Extraction of ground surface elevation from ZY-3 winter stereo imagery over deciduous forested areas Wenjian Ni a,b, ⁎, Guoqing Sun b , Kenneth Jon Ranson c , Yong Pang d , Zhiyu Zhang a , Wei Yao e a State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China b Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA c Code 618, Biospheric Sciences Branch, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA d Institute of Forest Resource Information Technique, Chinese Academy of Forestry, Beijing 100091, China e Institute of Photogrammetry and Cartography, Technische Universitaet Muenchen Arcisstr. 21, Munich D-80333, Germany abstract article info Article history: Received 7 August 2014 Received in revised form 12 December 2014 Accepted 14 December 2014 Available online xxxx Keyword: Dense deciduous forest Forest height Ground surface elevation Stereo imagery ZY-3 Photogrammetry Forest height is an important indicator for forest biomass. Ground surface elevation is essential to derive forest height from spaceborne data including interferometric synthetic aperture radar or stereo imagery. Considering the good performance of stereo images in characterizing the vertical structure of forest with non-closed canopies, the main issue addressed in this study is whether stereo imagery acquired in winter can view the ground surface under dense deciduous forest. To make full use of information provided by different observation geometries, the three sets of matching points from different view were combined. Then the vertical distribution of matching points from stereo images was referenced to the vegetation vertical structure and the ground surface elevation from airborne laser scanner (ALS) data. The vertical distribution of matching points from stereo images over typical deciduous forest stands including sparse, disturbed and dense forests were examined. Most matching points were located on the ground surface while some points came from branches and trunks in all the three forest stands. This phenomenon was also observed from a transect of a digital surface model from ZY-3. Twelve elevation indices, including minimum, maximum, mean elevations and an additional nine percentiles of cumulative probability (E10 to E90) from the matching points of ZY-3 over 30 m × 30 m cell were compared with the ground surface elevation from ALS data. The results showed that E30 gave the best measurement of ground surface elevation with R 2 N 0.99 and RMSE = 2.54 m. © 2014 Elsevier Inc. All rights reserved. 1. Introduction The global distribution and structure of terrestrial ecosystems are being rapidly modified by human and natural forces (Rosen et al., 2011). To understand changes and trends in terrestrial ecosystems and the impact of these changes on climate, habitat and biodiversity, it is important to produce high spatial resolution global maps of the three dimensional structure of vegetation and its aboveground biomass (Hall et al., 2011). In the United States of America, the National Aeronau- tics and Space Administration (NASA) once planned to launch the DESDynI mission which was composed with a L-band SAR system and a LiDAR system. One of the main objectives of DESDynI was to charac- terize the global distribution and changes of vegetation aboveground biomass and ecosystem structure related to the global carbon cycle, climate and biodiversity (Rosen et al., 2011). Besides the DESDynI mission, the NASA Carbon Monitoring System (CMS) was also initiated to quantify, understand, and predict the evolution of global carbon sources and sinks (http://carbon.nasa.gov/). Under NASA's sponsorship, several national or regional maps of forest biomass and height have been produced based on remote sensing observations. Lefsky (2010) developed a global forest canopy height map from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Geoscience Laser Altimeter System (GLAS). Simard, Pinto, Fisher, and Baccini (2011) globally mapped the forest canopy height with GLAS data at 1-km spatial resolution. The gaps between footprints of GLAS were predicted by the model of LiDAR height index as a function of forest type, tree cover, elevation, and climatology maps. Saatchi et al. (2011) presented a benchmark map of biomass carbon stocks over 2.5 billion ha of all tropical forests on three continents. The total carbon stocks in live biomass were mapped by extrapolating the estimates from 4079 in situ inventory plots and GLAS footprints over the land- scape using optical and microwave imagery. These existing global datasets of biomass or forest height are only approximations based on combining land cover type and representative carbon values, instead of measurements of actual biomass or height (Hall et al., 2011). The most accurate mapping of forest biomass should be built on the direct measurement of forest structures such as provided by the LiDAR data. Remote Sensing of Environment xxx (2014) xxx–xxx ⁎ Corresponding address at: A20 north, Datun road, Chaoyang district, Beijing 100101, China. E-mail address: niwj@radi.ac.cn (W. Ni). RSE-09266; No of Pages 9 http://dx.doi.org/10.1016/j.rse.2014.12.007 0034-4257/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse Please cite this article as: Ni, W., et al., Extraction of ground surface elevation from ZY-3 winter stereo imagery over deciduous forested areas, Re- mote Sensing of Environment (2014), http://dx.doi.org/10.1016/j.rse.2014.12.007