Stochastic gradient boosting classification trees for forest fuel types mapping through airborne laser scanning and IRS LISS-III imagery

This paper presents an application of Airborne Laser Scanning (ALS) data in conjunction with an IRS LISS-III image for mapping forest fuel types. For two study areas of 165 km² and 487 km² in Sicily (Italy), 16,761 plots of size 30-m × 30-m were distributed using a tessellation-based stratified sampling scheme. ALS metrics and spectral signatures from IRS extracted for each plot were used as predictors to classify forest fuel types observed and identified by photointerpretation and fieldwork. Following use of traditional parametric methods that produced unsatisfactory results, three non-parametric classification approaches were tested: (i) classification and regression tree (CART), (ii) the CART bagging method called Random Forests, and (iii) the CART bagging/boosting stochastic gradient boosting (SGB) approach. This contribution summarizes previous experiences using ALS data for estimating forest variables useful for fire management in general and for fuel type mapping, in particular. It summarizes characteristics of classification and regression trees, presents the pre-processing operation, the classification algorithms, and the achieved results. The results demonstrated superiority of the SGB method with overall accuracy of 84%. The most relevant ALS metric was canopy cover, defined as the percent of non-ground returns. Other relevant metrics included the spectral information from IRS and several other ALS metrics such as percentiles of the height distribution, the mean height of all returns, and the number of returns.     

Direct georeferencing of airborne LiDAR data in national coordinates

The topographic mapping products of airborne light detection and ranging (LiDAR) are usually required in the national coordinates (i.e., using the national datum and a conformal map projection). Since the spatial scale of the national datum is usually slightly different from the World Geodetic System 1984 (WGS 84) datum, and the map projection frame is not Cartesian, the georeferencing process in the national coordinates is inevitably affected by various geometric distortions. In this paper, all the major direct georeferencing distortion factors in the national coordinates, including one 3D scale distortion (the datum scale factor distortion), one height distortion (the earth curvature distortion), two length distortions (the horizontal-to-geodesic length distortion and the geodesic-to-projected length distortion), and three angle distortions (the skew-normal distortion, the normal-section-to-geodesic distortion, and the arc-to-chord distortion) are identified and demonstrated in detail; and high-precision map projection correction formulas are provided for the direct georeferencing of the airborne LiDAR data. Given the high computational complexity of the high-precision map projection correction approach, some more approximate correction formulas are also derived for the practical calculations. The simulated experiments show that the magnitude of the datum scale distortion can reach several centimeters to decimeters for the low (e.g., 500 m) and high (e.g., 8000 m) flying heights, and therefore it always needs to be corrected. Our proposed practical map projection correction approach has better accuracy than Legat’s approach,¹ but it needs 25% more computational cost. As the correction accuracy of Legat’s approach can meet the requirements of airborne LiDAR data with low and medium flight height (up to 3000 m above ground), our practical correction approach is more suitable to the high-altitude aerial imagery. The residuals of our proposed high-precision map projection correction approach are trivial even for the high flight height of 8000 m. It can be used for the theoretical applications such as the accurate evaluation of different GPS/INS attitude transformation methods to the national coordinates.     

利用LS_AR模型对极移参数的中长期预报

为了满足深空探测器自主导航定位对极移参数中长期预报的需求,阐述了基于LS_AR模型的极移参数中长期预报和精度评定的原理,提出了4种改进方案对LS_AR模型的构建进行优化,并利用IERS提供的1990～1996年的极移参数的时间序列检验4种优化方案,得到了最优的预报模型,在400 d跨度上,其预报结果的平均绝对误差比未优化的模型小3 mas左右。     

Development of a GIS data model with spatial,temporal and attribute components based on object-oriented approach

This paper presents a conceptual data model, the STA-model, for handling spatial, temporal and attribute aspects of objects in GIS. The model is developed on the basis of object-oriented modeling approach. This model includes two major parts: (a) modeling the signal objects by STA-object elements, and (b) modeling relationships between STA-objects. As an example, the STA-model is applied for modeling land cover change data with spatial, temporal and attribute components.     

