Shapefiles

Shapefiles were developed by ESRI to hold and transfer GIS data. Shape files can be imported by all of ESRI's programs such as ArcView and ArcGIS. They can also be imported by a variety of other programs that support the Shapefile format. Shapefiles can hold several different types of information including, points, lines, polygons and database information.

Shapefile Data Sets. Shapefiles actually consist of a set of three files, each one holding a different part of the data. For example, a Shapefile set for Fulford Cave might look like this:

Fulford.shp – Fulford.inx – Fulford.dbf

Here is a description of each file type:

1. The Main File - SHP. The Main File holds the actual geographic data. It has the extension “SHP” and it can contain points, lines, flat surfaces or three-dimensional objects.

2. The Index File - INX. The Index File has the extension “INX” and holds a table of contents for the data in the Main File. Each entry in the Index File holds a pointer to one item in the main file. This make it easy to find, process and display individual items in the Main File.

3. Dbase Table - DBF. The DBase file is a standard “Dbase” database table file and has the extension “DBF”. Each row in the database is associated with one object in the Main File and one Entry in the Index File. Each field in the database contains an attribute for the items in the Main File. For example, if the Main File holds cave survey stations, one of the fields could hold the name of the station. Various ESRI software packages allow you to display attribute data from the database with the objects from the Main File. Thus, in the cave surveying example, station labels could be displayed next to the stations