karayusuf / shapefile_reader

Shapefile Reader

A Ruby library that can be used to read ESRI Shapefiles.

What is a Shapefile?

A shapefile stores nontopological geometry and attribute information for the spatial features in a data set. The geometry for a feature is stored as a shape comprising a set of vector coordinates.

Because shapefiles do not have the processing overhead of a topological data structure, they have advantages over other data sources such as faster drawing speed and edit ability. Shapefiles handle single features that overlap or that are noncontiguous. They also typically require less disk space and are easier to read and write.

Shapefiles can support point, line, and area features. Area features are represented as closed loop, double-digitized polygons. Attributes are held in a dBASE® format file. Each attribute record has a one-to-one relationship with the associated shape record.

Main File Header

Method Name	Description	Example Value
file_code	File code (always hex value 0x0000270a)	9994
file_length	Size of the file, including the header, in bytes	49915112
version	Version of the file	1000
shape_type	The type of shape contained in the file. All shapes will either be the specified shape or null. You can see the list below to see what values map to what shapes.	1
x_min	Minimum x value of all shapes	-179.14734
x_max	Maximum x value of all shapes	179.77848
y_min	Minimum y value of all shapes	71.38921
y_max	Minimum y value of all shapes	18.91112
z_min	Minumum z value of all shapes (Optional)	0.0
z_max	Maximum z value of all shapes (Optional)	0.0
m_min	Minimum measured value (Optional)	0.0
m_max	Maximum measure value (Optional)	0.0

Usage

reader = Shapefile::Reader.new(path_to_shapefile)
reader.main_file_header

Read Records

reader = Shapefile::Reader.new(path_to_shapefile)
reader.each_record do |header, shape|
  # Your code here...
end