Generation and study of satellite gravity over Gujarat,India and their possible correlation with earthquake occurrences

High-resolution satellite gravity data have been generated and utilized to infer subsurface geological structures in the area of devastating earthquake that struck the Bhuj region in Gujarat on 26 January 2001. Latitudinal gravity profiles have been generated in the Bhuj, Anjar and IBF regions across the epicentres (23.5° N, 69.8° E/M_w 7.0 in 2001; 23.2° N, 70° E/M_w 7.0 in 1956; 24.2° N, 69.2° E/M_w 7.8 in 1819). Substantial differences in gravity anomaly patterns as high as 37 mGal could be observed existing near the epicentre regions. These gravitational differences might have caused due to the plate tectonic processes and due to the changes in densities of different lithospheric zones/sedimentary layers. Temporal variations of the satellite-derived gravity and their probable relations with already occurred major earthquakes in this region have been studied. Hence we conclude that drastic changes in gravity anomalies can be considered as a precursor for occurrences of substantially large earthquakes.     

一等水准点之记标准化与规范化研究

为保证一等水准点之记精度与质量,提高测绘人员野外工作效率,对目前的一等水准点之记进行了探讨与分析,指出了其详细位置图与点位,详细说明表达、标石断面图绘制和经纬度书写及交通路线描述中存在的缺点,并基于此提出了若干改进意见,这在一定程度上促进了一等水准点之记信息的标准化与规范化。     

三维数字城市在道路规划设计中的应用研究

＂数字城市＂建设成果在国民经济建设中逐渐得到广泛应用,以直观、可视化、信息更加丰富为显著特点的＂三维数字城市＂建设成果,成为应用创新的助推剂,而当前,传统的依靠计算机辅助设计软件开展道路设计规划成为一种需要突破的变革趋势,选择基于三维数字城市建设成果开展道路规划设计,以其显著的优势成为道路设计规划变革的新途径。     

论军事测绘学与军事地理学发展的“分异”与“聚焦”

军事测绘学和军事地理学的演进与发展,都有近两千多年的历史,如今都已进入信息时代,成为分属工科和理科的两门独立的学科。本文论述了军事测绘学和军事地理学的研究对象、内容、范围和方法;分析了军事测绘学和军事地理学各自的发展过程,描述了各自的演进轨迹,特别是分析了信息时代的军事测绘学和军事地理学的发展趋势和各自特点;就军事测绘学和军事地理学在战场地理环境信息保障中的作用,分别从战场地理环境信息保障的两种思维、发展过程、发展特点和发展趋势等几个方面,分析了军事测绘学和军事地理学的"分异"与"聚焦";最后,从哲学的高度论述了"空间与时间一起构成运动着的物质存在的两种基本形式"和"空间参照与时间参照是自然与社会现象的两个基本参照系统"的观点,认为军事测绘学和军事地理学都是研究存在于空间和时间之中且运动着的物质,但研究的具体对象、内容、范围和方法有很大区别,必将在无限和有限统一的空间和时间中深化各自的研究内容、开拓各自的研究范围,创新各自的研究方法,同时又更加紧密地聚焦于战场地理环境信息保障。     

平顶山城区碳环境演变时间序列分析

大气中日益上升的温室气体浓度,已导致温室效应日益增强,从而引发一系列不利的环境与生态后果,并会对世界粮食生产、水资源利用等关系人类生存发展的方面产生重要影响。1994~2014年是平顶山城市化进程不断加快和经济社会高速发展的时期,土地利用、人口、能源消耗和城市植被等影响碳源、碳汇的主要方面也都发生了重大的变化。将1994~2014年河南省平顶山市城区的碳平衡变化情况作为研究对象,计算出碳平衡主要影响因素各自的变化情况并加以分析,得出有关平顶山城区碳环境演变的结论。最后,为促进平顶山城区的碳源碳汇平衡,提出实现城市快速发展过程中低碳效应策略。     

行业高校测绘卓越工程师多元化培养模式构建研究与实践

“测绘卓越工程师教育培养计划”是《国家中长期教育改革和发展规划纲要》高等教育改革和发展中具有战略性意义的一项重要任务。本文紧抓人才培养模式创新的关键性要素作为切入点,创建了一套行业需求为导向的测绘工程专业卓越人才培养体系,搭建“高工程素质、强实践能力”的人才培养模式,完善专业课程体系,加强师资队伍建设,强化多元实践教学,构筑创新实践平台,着力提高学生的工程意识、工程素质和工程实践能力。