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GIS shapefiles store geographic data in vector coordinates and can store point, line, and area data. They also store attribute information and can be manipulated or converted to other data types. They are smaller and quicker to create than other file types but are limited in the types of modifications that can be made.
A GIS shapefile is a file format used to store geographic information data in computer programs and GIS databases, such as ArcGIS and ArcCatalog. The file extension for shapefiles is .shp. It is a vector data format, which means that geometric data is stored in vector coordinates. GIS shapefiles don’t store topographic information, but they are useful for storing geographic data, such as the locations of buildings and roads.
Point, line and area data can be stored in a GIS shapefile. Each piece of information is stored as a separate entity in the file and these are called characteristics. A point item appears as a small dot on the map and is used to store information such as the location of buildings or trees. Linear features appear as solid lines and represent physical features, such as roads and rivers. Area elements are solid flat polygons, which can be used to represent information, such as census blocks or urban areas.
In addition to vector data displayed on a map, a GIS shapefile can also store attribute information. This is stored in a database table and all the records in the table are associated with the features on the map. An attribute table lists the vector coordinates for each feature, but can also be used to store other information about them, such as street names or census block population.
Shapefiles can be manipulated or converted to other data types in a variety of ways. Because the information is stored in vector coordinates, it’s relatively easy to add features to a GIS shapefile. The size or attributes of existing features in a shapefile can also be changed. Data from two or more shapefiles can be combined, or information in one attribute table can be linked to the table in another GIS file. Shapefiles can also be converted to a GIS raster file type, if more complex editing or statistical analysis is needed.
Compared to other file types often used to store geographic data, GIS shapefiles are generally smaller files that can be created and edited more quickly. The simpler data form of a GIS shapefile, however, also limits the types of modifications that can be made to the file and makes it unsuitable for storing topographic data. Shapefiles are often used in conjunction with other file types on the same map to perform complex geographic analysis.
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