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Quantum GIS Software: Application User Review

Product Name: Quantum GIS (QGIS)
Home Page: http://www.qgis.org
Version: 0.11.0, July 2008
Operating Systems: Linux, Unix, Mac OSX, Windows
Cost: Free; for download visit http://download.qgis.org/downloads.rhtml

Quantum GIS is an open source Geographic Information System that supports most geospatial vector and raster file types and database formats. Unlike many other open source GIS programs, QGIS is available for a number of operating systems, including both Windows and Mac OSX. The program offers standard GIS functionality, including a large variety of mapping features, data editing, on-the-fly projection and GRASS digitizing. Its support for plugins expands its functionality further by providing additional tools such as GPS data support, georeferencing, and additional mapping elements.

Specifications and Installation:

Licensing

    QGIS may be used free of charge or redistributed to others as granted under the GNU General Public License.

Platform

    Linux, Unix, Mac OSX, Windows

Supported File Formats

    Reads Raster Image Files
    Arc/Info binary/ASCII Grid, GRASS, GeoTiff, USGS ASCII DEM, Erdas Imagine

    Reads Vector Files
    Most files that are supported by the OGR library, including ESRI shapefile, MapInfo, SDTS and GML.

Help

There is an excellent comprehensive up-to-date 177-page user guide (2.9 MB PDF) with full-colour illustrations that was written for the application user as well as the application creator. The user guide includes an introduction to GIS and an overview of all the features and functions of the program. For those wishing to use the source code, the documentation offers details for the different supported operating systems. There is also a comprehsenive workshop package available from the website that covers all the essential features and functions of the program. QGIS also offers an FAQ section on their webpage which answers a wide variety of questions and problems.

Installation

A quick and simple download is available from the QuantumGIS download page: http://download.qgis.org/downloads.rhtml. There are currently three versions available for download, the most recent being version 0.11. The application is approximately 70 megs in size.

Functionality

Introduction

Quantum GIS offers many of the common GIS features and utilities necessary to view and edit data and to generate a map : zooming, map scale, legend panel, layer appearances (colors, symbols, etc.), thematic mapping, labelling, measuring (including area), and more.

  • Readily works with data in multiple formats (SHP, KML, TAB, TIFF)
  • View and query attribute tables
  • Conduct spatial queries
  • Create new layer
  • Edit, delete layer
  • Generate maps
  • Print, and export maps

Creating Maps

An essential feature of any GIS software is the ability to create and display a map with many of the fundamental cartographic elements - legend, scale, north arrow, context map inset, title, and citation. When selecting a GIS software program, one of the central features to look for is the capability to create maps.

QGIS will display both raster and vector data simultaneously, and offers several customizable appearance-related features. Raster datasets can be altered by changing the band settings but also by modifying the symbology properties. One can change between colour and grayscale, invert the colour map, set the transparency for the raster as well as adjust the settings for a grayscale image.

Vector data can be symbolized and coloured with a number of choices. Data rendering includes Single Symbol for displaying features in the same way; Graduated Symbol symbolizes features based on a number of different classes; Continous Colour renders a numeric field which displays its minimum and maximum results; Unique Value classifies features by unqiue category.

The labelling feature appears to be an all-or none utility. The user can turn the labelling feature on for any of the layers and this will label every feature on the map. There does not appear to be an option to label only certain features and there is no text or symbol insertion available either. When using the labelling feature, the user can customize the positioning, size, colour, and font. Label appearances can also be defined by feature parameters.

Equally as important as map creation functionality is the ability to export or print the map or screen view. The user has a couple of image export options. One can save just the map screen view as a PNG or JPG, or the map ouput with cartographic elements included. There is no option for user-specified resolution so the end product is only available in default quality. The final map includes basic cartographic features such as scale, legend and title. The scale text does not read properly however until the units are defined in the application properties, and the legend does not offer the user any display customizability (background colours or borders). Additional features such as north arrow are available only with a Plugin. The user has a choice in the location of the cartographic elements (text, and legend), and the final product is free of QGIS insignia labels and watermarks. The user has a limited number of image formats to select from to save the map output – BMP, PNG, PPM, XPM, and XBM. The application however does not support any georeferened image formats such as GeoTiff or GeoJpg. Image export is available from the Print menu and requires several steps before the image can properly be saved. Offering a map image export option from the File menu would prove to be more user friendly.

Printing and exporting unfortunately does not include the attribute table nor the database file and therefore tabular information cannot be exported in any way.

Figure 1 : A map created with QGIS

Querying, Digitizing and Editing

Users have the opportunity to perform both simple and complex queries. One can filter or query for records within the attribute table by performing searches. Custom queries can also be generated and the use of the SQL query builder will allow the sophisticated combination of spatial selection and attribute query using multiple criteria.

An advanced feature of QGIS is the ability to create Shapefiles. The user has the option to create points, lines and polygons very quickly and easily. The user can also edit any shapefile spatially (modifying vertices) as well as editing the content in the attribute table.

Expanding Functionality with Plugins

QGIS includes twelve plugins that enhance and extend the application. They include

  • Delimited text import
  • Copyright lable
  • Graticule builder
  • North arrow
  • Scale bar
  • Copyright label
  • PostGIS import tool
  • Plugin installer
  • Mapserver export
  • Raster georeferencing
  • GPS tools
  • GRASS
  • WFS

Although these plugins are considered to be additional enhancements, many of the features that they support are actually standards in other GIS programs. Delimited text import for example allows users to import text files with X and Y coordinates to display as points. The north arrow and scale bar are also basic additions that should be available without the additional effort of installing the plugins. Some plugins that do in fact provide advanced features include the raster georeferencing, since very few open source programs offer this, as well as the GPS point tool. The WFS plugin is another excellent feature that other applications are beginning to invest in.

Usability

The features of QGIS are easy to work with and a simple map can be generated quickly. Some of the more complex features such as thematic mapping and querying take more time to understand, and learn to successfully apply it. Some of the more basic features that GIS users would expect are surprisingly not available, such as text or graphic insertion, custom labelling and any image-related manipulation (clipping) or high resolution image export. However, for a free program it is remarkably sophisticated with some very valuable GIS tools. What stands out the most about this program is its editing tools – the ability to easily create, edit and delete shapefiles and files within it. The raster georeferencing plugin is also a remarkable feature. QGIS would satisfy any GIS user who is in need of viewing and manipulating geospatial files in a variety of formats, and is interested in creating simple maps with these datasets.

- Published November, 2008


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