||Echo Detection and Land Cover Classification of Airborne Waveform LiDAR Data
||Department of Geomatics
Land cover classification
Compared with discrete LiDAR systems, state-of-the-art airborne waveform LiDAR systems provide richer information on illuminated surfaces. Waveform data contains both the spatial and physical information of the surfaces. The geospatial surfaces can be located by detecting the reflected laser signal stored in the waveform with the information of the laser travelling path. The process to detect the reflected signal is known as echo detection. The physical characteristics of surfaces such as the reflectance or surface roughness will deform the shape of the transmitting laser pulse resulting in different waveform features. Such features can be used for land cover classification. For waveform information extraction, the echoes are usually detected before the waveform features are extracted for further analysis. For echo detection, conventional discrete LiDAR systems often use an on-the-fly process to detect points. This process usually misdetects weak or overlapping echoes, thus resulting in poor geometry when the structure of a scanned area is complex, such as a forest area. This study proposes an echo detection approach based on wavelet transformation that is capable of detecting weak returns and resolving overlapping echoes. Simulated and real waveform datasets of a forest area were both used in this study. The simulated waveform data were utilized to compare the proposed detector with two other popular detectors, namely, zero crossing (ZC) and Gaussian decomposition (GD), in terms of their ability to deal with weak or overlapping echoes. The real waveform dataset were used to demonstrate the wavelet-based (WB) algorithm for exploring missing echoes. Experiments using simulated data showed that the WB and GD detectors are superior to the ZC detector in finding overlapping echoes. The WB algorithm performs well when dealing with overlapping echoes with low signal-to-noise ratio. The proposed WB algorithm was then applied to the real waveform dataset to test its effectiveness in detecting missing echoes. Results show that the WB algorithm can find more than 31.5% number of points than that of the used LiDAR system. An automatic filtering process was applied to the point clouds extracted from the waveform data to classify the ground points. This paper presents assessment methods based on the visual analyses of point classification and on the elevation difference of generated digital elevation models. Results show that the filtering accuracy and the accuracy of the digital elevation model are both improved because an enhanced geometry of the landscape can be obtained from the detected points. For land cover classification, features that can be derived from waveform data to describe land covers are divided into two categories, namely, echo-based and waveform-based features. Echo-based features have been widely used by previous studies to effectively classify land covers when the waveform has a single return. When the waveform contains multi-returns, echo-based features would fail to distinguish some land covers. Thus, waveform-based features are used and investigated in this study to complement the disadvantages of echo-based features. Experiments show that land cover classification can be improved with the integration of echo-based and waveform-based features.
摘 要 I
LIST OF TABLES VIII
LIST OF FIGURES IX
LIST OF ACRONYMS XIV
Chapter 1: Introduction 1
1.1 Background 1
1.1.1 Digital elevation model and land covers 1
1.1.2 Airborne LiDAR remote sensing 2
1.2 Research motivation 3
1.2.1 Discrete-return airborne LiDAR system 3
1.2.2 Full-waveform airborne LiDAR system 4
1.3 Research objective 5
1.3.1 Proposition of a wavelet-based detector 5
1.3.2 The use of points detected from waveform data for DEM generation 6
1.3.3 The use of waveform features for land cover classification 7
1.3.4 Summary 8
