Symbol portrayal is an important function of GIS. Sharing symbolic information in different GIS platforms is necessary for GIS applications and users. This paper discusses the necessity, possibility and solution techn...Symbol portrayal is an important function of GIS. Sharing symbolic information in different GIS platforms is necessary for GIS applications and users. This paper discusses the necessity, possibility and solution technique of sharing a symbol library in different GIS platforms. The route map is designed as follows： first, to set up a general data model for the symbol library, then to design a standard exchange format, and finally to call on the GIS manufacturer to provide the interchange tools for their symbol library for the standard exchange format. This paper analyzes the general characteristics of GIS symbolic library, gives a symbol library model and a draft of XML schema of the symbol library exchange format.展开更多
The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic （SSURGO） Database to provide a more holistic...The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic （SSURGO） Database to provide a more holistic view of the role of soil-forming factors in pedogenesis than from isolated case studies. Soils with a salic horizon occupied an area of 11 000 km2, i.e., 0.1% of land area in the contiguous USA. These soils occur narrowly in three great groups （Aquisalids, Haplosalids and Halaquepts）, 11 subgroups, and 97 soil series. Soils with a salic horizon commonly had a mesic （50% of soil series） or thermic （19%） soil-temperature class, an aquic （89%） soil-moisture class, a mixed mineral class （79%）, a calcareous （52%） reaction class, a superaztive （59%） cation exchange activity class, and a fine （24% of soil series）, fine-loamy （24% of soil series）, or fine-silty （19% of soil series） particle-size class. Soils with a salic horizon were concentrated in the Basin and Range Province of western USA. The key pedogenic processes leading to the development of salic horizons were salinization, gleization, and calcification, with some evidence for argilluviation and silicification.展开更多
基金Supported by the Spatial Information Engineering Key Laboratory Found of Chinese National Surveying and Mapping Bureau.(No.200722)
文摘Symbol portrayal is an important function of GIS. Sharing symbolic information in different GIS platforms is necessary for GIS applications and users. This paper discusses the necessity, possibility and solution technique of sharing a symbol library in different GIS platforms. The route map is designed as follows： first, to set up a general data model for the symbol library, then to design a standard exchange format, and finally to call on the GIS manufacturer to provide the interchange tools for their symbol library for the standard exchange format. This paper analyzes the general characteristics of GIS symbolic library, gives a symbol library model and a draft of XML schema of the symbol library exchange format.
文摘The taxonomic hierarchy and nationwide distribution of soils with a salic horizon were studied using the USA Natural Resources Conservation Service Soil Survey Geographic （SSURGO） Database to provide a more holistic view of the role of soil-forming factors in pedogenesis than from isolated case studies. Soils with a salic horizon occupied an area of 11 000 km2, i.e., 0.1% of land area in the contiguous USA. These soils occur narrowly in three great groups （Aquisalids, Haplosalids and Halaquepts）, 11 subgroups, and 97 soil series. Soils with a salic horizon commonly had a mesic （50% of soil series） or thermic （19%） soil-temperature class, an aquic （89%） soil-moisture class, a mixed mineral class （79%）, a calcareous （52%） reaction class, a superaztive （59%） cation exchange activity class, and a fine （24% of soil series）, fine-loamy （24% of soil series）, or fine-silty （19% of soil series） particle-size class. Soils with a salic horizon were concentrated in the Basin and Range Province of western USA. The key pedogenic processes leading to the development of salic horizons were salinization, gleization, and calcification, with some evidence for argilluviation and silicification.
