shptree

Purpose

Creates a quadtree-based spatial index for a shapefile. The default tree depth is calculated so that each tree node (quadtree cell) contains 8 shapes. Do not use the default with point files, a value between 6 and 10 seems to work ok. Your millage may vary and you’ll need to do some experimenting.

The shptree wiki page may also contain information on this utility.

Description

This utility is a must for any MapServer application that uses shapefiles. Shptree creates a spatial index of your shapefile, using a quadtree method. This means that MapServer will use this index to quickly find the appropriate shapes to draw. It creates a file of the same name as your shapefile, with a .qix file extension. The quadtree method breaks the file into 4 quadrants, recursively until only a few shapes are contained in each quadrant. This minimum number can be set with the <depth> parameter of the command.

Syntax

shptree <shpfile> [<depth>] [<index_format>]
  Where:
  <shpfile> is the name of the .shp file to index.
  <depth>   (optional) is the maximum depth of the inde
       to create, default is 0 meaning that shptre
       will calculate a reasonable default depth.
  <index_format> (optional) is one of:
       NL: LSB byte order, using new index format
       NM: MSB byte order, using new index format
   The following old format options are deprecated
       N:  Native byte order
       L:  LSB (intel) byte order
       M:  MSB byte order
   The default index_format on this system is: NL

Example

shptree us_states.shp
  creating index of new  LSB format

Result

A file named ‘us_states.qix’ is created in the same location. (note that you can use the shptreevis utility, described next, to view the actual quadtree quadrants that are used by MapServer in this qix file)

Mapfile Notes

Shapefiles are native to MapServer, and therefore do not require the .shp extension in the DATA path of the LAYER. In fact, in order for MapServer to use the .qix extension you MUST NOT specify the extension, for example:

LAYER
  ...
  DATA us_states    #MapServer will search for us_states.qix and will use it
  ...
END

LAYER
  ...
  DATA us_states.shp    #MapServer will search for us_states.shp.qix and won't find it
  ...
END