1.4 Dissertation structure 9
CHAPTER 2: TOPOGRAPHIC AIRBORNE WAVEFORM LIDAR SYSTEM 10
2.1 Laser 10
2.2 Principle of laser ranging 11
2.3 Laser scanning 12
2.4 Principle of point positioning 14
2.5 Waveform LiDAR system 16
2.5.1 Digitization of waveform 17
2.5.2 Waveform modeling 18
2.5.3 Waveform simulation 20
2.5.4 Influences of target properties on waveforms 21
2.6 Summary 29
CHAPTER 3: WAVELET-BASED ECHO DETECTOR 30
3.1 Introduction 30
3.2 Review of echo detectors 31
3.2.1 Zero-crossing method 31
3.2.2 Gaussian decomposition algorithm 32
3.3 Wavelet-based echo detector 33
3.4 Noise estimation 37
3.5 Procedure of detecting echoes 38
3.6 SNR of echoes 40
3.7 Test of the weak echo detection 40
3.8 Test of overlapping echo detection 41
3.9 Experimental results and discussions 44
3.9.1 Test Results of Weak Echo Detection 44
3.9.2 Test Results of Overlapping Echo Detection 45
3.10 Summary 49
CHAPTER 4: WAVEFORM POINT CLOUD EXTRACTION AND FILTERING 50
4.1 Introduction 50
4.2 Test area and real waveform data 51
4.3 Point cloud extraction from waveform data 55
4.4 Point cloud filtering 55
4.5 EXPERIMENTS 57
4.5.1 Results of ground point filtering 57
4.5.2 Ground point density on DEM accuracy 66
CHAPTER 5: WAVEFORM CLASSIFICATION FOR LAND COVER IDENTIFICATION 71
5.1 Introduction 71
5.2 Methodology 72
5.3 Waveform decomposition 74
5.4 Feature generation 75
5.4.1 Echo-based features 75
5.4.2 Waveform-based features 76
5.5 Experiments and results 79
5.5.1 Study area and the land cover classes 79
5.5.2 Feature analysis 81
5.5.3 Classification accuracy 91
CHAPTER 6: CONCLUSION 103
6.1 Concluding remarks 103
6.2 Research contribution and originality 105
6.3 Research limitations and assumptions 105
6.4 Recommendations for future work 106
Alexander, C., Tansey, K., Kaduk, J., Holland, D., and Tate, N. J. "Backscatter coefficient as an attribute for the classification of full-waveform airborne laser scanning data in urban areas," ISPRS Journal of Photogrammetry and Remote Sensing, 65(5), 423-432, 2010.
Anderson, J., Martin, M. E., Smith, M. L., Dubayah, R. O., Hofton, M. A., Hyde, P., et al. "The use of waveform lidar to measure northern temperate mixed conifer and deciduous forest structure in New Hampshire," Remote Sensing of Environment, 105(3), 248-261, 2006.
Antonarakis, A. S., Richards, K. S., and Brasington, J. "Object-based land cover classification using airborne LiDAR," Remote Sensing of Environment, 112(6), 2988-2998, 2008.
Axelsson, P. "DEM generation from laser scanner data using adaptive TIN models," International Archives of Photogrammetry and Remote Sensing, 33(B4/1), 110-117, 2000.
Baltsavias, E. P. "A comparison between photogrammetry and laser scanning," ISPRS Journal of Photogrammetry and Remote Sensing, 54(2-3), 83-94, 1999.
Barbara, K. "Status and future of laser scanning, synthetic aperture radar and hyperspectral remote sensing data for forest biomass assessment," ISPRS Journal of Photogrammetry and Remote Sensing, 65(6), 581-590, 2010.
Brennan, R. L., and Prediger, D. J. "Coefficient kappa: Some uses, misuses, and alternatives," Educational and psychological measurement, 41(3), 687-699, 1981.
Bretar, F., Chauve, A., Bailly, J. S., Mallet, C., and Jacome, A. "Terrain surfaces and 3-D landcover classification from small footprint full-waveform lidar data: application to badlands," Hydrol. Earth Syst. Sci., 13(8), 1531-1544, 2009.
Brunel, C., Certain, R., Sabatier, F., Robin, N., Barusseau, J. P., Aleman, N., et al. "20th century sediment budget trends on the Western Gulf of Lions shoreface (France): An application of an integrated method for the study of sediment coastal reservoirs," Geomorphology, 204, 625-637, 2014.
Campbell, J. B. Introduction to Remote Sensing: Taylor & Francis. 2002.
Chang, L.-D., Slatton, K. C., and Krekeler, C. "Bare-earth extraction from airborne LiDAR data based on segmentation modeling and iterative surface corrections," Journal of Applied Remote Sensing, 4(1), 041884-041884-041830, 2010.
