laser Altimeter System (GLAS) placed on the Ice, Cloud and Land Elevation Satellite (ICESat) launched by NASA in 2003. The GLAS instrument records the signal from the entire time-of-flight of the 1064nm pulse to range from the spacecraft to the target. This paper mainly focuses on the factors affecting the echo waveform, especially for the width and amplitude of the waveform, based on simulation of different terrain surfaces and transmitted pulse parameters
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