Estimating sagebrush cover in semi-arid environments using Landsat Thematic Mapper data     

Ramesh Sivanpillai  Steven D. Prager  Thomas O. Storey 《International Journal of Applied Earth Observation and Geoinformation》2009

Sagebrush ecosystems of the western US provide important habitat for several ungulate and vertebrate species. As a consequence of energy development, these ecosystems in Wyoming have been subjected to a variety of anthropogenic disturbances. Land managers require methodology that will allow them to consistently catalog sagebrush ecosystems and evaluate potential impact of proposed anthropogenic activities. This study addresses the utility of remotely sensed and ancillary geospatial data to estimate sagebrush cover using ordinal logistic regression. We demonstrate statistically significant prediction of ordinal sagebrush cover categories using spectral (χ² = 113; p < 0.0001) and transformed indices (χ² = 117; p < 0.0001). Both Landsat spectral bands (c-value = 0.88) and transformed indices (c-value = 0.89) can distinguish sites with closed, moderate and open cover sagebrush cover categories from no cover. The techniques described in this study can be used for estimating categories of sagebrush cover in arid ecosystems.  相似文献   

长牡蛎F3 代快速生长选育群体生长特性的研究   总被引：1，自引：0，他引：1  

孔宁  李琪  丛日浩  王庆志  孔令锋 《海洋科学》2015,39(3):7-11

采用模型拟合方法研究了长牡蛎(Crassostrea gigas)F3代快速生长选育群体不同时期各生长性状的发育规律。结果表明,长牡蛎幼虫期壳高(SH)、壳长(SL)对日龄(t)的回归遵循Logistic模型,生长方程分别为SH=455.612/(1+9.500e-0.142t),R2=0.999;SL=462.476/(1+8.026e-0.108t),R2=0.996。幼虫期壳高与壳长成直线相关,回归方程为SL=0.76SH+18.82,R2=0.994。长牡蛎养成期各生长性状呈现明显的季节变化,壳高(SH)、壳长(SL)、壳宽(SW)和总质量(TW)对月龄(X)的多项式回归方程分别为SH=-0.0297X4+1.0365X3-12.0220X2+57.6500X-68.9260,R2=0.985;SL=-0.0173X4+0.5893X3-6.5702X2+30.2420X-34.4150,R2=0.986;SW=-0.0068X4+0.2620X3-3.2806X2+16.9170X-22.1410,R2=0.956;TW=-0.0219X4+0.8234X3-10.1680X2+50.7040X-85.4110,R2=0.972。壳高、壳长、壳宽与总质量均呈幂函数相关,回归方程分别为SH=23.645TW0.3213,R2=0.998;SL=12.337TW0.3776,R2=0.995;SW=6.611TW0.3589,R2=0.981。  相似文献   

建筑物立面分类与DIM点云滤波     

崔颖  黄鹤  刘祥磊  罗德安 《测绘通报》2021,(3):55-59

针对目前基于近景摄影测量方法构建建筑物立面模型过程中因密集影像匹配（DIM）点云噪声所引起的建筑物立面TIN网格模型畸变问题,本文借鉴机器学习中样本学习的思想,对建筑物立面进行了分类并对DIM点云提出了相应的滤波方法,以达到去除DIM点云噪声和改善其TIN网格模型畸变的目的。其中,针对平面结构立面,采取先对点云样本进行学习计算构建数学立面模型所需参数,再对该立面模型设定阈值并对其点云进行滤波处理的方法;针对曲面结构立面,则结合DIM点云特性先将点云样本分类标记归为立面点与非立面点,再进行样本特征值学习,使用Logistic回归算法迭代计算求解最佳回归系数,从而构建滤波分类器的方法对立面点云进行滤波处理。试验结果表明,本文滤波处理方法能将立面DIM点云噪声有效识别并去除,而且使用该方法处理后所得点云构建的建筑物立面TIN网格模型精细化程度得到有效提高,模型质量得到明显改善。  相似文献   