Chao, W.-C. The Composition and Spatial Pattern of Nanjenshan Lowland Rain Forests. doctoral dissertation, National Taiwan University, 2008.
Chauve, A., Vega, C., Durrieu, S., Bretar, F., Allouis, T., Deseilligny, M. P., et al. "Advanced full-waveform lidar data echo detection: Assessing quality of derived terrain and tree height models in an alpine coniferous forest," International Journal of Remote Sensing, 30(19), 5211-5228, 2009.
Cheng, Z., Pellettiere, J. A., and Pilkey, W. D. (2006). Energy Distribution Analysis of Impact Signals Based on Wavelet Decompositions: DTIC Document.
Choi, E., and Lee, C. "Feature extraction based on the Bhattacharyya distance," Pattern Recognition, 36(8), 1703-1709, 2003.
Cobby, D. M., Mason, D. C., and Davenport, I. J. "Image processing of airborne scanning laser altimetry data for improved river flood modelling," ISPRS Journal of Photogrammetry and Remote Sensing, 56(2), 121-138, 2001.
Collin, A., Long, B., and Archambault, P. "Benthic Classifications Using Bathymetric LIDAR Waveforms and Integration of Local Spatial Statistics and Textural Features," Journal of Coastal Research, 86-98, 2011.
Congalton, R. G. "A review of assessing the accuracy of classifications of remotely sensed data," Remote Sensing of Environment, 37(1), 35-46, 1991.
Croke, J., Todd, P., Thompson, C., Watson, F., Denham, R., and Khanal, G. "The use of multi temporal LiDAR to assess basin-scale erosion and deposition following the catastrophic January 2011 Lockyer flood, SE Queensland, Australia," Geomorphology, 184(0), 111-126, 2013.
Doneus, M., Briese, C., Fera, M., and Janner, M. "Archaeological prospection of forested areas using full-waveform airborne laser scanning," Journal of Archaeological Science, 35(4), 882-893, 2008.
Dubayah, R. O., and Drake, J. B. "Lidar Remote Sensing for Forestry," Journal of Forestry, 98(6), 44-46, 2000.
Estornell, J., Ruiz, L. A., Velázquez-Martí, B., and Fernández-Sarría, A. "Estimation of shrub biomass by airborne LiDAR data in small forest stands," Forest Ecology and Management, 262(9), 1697-1703, 2011.
Fieber, K. D., Davenport, I. J., Ferryman, J. M., Gurney, R. J., Walker, J. P., and Hacker, J. M. "Analysis of full-waveform LiDAR data for classification of an orange orchard scene," ISPRS Journal of Photogrammetry and Remote Sensing, 82, 63-82, 2013.
Foody, G. M. "Status of land cover classification accuracy assessment," Remote Sensing of Environment, 80(1), 185-201, 2002.
Friedrich, A. "Airborne laser scanning—present status and future expectations," ISPRS Journal of Photogrammetry and Remote Sensing, 54(2–3), 64-67, 1999.
González-Olabarria, J.-R., Rodríguez, F., Fernández-Landa, A., and Mola-Yudego, B. "Mapping fire risk in the Model Forest of Urbión (Spain) based on airborne LiDAR measurements," Forest Ecology and Management, 282, 149-156, 2012.
Guggenmoos-Holzmann, I. "The meaning of kappa: Probabilistic concepts of reliability and validity revisited," Journal of Clinical Epidemiology, 49(7), 775-782, 1996.
Hollaus, M., Aubrecht, C., Höfle, B., Steinnocher, K., and Wagner, W. "Roughness Mapping on Various Vertical Scales Based on Full-Waveform Airborne Laser Scanning Data," Remote Sensing, 3(3), 503-523, 2011.
Huang, Ching, Y., Hou, and Ping-Chun Lucy, G., "Density and diversity of litter amphibians in a monsoon forest of southern Taiwan," (Vol. 43, pp. 8). Taipei, TAIWAN, PROVINCE DE CHINE: Academia Sinica. 2004.
