GIS Using Vector-Based Data Representation

Geographic information systems (GIS) technology combines geographic science with tools for comprehension and collaboration.

FREMONT, CA: Most GIS software products are primarily concerned with the use and editing of vector geodatabases, with additional components designed to operate with raster-based geodatabases.

Vector data

Vector data allow for the representation of real-world features in a GIS system. Anything visible on the terrain is referred to as a feature. Vector data is classified as point, line (or arc), or polygon.

Point Data

The most often used type of data is point data, representing non-adjacent features and discrete data points. Because points have no dimensions, this dataset cannot be used to calculate length or area. Examples include schools, places of interest, and, in the case below, the locations of bridges and culverts. Additionally, abstract points are represented using point characteristics. For example, point locations could correspond to city or place names.

Line Data

Linear characteristics are represented using line (or arc) data. Rivers, pathways, and streets are all common examples. Since line characteristics have only one dimension, they can only be used to measure length. Line features have a beginning and an end. Road centerlines and hydrology are frequent examples. The symbols used to differentiate arc features are line types (solid lines versus dashed lines) and color and line thickness combinations. In the example below, roads are shown by a solid black line, while a dashed blue line denotes hydrology.

Polygon Data

Polygons are used to show areas such as the perimeter of a city, a lake, or a forest on a large scale map. Due to the two-dimensional nature of polygon features, they can determine the size and perimeter of a geographic feature.

The most frequent way to distinguish polygon features is to employ a thematic mapping zymology (color schemes), patterns, or, in the case of numeric gradation, a color gradation scheme.

Both line and point feature data are substantially lower scale representations of polygon data. They contribute to clutter reduction by centralizing data storage.

When the features are magnified, the point position of a school is more accurately represented by a collection of building footprints indicating the campus's physical location.

A street centerline file's line features only represent the street's physical position. If a higher degree of spatial resolution is required, a street curbwidth file would be used to depict the road's width and any features such as medians and right-of-ways (or sidewalks).

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