Spaceborne LiDAR Data Full Waveform Processing And Forest Canopy Height Inversion

As an advanced active remote sensing technology,lidar can quickly acquire the three-dimensional information of the target,which has been widely used in various fields of Surveying and mapping.Traditional forest resource survey needs a lot of manpower and material resources,and the survey area is mostly the preset sample plot,which takes a long time.It is difficult to carry out large-scale forest observation,and can not meet the demand of real-time observation of forest vegetation parameters.Spaceborne lidar has the characteristics of high precision,fast speed and strong penetration,which can quickly obtain global forest structure information,thus it has been widely used in forest resource survey and vegetation parameter extraction.In this paper,the development and application of space-borne lidar are summarized.The principle,composition and error correction of the laser altimetry satellite are described.The calculation and processing of the waveform data of space-borne lidar are mainly studied,and the canopy height of forest vegetation is extracted with waveform characteristic parameters.The main contents and work of this paper are as follows:(1)The development history of spaceborne lidar system is summarized,and the application of large spot lidar based on GLAS to extract vegetation canopy height is summarized.The principle of altimetry,composition,orientation,error control and correction of laser altimetry system are briefly discussed.The formulas of coordinate conversion,attitude adjustment,tidal correction and atmospheric correction are deduced.(2)The waveform data processing of the laser altimetry satellite is elaborated in detail,including the research of waveform data conversion,denoising,filtering,fitting and decomposition algorithms;the main waveform characteristic parameters are summarized based on the results of waveform decomposition;the radiation mechanism of the echo data of the laser radar is studied,and the laser pulse from transmitting to receiving is analyzed,and it passes through twice.In the whole process of interaction between atmosphere and ground objects,the lidar equation is deduced Combining with the laser transmission model,the principle and model construction of laser echo simulation are discussed,and the process of surface modeling is emphasized.(3)Laser altimetry waveform data is used to extract forest canopy height.A canopy height estimation model is established based on waveform parameters.The ability of extracting forest vegetation parameters from laser altimetry satellite waveform data is analyzed and verified by field measured data.The waveform parameters extracted from forest echo are greatly affected by terrain.For complex forest terrain,the model parameters are not stable enough.The estimated results are R20.78 and RMSE 2.92.Therefore,this paper refers to a new idea,uses bare ground simulation echo as auxiliary data,and constructs an auxiliary model which is less affected by terrain fluctuation.Finally,the estimated results are R2 0.89 and RMSE 1.21.Finally,GLAS and LandSat-TM are combined to draw the forest canopy height distribution map,and the estimation results are discussed and analyzed.