Open Source Gisopen source gis
Open Source GIS (OSGIS) is a family of GIS s oftware packages that are publis hed along with their res pective s ource code, in contras t to the clos ed-s ource model of proprietary GIS packages . Us ually, open-s ource s oftware is unders tood to be als o free s oftware, that is , the s ource code is publis hed under a free s oftware licens e with the rights to run the program for any purpos e, to s tudy how the program works , to adapt it, and to redis tribute copies , including modifications . Thes e s oftware licens es , including the licens e-free public domain, are evaluated and promoted by the Free Software Foundation (FSF, www.fs f.org) and the Open Source Initiative (OSI, www.opens ource.org). OSGIS is the general concept of Open Source/Free Software applied to GIS s oftware.
Hist o ry
Software Projects
GRASS (Geographical Res ources Analys is Support Sys tem) is the earlies t OSGIS, which reached production s tatus and s upported both ras ter and vector data. It was originally developed from 1982 to 1995 by the U.S. Army Corps of Engineers and s ince then by the international GRASS Development Team. Initially publis hed as public domain s oftware, its licens e was changed to GNU GPL (General Public Licens e; s ee www.gnu.org) in 1999, one of the commonly us ed Free Software licens es . The GPL ens ures that modified or new s ource code mus t be publis hed again under the GPL. In the 1990s , further des ktop and s erver OSGIS s oftware projects were es tablis hed in various GIS s ectors ,
including libraries (PROJ4, GDAL/OGR, GEOS, Geotools , Geos erver), Des ktop GIS (Quantum GIS, SAGA GIS, uDIG, gvSIG, ILWIS), Web mapping/WebGIS (Maps erver, MapGuide Open Source, degree), s patial SQL (Structured Query Language) databas es (Pos tGIS), geos tatis tics (gs tat, R Project for Statis tical Computing), and metadata catalogs (Geonetwork opens ource).
Organizations
In 1992, s everal organiz ations were merged into the Open GRASS Foundation (OGF) with the s cope to expand private s ector developments for GRASS, to manage members hips , and to recruit s pons ors from government, the private s ector, and academia. The s pread of GIS rais ed the need for data s haring and interoperability. With more indus trial companies joining, OGF was res tructured as the Open Geos patial Cons ortium (OGC) in 1994 with a focus on interoperability and geos patial s tandards . The increas ing number of OSGIS projects led in 2006 to the creation of the Open Source Geo-s patial Foundation (www.os geo.org), whos e mis s ion is to s upport and promote the collaborative development of open geos patial technologies , data, and educational material.
Philo so phy, Develo pment Met ho ds, and co mmunit y
Open Source in general refers to a s oftware development method where the s ource code is maintained in a public repos itory with a group of developers , often volunteers , working on it. After peer review of code s tyle, functionality, and quality, s oftware packages are regularly releas ed under a commonly accepted s oftware licens e that regulates the dis tribution terms ens uring free
redis tribution, permis s ion of modifications and derived works , and more (s ee “The Open Source Definition,” www.opens ource.org/docs /os d; “What Is Free Software and Why Is It So Important for Society?” www.fs f.org/about/what-is -free-s oftware). For the end us er, the promis e of Open Source is to receive quality s oftware at lower cos t, which is flexible, interoperable, and free of any vendor lock-in. OSGIS s oftware packages are developed following this philos ophy. Open s ource s oftware can be cons idered commercial like proprietary s oftware as it is als o us ed in commercial projects by for-profit companies offering a variety of related s ervices .
The important OSGIS s oftware packages are interoperable and follow indus trial s tandards for data exchange. The geos patial indus try has s tarted to integrate OSGIS libraries into their proprietary products to improve their interoperability capabilities . Additionally, and in contras t to dominant proprietary GIS s oftware packages , OSGIS are portable, that is , they can be operated on various computer operating s ys tems .
Open Source Gis : Encyclopedia of Geography
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OSGIS is s trongly linked to the opening of the Internet to the civil s ociety and the s ubs equent availability of collaborative development tools and means of electronic communication. Through this , virtual developer and us er communities were formed, which s trongly s upport the evolution of s oftware and its documentation. In s ome cas es , companies are als o involved, even purs uing the development as the main actor.
Funct io nalit y
The relevant OSGIS s oftware packages offer functionality comparable with proprietary GIS. As in the traditional indus trial market, general-purpos e tools and s pecializ ed applications are available. Available OSGIS libraries include reprojection s upport, optimiz ed s patial data s torage
(nonto-pological/topological, with integration in s patial SQL databas es ), and data exchange in all common and als o s pecial s patial formats . Open Source Des ktop GIS offer a graphical and s ometimes als o command line acces s to s patial algorithms , including import/export of common GIS data, from GIS Web s ervices and from global pos itioning s ys tems with s copes for ris k analys is and as s es s ment, map projections , ras ter and vector network analys is , s patializ ation, and geovis ualiz ation. Proces s ing of digital terrain model data, creation of flow maps , geocoding of raw data, map generaliz ation, terrain analys is , views hed analys is , as well as map algebra are s upported. Vector data can be generated through digitiz ing from s canned paper maps or through vectoriz ation of ras ter data; s ome OSGIS als o s upport the analys is of topological relations hips . Geos tatis tics are either found in dedicated s oftware
packages or through dedicated GIS interfaces to s patial clas s es of s tatis tical s oftware, which directly read from the GIS databas e. Further functionality includes image proces s ing with data extraction from LiDAR (light detection and ranging) and airborne las er s canning, analys is of microwave/RADAR (radio detection and ranging) data, multis pectral imagery, multitemporal imaging, s tereos copy and
orthoimagery, and s upervis ed clas s ification of aerial and s atellite data. Reduced and optimiz ed s oftware packages are available for mobile GIS.
Open Source Internet GIS is provided as pas s ive Web-mapping applications or as interactive WebGIS with the capabilities of a Web proces s ing s ervice.
For OSGIS metadata management, dedicated catalog s ys tems are available, which operate as online metadata harves ter and retrieval s ys tems . They acces s and lis t s patial data hos ted in-hous e or in remote but Internet-acces s ible databas es through s pecializ ed protocols for metadata exchange. Markus Neteler
Furt her Readings
Mitchell, T. (2005). Web mapping illustrated: Using open source GIS toolkits. Sebas topol, CA: O'Reilly. Neteler, M. , & Mitas ova, H. (2008). Open source GIS: A GRASS GIS approach (3rd ed.). New York: Springer.
Ent ry Cit at io n:
Neteler, Markus . "Open Source Gis ." Encyclopedia of Geography. 2010. SAGE Publications . 2 Oct. 2010. <http://www.s age-ereference.com/geography/Article_n845.html>.
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