RASTER AND VECTOR DATA STRUCTURES

RASTER AND VECTOR DATA STRUCTURES

RASTER AND VECTOR DATA STRUCTURES

 

 Raster Data Structure

Raster data is based on a uniform grid of cells or pixels that represent an area of interest. Individual cells can be identified by the row and column they occupy. Each cell is by definition
A homogeneous unit with respect to its attributes. Raster data formats are used in satellite imagery and raster based GIS packages such as Grass, IDRISI, Sage, UNIX ARC/INFO, and the Spatial Analyst extension of ArcView 3.1.

Benefits of Raster Data Structure

1. Neighborhood locations can be analyzed.
2. Accommodates discrete data such as soils as well as continuous data such as topography.
3. Processing algorithms are easier than for vector data sets.
4. Compatible with other data collection and manipulation software such as in remote sensing.

Vector Data Structure

Vector data represents features as points, lines, and polygons. A point feature is an x and y coordinate, a line is a string of consecutive points, and a polygon is a string of consecutive points that closes back upon itself. Vector data sets can have topology (see section 3.5). Topology means that, in addition to the position of every feature, the software maintains the spatial relationships of adjacency and connectivity between features (i.e., it “knows” where all features are and how the relate to each other).

Benefits of Vector Data Structure

1. Less storage space is needed because many pixels don’t have to be stored for a homogeneous area.
2. Feature types can be individually retrieved such as roads or water features,
3. It is easier to associate a variety of descriptive resource data with a single resource feature.
4. Digitized data does not have to be converted.
5. Vector data set graphics tend to be of a higher quality.