复合混沌系统的矢量数据加密研究     

张翰林  王青山  邹永初 《测绘科学》2012,37(5):87-89

根据矢量数据的特点和混沌映射系统的加密方法,本文提出了一种基于Logistic映射和Chebyshev映射的复合混沌系统。它通过使用迭代状态的周期替换,并输出整数化的混沌映射序列,有效地避免计算机有限精度产生的累计误差。该算法有较强的随机性、抗穷举攻击能力、抵御已知明文攻击能力和较好的时间代价。经过安全性分析,本算法可以较好地用于矢量数据的加密。  相似文献   

北京市住宅用地开发压力与城市扩张预景——基于阻力面的分析   总被引：2，自引：1，他引：1  

俞孔坚  游鸿  许立言  袁弘 《地理研究》2012,31(7):1173-1184

基于城市经济学的一般理论,从市场机制下的供给方视角出发,提出了预测大都市区住房建设区位选择的一个新模型,并利用2005～2009年北京市新增住宅项目的抽样空间数据进行了实证研究,进而应用阻力面模型模拟了北京市未来住宅建设用地开发压力和城市扩张的空间格局。研究表明:北京市的新增住房用地区位选择总体上符合单中心同心圆的基本模型,但正在逐渐向等级制特征下的多中心格局演化,北部、西北部区县的中心城区以及南部新城、新开发区周边更有可能成为潜在的下一轮住宅建设核心区,从而成为城市扩张的重点区域。  相似文献   

历史遗址类旅游地的生命周期研究——以美国14家历史遗址公园为例     

杨小露  张红  张春晖 《地理科学进展》2019,38(6):918-929

实证研究中旅游地生命周期理论的运用潜力备受质疑。论文选取美国14家国家历史遗址公园为例,采用旅游研究中较少使用的四参数Logistic模型结合一次函数、二次函数、三次函数、高斯多峰分析法拟合旅游地的生命周期。研究发现：四参数Logistic模型结合一次函数、二次函数、三次函数能较好地拟合旅游地的生命周期;利用四参数Logistic曲线的上弯点、拐点、下弯点能定量的划分出旅游地的起步探索、发展、巩固、停滞阶段,一次函数、二次函数、三次函数能拟合旅游地的衰退或复兴阶段,这回答了学者们对生命周期阶段难以定量划分的质疑。根据旅游地停滞期之后的发展趋势还能归纳出该类旅游地的生命周期类型;高斯多峰分析法将旅游地的生命周期拟合成一个个波动的高斯峰,更大程度上保留了旅游地演进的波动特征;将高斯多峰分析法与四参数Logistic模型结合起来,不仅能定量划分旅游地的生命周期阶段,还能准确地描述在生命周期阶段内的波动情况,甚至分析各生命周期阶段对整个生命周期的影响和作用。  相似文献   

Estimating the starting time and identifying the type of urbanization based on dense time series of landsat-derived Vegetation-Impervious-Soil (V-I-S) maps – A case study of North Taiwan from 1990 to 2015     

《International Journal of Applied Earth Observation and Geoinformation》2020

Land cover and land use change (LCLUC) is a global phenomenon, and LCLUC in urbanizing regions has substantial impacts on humans and their environments. In this paper, a semi-automatic approach to identifying the type and starting time of urbanization was developed and tested based on dense time series of Vegetation-Impervious-Soil (V-I-S) maps derived from Landsat surface reflectance imagery. The accuracy of modeled V-I-S fractions and the estimated time of initial change in impervious cover were assessed. North Taiwan, one of the regions of the island of Taiwan that experienced the greatest urban LCLUC, was chosen as a test area, and the study period is 1990 to 2015, a period of substantial urbanization. In total, 295 dates of Landsat imagery were used to create 295 V-I-S fraction maps that were used to construct fractional cover time series for each pixel. Root Mean Square Error (RMSE)s for the modeled Vegetation, Impervious, and Soil were 25 %, 22 %, 24 % respectively. The time of Urban Expansion is estimated by logistic regression applied to Impervious cover time series, while the time of change for Urban Renewal is determined by the period of brief Soil exposure. The identified location and estimated time for newly urbanized lands were generally accurate, with 80% of Urban Expansion estimated within ±2.4 years. However, the accuracy of identified Urban Renewal was relatively low. Our approach to identifying Urban Expansion with dense time series of Landsat imagery is shown to be reliable, while Urban Renewal identification is not.  相似文献   

