Gdal (Geospatial Data Processing action Library) Learning Materials

Gdal

 

Gdal is an open source grid space data conversion library under the X/MIT license agreement.

 

It uses the abstract data model to express the Supported file formats. It also has a series of command line tools for data conversion and processing.

Gdal-Overview

Gdal (Geospatial Data Conversion action Library) is an open source grid space data conversion library under the X/MIT license protocol. It uses the abstract data model to express the Supported file formats. It also has a series of command line tools for data conversion and processing.

OGR is a branch of the gdal project. Its function is similar to gdal, but it provides support for vector data.

Many famous GIS products use gdal/OGR libraries, including arggis 9.2 of ESRI, Google Earth, and cross-platform grass GIS systems. The gdal/OGR library enables the Linux-based geospatial data management system to support vector and raster file data.

 

Gdal-functional features

Gdal supports a variety of grid data formats, including ARC/info ascii grid (ASC), geotiff (TIFF), ERDAS Imagine images (IMG), and ascii dem (DEM.

 

Gdal uses abstract data model to parse the supported data formats. abstract data models include datasets, coordinate systems, and affine GEO transform ), GCPs, metadata, raster band, color table, subdatasets domain, and image_structure domain ), XML field (XML: domains ).

 

Gdalmajorobject class: object with metadata.

 

Gdalddataset class: it is usually a collection of associated raster bands extracted from a grid file and the metadata of these bands. gdalddataset is also responsible for geographic coordinate transformation of all raster bands (georeferencing Transform) and coordinate system definition.

 

Gdaldriver class: File Format Driver Class. gdal creates an object of this class for each supported file format to manage the file format.

 

Gdaldrivermanager class: File Format driver management class, used to manage gdaldriver class.

 

Gdal-OGR Architecture

Geometry: Class geometry (including ogrgeometry and other classes) encapsulates the Vector Data Model of OpenGIS, and provides some geometric operations, WKB (well knows binary) and WKT (well known text) format conversion and spatial reference system (projection ).

 

Spatial Reference: Class ogrspatialreference encapsulates the definition of projection and datum.

 

Feature: Class ogrfeature encapsulates a complete feature definition. A complete feature includes a series of attributes of a geometry and geometry.

 

Feature Definition: Class ogrfeaturedefn contains the attributes, types, names, and default space Reference Systems of feature. An ogrfeaturedefn Object usually corresponds to a layer.

 

Layer: Class ogrlayer is an abstract base class that represents a layer of elements (feature) in the data source class ogrdatasource ).

 

Data source: Class ogrdatasource is an abstract base class that represents a file or database containing an ogrlayer object.

 

Drivers: The ogrsfdriver class corresponds to each supported Vector file format. Class ogrsfdriver is registered and managed by class ogrsfdriverregistrar.