三维坐标转换的公共点选择方法     

牛琳  陈建平  田毅 《北京测绘》2007,(4):9-11

三维坐标变换中转换参数直接影响到转换点的精度,而转换参数与公共点的分布和精度有关。本文通过以转换点的拟合误差最小为目标函数求解转换参数,逐步剔除精度不高和分布不合理的公共点,使得转换参数相对于所有的转换点达到局部最优。最后通过模拟实例证明:通过该方法获取的转换参数与求得的转换点精度优于常规方法。  相似文献   

东北三省湿地演化特征遥感分析     

邢宇  张汉女  姜琦刚  李文庆 《湿地科学与管理》2015,11(2):50-54

以1976年MSS、2001年ETM和2007年CBERS为遥感数据源,利用人机交互目视解译和野外检验方法获取湿地数据,定量分析东北三省湿地动态变化的相对速率、位移和类型转化,为东北湿地资源的保护与合理利用提供科学依据。结果表明:黑龙江、吉林、辽宁三省湿地面积分别为42 249.71 km2、10 737.95 km2、9 744.79 km2;32年来全区湿地先减少后快速增加,黑龙江省湿地面积变化的幅度最大,吉林省湿地变化的相对速率最大;东北三省湿地重心总体位于黑龙江哈尔滨市和宾县之间,32年来有向西移动的趋势;湿地与非湿地之间转化明显,其中大部分转向人工湿地,沼泽转化率高。  相似文献   

Transformation of South African industrial fisheries     

Jesper Raakjær Nielsen  Mafaniso Hara 《Marine Policy》2006

South African industrial fisheries have been dominated by a few large companies. The Marine Living Resources Act (MLRA) of 1998 emphasised that equity was to be achieved by redistribution through co-operative strategies among stakeholders. Instead, the reallocation of fishing rights has been treated as a resource management issue rather than a socio-economic challenge. Further, the institutional structures for transformation have been inappropriate. This paper investigates the institutional dynamics and discrepancies associated with transformation and concludes that the process became locked in a path dependency, which will eventually undermine the intentions of transformation.  相似文献   

Developing soil indices based on brightness,darkness, and greenness to improve land surface mapping accuracy     

Bingwen Qiu  Ke Zhang  Zhenghong Tang  Chongcheng Chen  Zhuangzhuang Wang 《地理信息系统科学与遥感》2017,54(5):759-777

Soil, as one of the three basic biophysical components, has been understudied using remote sensing techniques compared to vegetation and impervious surface areas (ISA). This study characterized land surfaces based on the brightness–darkness–greenness model. These three dimensions, brightness, darkness, and greenness, were represented by the first Tasseled Cap Transformation (TC1), Normalize Difference Snow Index (NDSI), and Normalized Difference Vegetation Index (NDVI), respectively. The Ratio Index for Bright Soil (RIBS) was developed based on TC1 and NDSI, and the Product Index for Dark Soil (PIDS) was established by TC1 and NDVI. Their applications to the Landsat 8 Operational Land Imager images and 500 m 8-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) in China revealed the efficiency. The two soil indices proficiently highlighted soil covers with consistently the smallest values, due to larger TC1 and smaller NDSI values in bright soil, and smaller NDVI and TC1 values in dark soil. The RIBS is capable of distinguishing bright soil from ISA without masking vegetation and water body. The spectral separability bright soil and ISA were perfect, with a Jeffries–Matusita distance of 1.916. And the PIDS was the only soil index that could discriminate dark soil from other land covers including ISA. The soil areas in China were classified using a simple threshold method based on MODIS images. An overall accuracy of 94.00% was obtained, with the kappa index of 0.8789. This study provided valuable insights into developing indices for characterizing land surfaces from different perspectives.  相似文献   

Employment in Cape Town’s lodging sector: opportunities, skills requirements, employee aspirations and transformation     

