【文章內(nèi)容簡(jiǎn)介】 ing arcs. Nodes can, however, be used to represent point features which connect segments of a linear feature (., intersections connecting street segments, valves connecting pipe segments). NODE 點(diǎn) 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 NODE 點(diǎn)的類型 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 NODE 點(diǎn)的存儲(chǔ) When nodes are used to represent point features, descriptive data is stored in a node attribute table (NAT). There is one record in the NAT for each node. The record is related to the node by the node抯 internal sequence number. At a minimum, the following items are contained in a NAT: ARC Internal sequence number of one of the arcs that connects at the node location. cover Internal sequence number of the node. coverID Userassigned feature ID. When an NAT is initially created, node IDs are automatically set equal to the node’s internal sequence number. 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 A node is an endpoint of an arc. The fromnode is the first vertex in the arc。 the tonode is the last vertex. Together, they define the direction of the arc. A node is shared by the set of arcs which connect to each other at the node. VERTEX 點(diǎn) 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 FNODE Internal sequence number of the fromnode. TNODE Internal sequence number of the tonode. LPOLY Internal sequence number of the left polygon。 set to 0 if the coverage does not contain polygons. RPOLY Internal sequence number of the right polygon。 set to 0 if the coverage does not contain polygons. LENGTH Length in coverage units. cover Internal sequence number (., the record number) of the arc in the ARC file. coverID： Userassigned feature ID. ARC 線 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 POLYGON 多邊形（面） 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 ? 圖幅范圍 EXTAND ( BND ) ? 投影類型 PRJ 文件 3） Coverage 中的空間描述特征 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 BOUNDARY(Xmin, Ymin, Xmax, Ymax) 圖幅范圍 EXTAND ( BND ) 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 Coverage extent represents the outer boundary of a coverage. It is the minimum bounding rectangle that defines the coordinate limits (extreme minimum and maximum coordinates) of coverage arcs and label points, and by definition, polygons, routesystems and regions. 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 All extent information for a coverage is stored in the BND file which contains the following items: XMIN The xcoordinate of the coverage extent lower left corner. YMIN The ycoordinate of the coverage extent lower left corner. XMAX The xcoordinate of the coverage extent upper right corner. YMAX The ycoordinate of the coverage extent upper right corner. The coordinates for links, tics and annotation can fall outside the BND. A coverage containing no arcs or label points (or a single label point) will have an undefined BND. 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 Projection ALBERS Zunits NO Units METERS Spheroid CLARKE1866 Xshift Yshift Parameters 25 0 /* 1st standard parallel 47 0 /* 2nd standard parallel 110 0 /* central meridian 0 0 /* latitude of projection39。s origin /* false easting (meters) /* false northing (meters) 投影文件 PRJ 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 4) Coverage 的屬性特征 Feature class Feature attribute table INFO database Feature attribute table coverage directory Point cover.PAT Arc cover.AAT Node cover.NAT Route cover.RATroute route.rat Section cover.SECsection route.sec Polygon cover.PAT Region cover.PATregion region.pat 北京師范大學(xué)資源科學(xué)研究所 /科學(xué)技術(shù)處 2022年度研究生課程：地理信息系統(tǒng)理論方法與應(yīng)用 5) Coverage 的存儲(chǔ)方法 Coverage 是一個(gè)目錄，其