Vector Data

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Vector Data Structures

GRASS 6 Vector Architecture

The GRASS vector data model includes the description of topology, where besides the coordinates describing the location of the primitives (points, lines, boundaries and centroids), their spatial relations are also stored. In general, topological GIS require a data structure where the common boundary between two adjacent areas is stored as a single line, simplifying the map maintenance.

The following vector objects are defined:

  • point
  • line: directed sequence of connected vertices with 2 endpoints called nodes;
  • boundary: the border line to describe an area;
  • centroid: a point within a closed boundary;
  • area: the topological composition of centroid and boundary;
  • face: a 3D area;
  • kernel: a 3D centroid in a volume (not yet implemented);
  • volume: a 3D corpus, the topological composition of faces and kernel (not yet implemented).

Note: all lines and boundaries can be polylines (with nodes in between).

Specs

ESRI Shapefile

Simple Features

SVG