Huang, W., Sun, G., Dubayah, R., Cook, B., Montesano, P., Ni, W., et al. "Mapping biomass change after forest disturbance: Applying LiDAR footprint-derived models at key map scales," Remote Sensing of Environment, 134(0), 319-332, 2013.
Irish, J. L., and White, T. E. "Coastal engineering applications of high-resolution lidar bathymetry," Coastal Engineering, 35(1–2), 47-71, 1998.
Jelalian, A. V. Laser Radar Systems: Books on Demand. 1992.
Jiao, L., Gao, S., Zhang, F., and Li, H. "Quantification of components in overlapping peaks from capillary electrophoresis by using continues wavelet transform method," Talanta, 75(4), 1061-1067, 2008.
Kwan, M.-P., and Ransberger, D. M. "LiDAR assisted emergency response: Detection of transport network obstructions caused by major disasters," Computers, Environment and Urban Systems, 34(3), 179-188, 2010.
Landgrebe, D., and Biehl, L. An introduction to MultiSpec: Purdue Research Foundation, West Lafayette, Indiana. 1997.
Lin, Y.-C., Mills, J. P., and Smith-Voysey, S. "Rigorous pulse detection from full-waveform airborne laser scanning data," International Journal of Remote Sensing, 31(5), 1303-1324, 2010a.
Lin, Y. C.. Digital Terrain Modelling from Small-footprint, Full-waveform Airborne Laser Scanning Data, doctoral dissertation, School of Civil Engineering and Geosciences, University of Newcastle UK. 2010b.
Liu, C., Shi, B., Yang, X., Li, N., and Wu, H. "Automatic Buildings Extraction From LiDAR Data in Urban Area by Neural Oscillator Network of Visual Cortex," Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, 6(4), 2008-2019, 2013.
Liu, X. "Airborne LiDAR for DEM generation: some critical issues," Progress in Physical Geography, 32(1), 31-49, 2008.
Mallat, S. A Wavelet Tour of Signal Processing, Third Edition: The Sparse Way: Academic Press. 2008.
Mallet, C., and Bretar, F. "Full-waveform topographic lidar: State-of-the-art," ISPRS Journal of Photogrammetry and Remote Sensing, 64(1), 1-16, 2009.
Meng, X., Wang, L., Silván-Cárdenas, J. L., and Currit, N. "A multi-directional ground filtering algorithm for airborne LIDAR," ISPRS Journal of Photogrammetry and Remote Sensing, 64(1), 117-124, 2009.
Mongus, D., and Žalik, B. "Parameter-free ground filtering of LiDAR data for automatic DTM generation," ISPRS Journal of Photogrammetry and Remote Sensing, 67, 1-12, 2012.
Morsdorf, F., Frey, O., Koetz, B., and Meier, E. Ray Tracing for Modeling of Small Footprint Airborne Laser Scanning Returns. Paper presented at the Proc. ISPRS Workshop ``Laser Scanning 2007 and SilviLaser 2007, 2007.
Morsdorf, F., Nichol, C., Malthus, T., and Woodhouse, I. H. "Assessing forest structural and physiological information content of multi-spectral LiDAR waveforms by radiative transfer modelling," Remote Sensing of Environment, 113(10), 2152-2163, 2009.
Murat, Y. S. "An Entropy (Shannon) based Traffic Safety Level Determination Approach for Black Spots," Procedia - Social and Behavioral Sciences, 20, 786-795, 2011.
Neuenschwander, A. L., Magruder, L. A., and Tyler, M. "Landcover classification of small-footprint, full-waveform lidar data," Journal of Applied Remote Sensing, 3, 2009.
Pfeifer, N., and Mandlburger, G. "LiDAR data filtering and DTM generation.” In: Shan, J., Toth, C.K. (Eds.), Topographic Laser Ranging and Scanning: Principles amd Processing, Taylor & Francis Group, London, 307-333, 2009.
Pingel, T. J., Clarke, K. C., and McBride, W. A. "An improved simple morphological filter for the terrain classification of airborne LIDAR data," ISPRS Journal of Photogrammetry and Remote Sensing, 77(0), 21-30, 2013.
