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Since the original implementation, the basic strategy of the polygon overlay algorithm has remained the same, although the vector data structures that are used have evolved. [11] Given the two input polygon layers, extract the boundary lines. Cracking part A: In each layer, identify edges shared between polygons. Break each line at the junction ...
While the raster model is closely tied to the field conceptual model, objects can also be represented in raster, essentially by transforming an object X into a discrete field of presence/absence of X. Alternatively, a layer of objects (usually polygons) could be transformed into a discrete field of object identifiers.
The Geospatial Data Abstraction Library (GDAL) is a computer software library for reading and writing raster and vector geospatial data formats (e.g. shapefile), and is released under the permissive X/MIT style free software license by the Open Source Geospatial Foundation.
Moving the sea&ocean polygon to the "lakes" layer. 19. Set the LANDS-Polygons layer to Editable and Selectable. Cut (Ctrl+X) the sea&ocean polygon and paste it (Ctrl+V) to the lakes layer Coloring the political units. 20. Uncheck Selectable and Editable for all the vector layers, except the LANDS-Polygons layer.
Sliver polygons are typically created when polygons are automatically generated from lines that should be coincident (e.g., an international boundary following a river de jure, or two adjacent counties) but are not, due to the natural discrepancies that arise from manual or automated digitization. This can occur when a single layer is digitized ...
The polygonal map quadtree (or PM Quadtree) is a variation of quadtree which is used to store collections of polygons that may be degenerate (meaning that they have isolated vertices or edges). [ 9 ] [ 10 ] A big difference between PM quadtrees and edge quadtrees is that the cell under consideration is not subdivided if the segments meet at a ...
Traditionally, there are two broad methods used to store data in a GIS for both kinds of abstractions mapping references: raster images and vector. Points, lines, and polygons represent vector data of mapped location attribute references.
The Geography Markup Language (GML) is the XML grammar defined by the Open Geospatial Consortium (OGC) to express geographical features. GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions on the Internet.