Shapefile
Definition
A shapefile is a popular geospatial vector data format supported by various geographic information system (GIS) software. It is typically used for storing the location, shape, and attributes (non-spatial information such as demographics, statistics, or classifications) of geographic features. This term is patented by Environmental Systems Research Institute (ESRI) and is essentially used for spatial vector data in the form of points, lines, and polygons, which can represent various geographical features — such as buildings, rivers, and states, respectively.
Shapefiles store data in three mandatory file types (.shp, .shx, .dbf) and can also include additional, optional files, such as an index to provide faster access to data (.sbn, .sbx), or the projection file (.prj) to store coordinate system data. These separate but related files must be kept together for the shapefiles to work correctly.
What is Shapefile?
A shapefile, in the context of geographic information systems, is a simple, non-topological file format designed to store the geometric location and attribute information of geographic features. These geographic features are usually seen in a map, but their data and attributes can be more than what's visible to the naked eye.
While primarily associated with ESRI, shapefiles are open specifications and can be read or written by many GIS software platforms. This makes shapefiles one of the most widely accepted and used file formats in GIS. Despite their widely accepted usage, shapefiles have limitations. For instance, they can't store null values, have a limit on attribute field lengths, can't hold topologic information, and have a file size limit.
Regardless of these limitations, shapefiles continue to be a convenient and ubiquitous option for the storage, exchange, and use of spatial data within the GIS community.
FAQs
What information does a shapefile contain?
A shapefile's primary file carries the main geometric data (i.e., points, lines, polygons), an index file to allow quick access to geometric data, and a dBASE file that contains attribute data. It can also contain several optional files that provide additional information like coordinate system data or indexes for faster data retrieval.
What are the limitations of a shapefile?
Some limitations of a shapefile include inability to store null values, a limit on attribute field lengths, inability to hold topologic information, inability to support curves such as circular arcs or Bezier curves, and a file size limit (2 GB for most systems).
Can other applications outside of ESRI use shapefiles?
Yes. Despite being developed by ESRI, shapefiles have become an industry-standard geospatial data format and are compatible with many GIS applications, including Atlas.
