Rasterization is a conversion process accompanied with information loss, which includes the loss of features＇ shape, structure, position, attribute and so on. Two chief factors that affect estimating attribute accura...Rasterization is a conversion process accompanied with information loss, which includes the loss of features＇ shape, structure, position, attribute and so on. Two chief factors that affect estimating attribute accuracy loss in rasterization are grid cell size and evaluating method. That is, attribute accuracy loss in rasterization has a close relationship with grid cell size; besides, it is also influenced by evaluating methods. Therefore, it is significant to analyze these two influencing factors comprehensively. Taking land cover data of Sichuan at the scale of 1：250,000 in 2005 as a case, in view of data volume and its processing time of the study region, this study selects 16 spatial scales from 600 m to 30 km, uses rasterizing method based on the Rule of Maximum Area （RMA） in ArcGIS and two evaluating methods of attribute accuracy loss, which are Normal Analysis Method （NAM） and a new Method Based on Grid Cell （MBGC）, respectively, and analyzes the scale effect of attribute （it is area here） accuracy loss at 16 different scales by these two evaluating methods comparatively. The results show that： （1） At the same scale, average area accuracy loss of the entire study region evaluated by MBGC is significantly larger than the one estimated using NAM. Moreover, this discrepancy between the two is obvious in the range of 1 km to 10 km. When the grid cell is larger than 10 km, average area accuracy losses calculated by the two evaluating methods are stable, even tended to parallel. （2） MBGC can not only estimate RMA rasterization attribute accuracy loss accurately, but can express the spatial distribution of the loss objectively. （3） The suitable scale domain for RMA rasterization of land cover data of Sichuan at the scale of 1：250,000 in 2005 is better equal to or less than 800 m, in which the data volume is favorable and the processina time is not too Iona. as well as the area accuracv loss is less than 2.5%.展开更多
川渝断面的洪板双回和黄万双回潮流分布不均,极大地限制了四川电网交流外送能力。对利用加装移相变压器(简称移相器)改善洪板双回和黄万双回的潮流分布,从而提高川渝断面输送极限的可行性进行了初步分析。首先,调研了移相器在国内外的...川渝断面的洪板双回和黄万双回潮流分布不均,极大地限制了四川电网交流外送能力。对利用加装移相变压器(简称移相器)改善洪板双回和黄万双回的潮流分布,从而提高川渝断面输送极限的可行性进行了初步分析。首先,调研了移相器在国内外的应用与研究情况。其次,简要介绍移相器的分类和基本原理、选址原则以及容量设计方法。最后,利用PSASP软件,对移相器在川渝断面应用的可行性进行了分析。研究表明,移相器能够显著提高川渝断面的输送极限,同时对改善500 k V站点的短路电流也有一定的作用。展开更多
基金The Independent Research of the State Key Laboratory of Resource and Environmental Information System,No.O88RA100SAThe Third Innovative and Cutting-edge Projects of Institute of Geographic Sciences andNatural Resources Research, CAS, No.O66U0309SZ
文摘Rasterization is a conversion process accompanied with information loss, which includes the loss of features＇ shape, structure, position, attribute and so on. Two chief factors that affect estimating attribute accuracy loss in rasterization are grid cell size and evaluating method. That is, attribute accuracy loss in rasterization has a close relationship with grid cell size; besides, it is also influenced by evaluating methods. Therefore, it is significant to analyze these two influencing factors comprehensively. Taking land cover data of Sichuan at the scale of 1：250,000 in 2005 as a case, in view of data volume and its processing time of the study region, this study selects 16 spatial scales from 600 m to 30 km, uses rasterizing method based on the Rule of Maximum Area （RMA） in ArcGIS and two evaluating methods of attribute accuracy loss, which are Normal Analysis Method （NAM） and a new Method Based on Grid Cell （MBGC）, respectively, and analyzes the scale effect of attribute （it is area here） accuracy loss at 16 different scales by these two evaluating methods comparatively. The results show that： （1） At the same scale, average area accuracy loss of the entire study region evaluated by MBGC is significantly larger than the one estimated using NAM. Moreover, this discrepancy between the two is obvious in the range of 1 km to 10 km. When the grid cell is larger than 10 km, average area accuracy losses calculated by the two evaluating methods are stable, even tended to parallel. （2） MBGC can not only estimate RMA rasterization attribute accuracy loss accurately, but can express the spatial distribution of the loss objectively. （3） The suitable scale domain for RMA rasterization of land cover data of Sichuan at the scale of 1：250,000 in 2005 is better equal to or less than 800 m, in which the data volume is favorable and the processina time is not too Iona. as well as the area accuracv loss is less than 2.5%.
文摘川渝断面的洪板双回和黄万双回潮流分布不均,极大地限制了四川电网交流外送能力。对利用加装移相变压器(简称移相器)改善洪板双回和黄万双回的潮流分布,从而提高川渝断面输送极限的可行性进行了初步分析。首先,调研了移相器在国内外的应用与研究情况。其次,简要介绍移相器的分类和基本原理、选址原则以及容量设计方法。最后,利用PSASP软件,对移相器在川渝断面应用的可行性进行了分析。研究表明,移相器能够显著提高川渝断面的输送极限,同时对改善500 k V站点的短路电流也有一定的作用。
