What is a Shapefile?

A. Leverkuhn

A shapefile is a type of file format used to store information about primitive shapes. Shapefiles do not capture three-dimensional data, but they are often used to show topographical features in two dimensions. A shapefile is also called an ESRI shapefile after the company, Environmental Systems Research Institute, that created this kind of file in the 1990s.

Shapefiles are often used to depict lakes or waterways on maps while working with Geographic Information Systems.
Shapefiles are often used to depict lakes or waterways on maps while working with Geographic Information Systems.

Shapefiles are most often used for GIS, or geographical information systems. GIS uses shapefiles to depict shaped landmarks such as lakes or waterways. The data from shapefiles is stored with other information to help GIS programs map for their intended uses.

These days, companies and municipalities use GIS to map assets, to monitor public resources, or for a wide range of other goals. Engineers use GIS information and conducting studies about how new development will impact the community, or for other issues related to land use. ESRI was originally a company that used shapefiles for land use applications.

As a geospatial type of data file, a shapefile has several critical components. This type of file must include three different kinds of subfiles for data. The first one, .shp, represents the actual “feature geometry” or shapes. The .shx format file holds a kind of positional index for relating shapes to one another. A separate .dbf component holds information about the shapes that may be funneled into a database for advanced use.

Along with these mandatory features, a shapefile often includes other subfiles such as .prj that deals with projection, and various other files, many of which are “read-only” and include indexes for the shapes that are represented. Shapefiles deal with coordinates in terms of a X axis and a Y axis. A lot of the design of this file format helps to “handle” the shapes and their relationships to one another. Without this kind of advanced design, storing shapes is meaningless.

GIS systems that include the use of shapefiles have a lot of promise in helping planners to advance various land-use goals. Some of this kind of software leads to a greater ability for stewardship of local environmental resources, and better planned development in communities. Another great feature of these kinds of systems is that the owners of large mobile assets can track vehicles and equipment in real time. All of these uses make GIS and its software components a growing part of 21st century administration.

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