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Question
What are Shapefiles? What are they used for? Which version number of the Shapefiles does JViews read?
Answer
A shape data set consists of three files:
- SHP file that contains geometrical information (for example, shape type and coordinates).
- DBF file that contains additional attribute information (for example, name or temperature).
- SHX file that contains an index for direct access to the SHP file.
Shapefiles do not contain any information about the rendering of the graphic objects (color, width, and so on).
For more information, you can download arcexplorer (for free) at the ESRI site. Colors are randomly generated when you load a SHP file. The user can then modify the symbology with an easy-to-use GUI.
And what exactly is this used for? (Which kind of applications would use it? ESRI applications?)
The size of a record is fixed in both the SHX and DBF files, but it is not fixed in the SHP file. The SHX file can be useful (for optimization purposes), as it provides the offset in the SHP file to a specific object record.
For example, if the SHP file is large, and you need to access the 1030th object (because you've performed some filtering operations using the DBF file) you will know that its definition starts at byte 10439 and can have direct access to the graphical object.
Support for SHX files will not be provided in the next release of JViews.
The shape reader of JViews 2.1 reads only the SHP file.
And which version number of the Shapefiles does JViews read?
ESRI doesn't give a version number to the Shapefile format. The specification document below was used for this.
ESRI Shapefile Technical Description, An ESRI White Paper, July 1998
