|
|
|
Fundamentals of GIS
Mapping Concepts, Features & Properties
A map represents geographic features or other spatial phenomena by graphically conveying information about locations and attributes. Locational information describes the position of particular geographic features on the Earth's surface, as well as the spatial relationship between features, such as the shortest path from a fire station to a library, the proximity of competing businesses, and so on. Attribute information describes characteristics of the geographic features represented, such as the feature type, its name or number and quantitative information such as its area or length.
Thus the basic objective of mapping is to provide
- descriptions of geographic phenomenon
- spatial and non spatial information
- map features like Point, Line, & Polygon.
Map Features
Locational information is usually represented by points for features such as wells and telephone pole locations, lines for features such as streams, pipelines and contour lines and areas for features such as lakes, counties and census tracts.
Point feature
A point feature represents as single location. It defines a map object too small to show as a line or area feature. A special symbol of label usually depicts a point location.
Line feature
A line feature is a set of connected, ordered coordinates representing the linear shape of a map object that may be too narrow to display as an area such as a road or feature with no width such as a contour line.
Area feature
An area feature is a closed figure whose boundary encloses a homogeneous area, such as a state country soil type or lake.
Map Characteristics
In addition to feature locations and their attributes, the other technical characteristics that define maps and their use includes:
- Map Scale
- Map Accuracy
- Map Extent and
- Data Base Extent
|
|
|