22 October 2010 Time information extraction of return signal for laser altimeter over ladder terrain
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Laser altimetry is a new measurement technique. Altimeter receives the return signals after launching laser pulses to the ground. Three-dimensional information on the ground is obtained by analyzing the corresponding relationship between return signal features and topographical features. But there is an apparent deficiency when using the data points to establish the three-dimensional DSM. That is the accurate time information of the return signal cannot be obtained when positioning the edge lines of the ladder terrain. In this article, the distribution of the echo waveform over the ladder terrain of city buildings is simulated by a self-designed altimeter waveform simulator under different direction angles and parameters of the terrain. The best extraction method of the return time information at the edge line is identified by analyzing the waveform characteristics at the edge line of this terrain, which enhances the accuracy of applications of the ladder terrain modeling. The time information of the return signal is extracted under various parameters by applying five methods which are accepted internationally, namely Peak point, Mean point, 50% Rise time point, Center of Area point, and Midpoint. Then the experiment values are compared to the actual values. According to the results of the simulations, the difference between the experiment value of the 50% Rise time point and the actual value is minimal. Its resolution ratio is about ten time units maintaining in a narrow range. It proves that this method can effectively improve the accuracy of the extracted time information of the return signal at the edge line over ladder terrain. And it provides a valid data source for establishing a more accurate DSM model.
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Wei Zhong, Wei Zhong, Xu Feng, Xu Feng, Guohui Wu, Guohui Wu, Hui Zhou, Hui Zhou, } "Time information extraction of return signal for laser altimeter over ladder terrain", Proc. SPIE 7658, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology, 76581B (22 October 2010); doi: 10.1117/12.864173; https://doi.org/10.1117/12.864173

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