数据仓库和联机分析处理 (OL AP)是第三代数据库系统的两个重要新技术。由于没有对 OL AP形成准确的、共同认可的数据概念模型 ,造成目前一些支持 OL AP的数据模型都有一些不合理的限制 ,除非这些模型重新设计 ,否则不能回答特殊类型的...数据仓库和联机分析处理 (OL AP)是第三代数据库系统的两个重要新技术。由于没有对 OL AP形成准确的、共同认可的数据概念模型 ,造成目前一些支持 OL AP的数据模型都有一些不合理的限制 ,除非这些模型重新设计 ,否则不能回答特殊类型的询问。在此基础上 ,形式化地定义了一种基于关系的简单、直观的描述复杂大型数据的星型数据模型 ,并设计了 2个简单的星型关系代数以支持在该数据模型上的 OL AP操作。展开更多
Digital elevation model （DEM） is the most popular product for three-dimensional （3D） digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sa...Digital elevation model （DEM） is the most popular product for three-dimensional （3D） digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sampling distances （GSD）. Space-borne opti- cal and synthetic aperture radar （SAR） imaging are two of the most preferred and modern techniques for DEM generation. Using them, global DEMs that cover almost entire Earth are produced with low cost and time saving processing. In this study, we aimed to assess the Satellite pour robservation de la Terre-5 （SPOT-5）, High Resolution Stereoscopic （HRS）, the Advanced Space-borne Thermal Emission and Reflection Radiometer （ASTER）, and the Shuttle Radar Topography Mission （SRTM） C-band global DEMs, produced with space-borne optical and SAR imaging. For the assessment, a reference DEM derived from 1 ： 1000 scaled digital photogrammetric maps was used. The study is performed in 100 km2 study area in Istanbul including various land classes such as open land, forest, built-up land, scrub and rough terrain obtained from Landsat data. The analyses were realized considering three vertical accuracy types as fundamental, supplemental, and consolidated, defined by national digital elevation program （NDEP） of USA. The results showed that, vertical accuracy of SRTM C-band DEM is better than optical models in all three accuracy types despite having the largest grid spacing. The result of SPOT-5 HRS DEM is very close by SRTM and superior in comparison with ASTER models.展开更多
文摘数据仓库和联机分析处理 (OL AP)是第三代数据库系统的两个重要新技术。由于没有对 OL AP形成准确的、共同认可的数据概念模型 ,造成目前一些支持 OL AP的数据模型都有一些不合理的限制 ,除非这些模型重新设计 ,否则不能回答特殊类型的询问。在此基础上 ,形式化地定义了一种基于关系的简单、直观的描述复杂大型数据的星型数据模型 ,并设计了 2个简单的星型关系代数以支持在该数据模型上的 OL AP操作。
基金Under the auspices of Scientific Research Project Coordinatorship of Yildiz Technical University,Turkey(No.20100503KAP01)
文摘Digital elevation model （DEM） is the most popular product for three-dimensional （3D） digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sampling distances （GSD）. Space-borne opti- cal and synthetic aperture radar （SAR） imaging are two of the most preferred and modern techniques for DEM generation. Using them, global DEMs that cover almost entire Earth are produced with low cost and time saving processing. In this study, we aimed to assess the Satellite pour robservation de la Terre-5 （SPOT-5）, High Resolution Stereoscopic （HRS）, the Advanced Space-borne Thermal Emission and Reflection Radiometer （ASTER）, and the Shuttle Radar Topography Mission （SRTM） C-band global DEMs, produced with space-borne optical and SAR imaging. For the assessment, a reference DEM derived from 1 ： 1000 scaled digital photogrammetric maps was used. The study is performed in 100 km2 study area in Istanbul including various land classes such as open land, forest, built-up land, scrub and rough terrain obtained from Landsat data. The analyses were realized considering three vertical accuracy types as fundamental, supplemental, and consolidated, defined by national digital elevation program （NDEP） of USA. The results showed that, vertical accuracy of SRTM C-band DEM is better than optical models in all three accuracy types despite having the largest grid spacing. The result of SPOT-5 HRS DEM is very close by SRTM and superior in comparison with ASTER models.