Reitberger, J., Krzystek, P., and Stilla, U. "Benefit of airborne full waveform lidar for 3D segmentation and classification of single trees," ASPRS 2009 Annual Conference. Baltimal, MD, United States. March 9-13, 2009, 1-9, 2009.
Shan, J., and Toth, C. K. Topographic laser ranging and scanning: principles and processing: CRC Press. 2009.
Shao, X., Cai, W., and Sun, P. "Determination of the component number in overlapping multicomponent chromatogram using wavelet transform," Chemometrics and Intelligent Laboratory Systems, 43(1-2), 147-155, 1998.
Silván-Cárdenas, J. L., and Wang, L. "A multi-resolution approach for filtering LiDAR altimetry data," ISPRS Journal of Photogrammetry and Remote Sensing, 61(1), 11-22, 2006.
Stilla, U., and Jutzi, B. "Waveform analysis of small-footprint pulsed laser systems. In: Shan, J., Toth, C.K. (Eds.), Topographic Laser Ranging and Scanning: Principles amd Processing, Taylor & Francis Group, London, 215-234," 2009.
Varhola, A., and Coops, N. C. "Estimation of watershed-level distributed forest structure metrics relevant to hydrologic modeling using LiDAR and Landsat," Journal of Hydrology, 487, 70-86, 2013.
Ventura, G., Vilardo, G., Terranova, C., and Sessa, E. B. "Tracking and evolution of complex active landslides by multi-temporal airborne LiDAR data: The Montaguto landslide (Southern Italy)," Remote Sensing of Environment, 115(12), 3237-3248, 2011.
Wagner, W., Hollaus, M., Briese, C., and Ducic, V. "3D vegetation mapping using small-footprint full-waveform airborne laser scanners," International Journal of Remote Sensing, 29(5), 1433 - 1452, 2008.
Wagner, W., Ullrich, A., Ducic, V., Melzer, T., and Studnicka, N. "Gaussian decomposition and calibration of a novel small-footprint full-waveform digitising airborne laser scanner," ISPRS Journal of Photogrammetry and Remote Sensing, 60(2), 100-112, 2006.
Wagner, W., Ullrich, A., Melzer, T., Briese, C., and Kraus, K. From single-pulse to full-waveform airborne laser scanners: potential and practical challenges Paper presented at the The International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 2004.
Wang, C.-K., and Tseng, Y.-H. "Dual-directional profile filter for digital terrain model generation from airborne laser scanning data," Journal of Applied Remote Sensing, 8(1), 083619-083619, 2014.
Wang, C., Tang, F. X., Li, L. W., Li, G. C., Cheng, F., and Xi, X. H. "Wavelet Analysis for ICESat/GLAS Waveform Decomposition and Its Application in Average Tree Height Estimation," IEEE Geoscience and Remote Sensing Letters, 10(1), 115-119, 2013.
Warrens, M. J. "Cohen’s kappa is a weighted average," Statistical Methodology, 8(6), 473-484, 2011.
Wehr, A., and Lohr, U. "Airborne laser scanning--an introduction and overview," ISPRS Journal of Photogrammetry and Remote Sensing, 54(2-3), 68-82, 1999.
Wu, J. Y., van Aardt, J. A. N., and Asner, G. P. "A Comparison of Signal Deconvolution Algorithms Based on Small-Footprint LiDAR Waveform Simulation," IEEE Transactions on Geoscience and Remote Sensing, 49(6), 2402-2414, 2011.
Yan, W. Y., Shaker, A., and El-Ashmawy, N. "Urban land cover classification using airborne LiDAR data: A review," Remote Sensing of Environment, 158(0), 295-310, 2015.
Zhao, K., and Popescu, S. "Lidar-based mapping of leaf area index and its use for validating GLOBCARBON satellite LAI product in a temperate forest of the southern USA," Remote Sensing of Environment, 113(8), 1628-1645, 2009.