GIS Data Types
Vectors
Vectors can be classified into three primary feature types: points, lines and polygons. Vector data is entered into a GIS by digitizing these features from a base map. All vector data is stored as an x,y coordinate, or a series of x,y coordinates.
The image below contains all the cities in Pennsylvania. These cities are represented as points.
![](/images/tutorials/gis-basics/pacities.jpg)
Locations on the earth surface are defined in terms of latitude and longitude. Data stored in a GIS are typically "projected" from a 3-dimensional sphere to a 2-dimensional (x, y) coordinate system. The graphic below shows a grid that represents a particular x, y coordinate system, such as Universal Transverse Mercator (UTM). If we were zoom in to Philadelphia, you would be able to see that this feature has an single location along the x and y axis. Other examples of point features could be wells, fire hydrants, or airport locations.
![](/images/tutorials/gis-basics/philaxy.jpg)
The image below shows a major river that flow through Pennsylvania. The Susquehanna River is represented by a line and is made up of a series of x,y coordinates.
![](/images/tutorials/gis-basics/parivers.jpg)
The line feature like the Susquehanna River, has a starting and ending point as indicated in red, and has a series of points between that form a line. In addition to location information a line feature has a length. Other examples of line features could be roads, pipelines, or railroads.
![](/images/tutorials/gis-basics/paseries.jpg)
The image below contains all the counties in Pennsylvania and each county would be a polygon feature.
![](/images/tutorials/gis-basics/pacounty2.jpg)
The polygon feature is also a series of x,y coordinates but it has the same beginning and ending point which closes the feature. This multi-sided figure represents an area on a map. In addition to location , polygons have attribute information such as its area or perimeter length. Example of polygons could be political boundaries, lakes or land parcels.
![](/images/tutorials/gis-basics/paerie.jpg)