Kudzayi Chitiyo Maumbe  Laeticia J. Van Wyk 《GeoJournal》2008,73(2):117-132

Since the attainment of democracy in 1994 one of the major concerns of the South African government has been to address the social and economic injustices that characterised the apartheid regime. With tourism on the rise in South Africa and international arrivals growing at a rate almost triple the global rate, the tourism industry has been identified as one of the important industries to drive the transformation agenda. This study sought to assess the employment situation in Cape Town’s lodging sector, identify the existing types of jobs and skills requirements of the sector, determine career aspirations of and skills development needs for lodging sector employees as well as asses the state of transformation. Study findings showed that the lodging sector is labour intensive, requires low academic skill, and offers low paying employment following the findings that about a quarter of the respondents indicated that their jobs didn’t require any formal qualification, the average working day was 9.2 h and 52% earned below R3,500 a month. The study showed significant differences in income based on race. White employees earned significantly more than their black and coloured counterparts. However, white employees working as general labour were also significantly more qualified than their black and coloured counterparts. There was a significant positive relationship between income and length of service for white employees, but the same wasn’t true for black and coloured employees. There was a significant negative relationship between length of service and academic qualifications for black employees implying that black people’s length of service for one employer decreases as they become more academically qualified. Also significant was skills development opportunities based on gender. Significantly more females than males had attended on-the-job training programs.  相似文献   

Vector methods to compute azimuth, elevation, ellipsoidal normal, and the Cartesian ( X , Y , Z ) to geodetic ( φ , λ , h ) transformation     

J. Feltens 《Journal of Geodesy》2008,82(8):493-504

Vector-based algorithms for the computation of azimuth, elevation and the ellipsoidal normal unit vector from 3D Cartesian coordinates are presented. As a by-product, the formulae for the ellipsoidal normal vector can also be used to iteratively transform rectangular Cartesian coordinates (X, Y, Z) into geodetic coordinates (φ, λ, h) for a height range from −5600 km to 10⁸ km. Comparisons with existing methods indicate that the new transformation can compete with them.  相似文献   

Spatial correlation for transformation uncertainty and its applications     

Jianye Ching  Kok-Kwang Phoon  Tsai-Jung Wu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(4):294-311

This paper shows that the transformation uncertainty varies in space and can be decomposed into (a) a slowly fluctuating component contributed by the systematic bias for a local site and (b) a rapidly fluctuating component partly contributed by the measurement error. Based on a piezocone database, the slowly fluctuating component is found to have a vertical scale of fluctuation (SOF) of 17–60 m, larger than the vertical SOFs for most soil properties and characteristic dimensions for many geotechnical structures. This paper provides an empirical basis to justify the assumption that the transformation uncertainty is fully correlated in space.  相似文献   

再论全球变网格多层原始方程差分模式的设计     

廖洞贤 《应用气象学报》1999,10(2):141-150

在修正的MM4和一个有限域变网格差分模式的基础上,设计了全球变网格多层原始方程差分模式。可以证明:设计的模式具有质量、能量守恒等整体性质,并具有正确的动、位能转换关系。为了克服高纬地区经线辐合带来的时间步长须取得很小的问题,给出了不进行滤波处理并仍能保持整体性质的解决办法。  相似文献   

广西各地的雨季开始与汛期雨量分布型的分析   总被引：3，自引：0，他引：3  

吴恒强 《热带地理》2003,23(2):126-129,153

统计分析了广西各地雨季开始日的时空分布特点,指出江南极锋雨带南移使广西雨季自北向南相继开始,NE季风与SE季风共同作用使广西雨季东部先于西部,地处云贵高原余脉、右江上游的百色,雨季的开始与南海热带季风爆发有关.分析了广西各地主汛期雨量分布的"单峰型"和"双峰型"形成原因以及单双峰型的转换机理,指出影响广西的热带气旋频数大小的变化,是后汛期峰值时隐时现的主要原因.对全区性雨季偏早或偏迟年份的雨量和雨量分布型也作了对比分析,所揭示的相关事实,对天气预测有一定参考意义.  相似文献   

1nm锰矿相结构稳定性的研究   总被引：4，自引：1，他引：3  

钱江初 《海洋学报》1998,20(3):56-63

对在潮湿状态和经室温干燥后的人工合成Slnm锰矿相进行X衍射测定结果显示:1nm锰矿相与0.7nm锰矿相之间存在某种相变关系,那些结构不稳定的S1nm锰矿相,由于干燥等原因而失去层间-OH-H₂O层,而使原先的1nm相“崩塌”成为0.7nm锰矿相.1nm锰矿相结构稳定性主要是由被结合进层间的Cu、Co、Ni等二价金属阳离子的特性与数量所决定的,其所含的金属阳离子的数量与其锰矿相的结构稳定性呈正相关,而不同的金属阳离子在稳定1nm锰矿相的结构的能力的大小可排列为:Ni>Cu>Co>Zn>Ca≥Mg>Na.  相似文献