地理信息系统GIS课件08.pptVIP

* Figure 8.11 A large dangle length can remove the overshoots, which should be removed, and the undershoot, which should not be removed. * Figure 8.12 A large fuzzy tolerance can remove duplicate lines (top), which should be removed, as well as features such as a small stream channel (middle), which should not be removed. * Figure 8.13 The allowable extend distance can remove the dangle by extending it to the line on the right. * Figure 8.14 To remove the overshoot a, first select it and then delete it. * Figure 8.15 To remove the pseudo node, select a and b, assign the same ID value to both, and un-split them. * 8.4.2 Editing Using Map Topology Map topology - temporary set of topological relationships When features from two different layers should coincide, such as a stream and a county boundary Cluster tolerance - can snap vertices and lines if they fall within the specified tolerance * 8.4.3 Editing Using Topology Rules Geodatabase model has 25 topology rules for point, line, and area features Editing is a three-step process Create new topology Validate topology Fixing errors * 8.5 Nontopological Editing Variety of basic editing operations that can modify simple features from existing features * 8.5.1 Edit Existing Features Extend/trim lines Delete/move features Reshape features Split lines and polygons * Figure 8.16 After a polygon of a shapefile is moved, a void area appears in its location. * Figure 8.17 Reshape a line by moving a vertex (a), deleting a vertex (b), and adding a vertex (c). * Figure 8.18 Sketch a line across the polygon boundary to split the polygon into two. * 8.5.2 Create Features from Existing Features Merge features Buffer features Union features Intersect features * Figure 8.19 Merge four selected polygons into one. * 8.6 Other Editing Operations Operations that cannot be classified as topological or nontopological * 8.6.1 Edgematching Figure 8.20 Edgematching matches the lines of two adjacent layers (top) so that the lines are continuous