Integration of remote sensing,county-level census,and machine learning for century-long regional cropland distribution data reconstruction     

《International Journal of Applied Earth Observation and Geoinformation》2020

The Lower Mississippi Alluvial Valley (LMAV) was home to about ten million hectare bottomland hardwood (BLH) forests in the Southern U.S. It experienced over 80 % area loss of the BLH forests in the past centuries and large-scale afforestation in recent decades. Due to the lack of a high-resolution cropland dataset, impacts of land use change (LUC) on the LMAV ecosystem services have not been fully understood. In this study, we developed a novel framework by integrating the machine learning algorithm, county-level agricultural census, and satellite-based cropland products to reconstruct the LMAV cropland distribution during 1850–2018 at a 30-m resolution. Results showed that the LMAV cropland area increased from 0.78 × 10⁴ km² in 1850 to 6.64 × 10⁴ km² in 1980 and then decreased to 6.16 × 10⁴ km² in 2018. Cropland expansion rate was the largest in the 1960s (749 km² yr⁻¹) but decreased rapidly thereafter, whereas cropland abandonment rate increased substantially in recent decades with the largest rate of 514 km² yr⁻¹ in the 2010s. Our dataset has three notable features: (1) the depiction of fine spatial details, (2) the integration of the county-level census, and (3) the inclusion of a machine-learning algorithm trained by satellite-based land cover product. Most importantly, our dataset well captured the continuous increasing trend in cropland area from 1930–1960, which was misrepresented by other cropland datasets reconstructed from the state-level census. Our dataset would be important to accurately evaluate the impacts of historical deforestation and recent afforestation efforts on regional ecosystem services, attribute the observed hydrological changes to anthropogenic and natural driving factors, and investigate how the socioeconomic factors control regional LUC pattern. Our framework and dataset are crucial to developing managerial and policy strategies for conserving natural resources and enhancing ecosystem services in the LMAV.  相似文献   

赣南生态屏障区林地时空变化分情景模拟   总被引：1，自引：0，他引：1  

杨丽  傅春 《地理科学》2018,38(3):457-463

基于2000年和2010年土地利用遥感数据,从自然、区位、交通、人口和经济4个角度选取驱动因子,利用Logistic-CA-Markov土地利用综合模型预测赣南森林有林地、灌木林、疏林地和其它林地4种林地类型在当前模式、规划模式和保护模式3种情景下的空间演变格局。结果表明：① 到2020年,在当前模式和规划模式,林地总面积将减少,在保护模式则出现增加,3种情景都体现出有林地和其它林地增加、疏林地和灌木林缩减的趋势,只是增减幅度不同,但不论何种情形林地的组成结构都将发生较大程度的变化;② 3种情景都是以疏林地→有林地、有林地→其它林地和灌木林→有林地这3种类型的转化为主,向有林地的转化分布都比较分散,而向其它林地的转化却集中在安远、信丰、于都、赣县四县交界处;③ 相较于当前模式,在规划模式下集中在安远县及其周边的有林地向其它林地的转化出现大量缩减,在保护模式下这种缩减更加明显。  相似文献   

基于支持向量机的雷暴潜势预报初探   总被引：1，自引：0，他引：1       下载免费PDF全文

周明薇  肖稳安  张其林  周四清  彭双姿 《大气科学学报》2018,41(4):569-576

根据2008—2010年夏季邵阳地区的NCEP全球再分析资料(分辨率为1°×1°)和闪电定位资料,利用支持向量机(SVM)分类方法建立该地区雷暴潜势预报模型,并用测试样本检验了该模型的预报能力,同时与Logistic回归模型和Bayes判别法的预报效果进行了比较。结果表明,SVM模型的预报准确率为86.21%,虚警率为15.25%,漏报率为13.79%。对比三种模型的TSS技术评分,发现使用SVM方法建立的模型对邵阳地区雷暴预报的效果最好,评分值为0.79。因此,SVM方法所建立的模型可以为邵阳地区6 h的雷暴潜势预报提供一定的参考价值。  相似文献