What are the shapefile files?
ArcGIS shapefiles are made up of mandatory and optional files. The mandatory file extensions needed for a shapefile are .shp, .shx and .dbf. The optional files are: .prj, .xml, .sbn and .sbx
What is the function of each of these ArcGIS file types? You also may have wondered how to open GIS files…
If you have several hours to spare, you could go through the 34-page ESRI Shapefile Technical Description document.
If time is a factor, than we suggest to read further. Let’s take a closer inspection at what makes up an ArcGIS shapefile.
List of shapefile files
.shp: ESRI file that represents the feature geometry. Each shapefile has it’s own .shp file that can represent points, lines and polygons in a map. Mandatory
.shx: ESRI and AutoCAD shape index position. This type of file is used to search forward and backwards. Mandatory.
.dbf: Standard database file used to store attribute data and object IDs. .dbf can be opened in Microsoft Access or Excel. Mandatory.
.prj: This file type contains the metadata associated with the shapefiles coordinate and projection system. If this file does not exist, the error “unknown coordinate system” will appear. To fix this error, the “define projection” tool generates .prj files. Optional.
.xml: This file type contains the metadata associated with the shapefile. Delete this file, and you essentially delete your metadata. This file type (.xml) can be opened and edited in any text editor. Optional.
.sbn: Spatial index file that optimizes spatial queries. This file type is saved together with a .sbx file. These two files make up a shape index to speed up spatial queries. Optional.
.sbx: Similar to .sbn files, this file type speeds up loading times. It works with .sbn files to optimize spatial queries. We tested .sbn and .sbx extensions and found that there were faster load times when these files existed. It was 6 seconds faster (27.3 sec versus 33.3 sec) comparing with/without .sbn and .sbx files. Optional.
.cpg: These are optional plain text files that describes the encoding applied to create the Shapefile. If your shapefile doesn’t have a cpg file, then it has the system default encoding. Optional.
Mandatory and optional files that make up a shapefile
In Windows Explorer:
When moving shapefile files from one folder to another, you should drag and drop all the mandatory and optional files.
When moving shapefiles, it will move all the mandatory and optional files for you.
There are over 150 different GIS file extensions that exist. These file types are exclusively used in GIS. This doesn’t even include AutoCAD and common image formats.
The most common GIS file type are shapefiles. Even the USGS Earth Explorer accepts shapefiles as input to define boundaries.
Shapefiles are composed of 3 mandatory files .shp, .shx and .dbf. The optional files that make up a shapefile are: .xml, .prj, .sbn, and .sbx.
Recognize these differences and become a master of the ArcGIS shapefile.