Geographic Information Systems 

Intro  Techniques  Spatial  Geostatistics  Geocoding  GIS software

GIS software

GIS software is the main method through which geographic data is accessed, transferred, transformed, overlaid, processed and displayed. Various software form integral components of this interface to GIS data. There are numerous commercial, open source and even shareware products that fill these roles. Commercial software is mostly used in industry with ESRI being the leader, while government and military departments often use custom software, open source products, such as GRASS, or more specialized products. The public and small organizations generally use free GIS readers, rapidly expanding online resources or shareware.


Background
Originally up to the late 1990's, when GIS data was mostly based on large computers and used to maintain internal records, software was a stand-alone product. However with increased access to the internet and networks and demand for distributed geographic data grew, GIS software gradually changed its entire outlook to the delivery of data over a network. GIS software is now usually marketed as combination of various interoperable applications and API's.


Data creation
GIS processing software is used for the task preparing data for use within a GIS. This transforms the raw or legacy geographic data into a format usable by GIS products. For example an aerial photograph may need to be stretched (orthorectified) so that its pixels align with longitude and latitude gradations (or what ever grid is needed). This can be distinguished from the transformations done within GIS analysis software by the fact that these changes are permanent, more complex and time consuming. This a specialized high-end type of software is generally used by person skilled in photogrammetry and / or GIS processing aspects of computer science. In addition, AutoCAD, normally used for draughts of engineering projects, can be configured for the editing of vector maps, and has some products that have migrating towards GIS use. It is especially useful as it has strong support for digitization. Raw geographic data can be edited in many standard database and spreadsheet applications and in some cases a text editor may be used as long as care is taken to properly format data. Examples are OrthoEngine and ArcEditor


Geodatabases
The overall functionality as well as the very vast capabilities of GIS technology itself have grown enormously with the creation of the geodatabase. This can best be described as the latest data format to be made available in ESRI GIS software. On the surface the data appears to be the same as it did when shapefiles were the primary file type. The difference notably lies behind the scenes. Shapefiles (still functional) use .shp as one of the five sub-files that comprise one shapefile. The .shp portion of the shapefile is where the spatial component of the data is stored, and the .dbf portion is where the attribute data is stored.

The geodatabase is based on a Microsoft Access format, thus enabling end users to apply and execute different operations to the data. With geodatabases, functionality and shared capability in data editing between vector and raster data are alike. The geodatabase enables raster data to be handled as vector data. Although vector data still possesses more options in an editing process, simple .tif, geotif, and .mrsid files when contained in a geodatabase can be displayed and edited.

The geodatabase emerged with the release of ArcGIS 8.X and now includes both personal and enterprise geodatabases. ArcGIS 9.2 added "file" geodatabses.


Management and analysis
GIS analysis software takes GIS data and overlays or otherwise combines it so that the data can be visually analysed. It can output a detailed map, image or movie used to communicate an idea or concept with respect to a region of interest. This is usually used by persons who are trained in cartography, geography or a GIS professional as this type of application is complex and takes some time to master. The software performs transformation on raster and vector data sometimes of differing datums, grid system, or reference system, into one coherent image. It can also analyse changes over time within a region. This software is central to the professional analysis and presentaton of GIS data. Examples include the ArcGIS family of ESRI GIS applications (which replaced ESRI's older Arc/INFO), XMap and GRASS.


Statistical
GIS statistical software uses standard database queries to retrieve data and analyse data for decision making. For example, it can be used to determine how many persons of an income of greater than 60,000 live in a given street block. The data is sometimes referenced with postal/zip codes and street locations rather than with geodetic data. This is used by computer scientists and statisticians with CS skills, with an objective of characterizing an area for marketing or governing decisions. Standard DBMS can be used or specialized GIS statistical software. These are many times setup on servers so that they can be queried with web-browsers. Examples are MySQL or ArcSDE.


Readers
GIS readers are applications, usually free, that are distributed to allow the public to easily view maps created via a GIS, as well as view GIS-managed data. By definition, they usually allow very little if any editing of the map or underlying map data. Readers can be normal standalone applications that need to be installed locally, though they generally then connect to data servers over the Internet to access the relevant information. Readers can also be included as an embedded application within a web page, obviating the need for local installation. Readers are designed to be relatively simple and easy to use, tending to emphasize global coverage, visible light raster data and accessible vector data. Google Earth, ArcReader and GeoPDF are examples.


Web API
This is the evolution of the scripts that were common with most early GIS systems. An application programming interface is a set of subroutines (organized as object oriented programming) designed to perform a specific task. GIS API's are designed to manage GIS data for its delivery to a web browser client from a GIS server. They are accessed with commonly used scripting language such as VBA or javascript. They are used to build a server system for the delivery of GIS that is to made available over an intranet or publicly over the internet.


Mobile transfer
While not strictly a GIS application, there are applications that take GIS data and format and transfer that data in a scaled down, limitation-aware manner to PDA and GPS Receiver devices so they can be used for field applications.


Open-source GIS software
Most requirements that can be set for a GIS can be satisfied with free or open-source software. Recently an international foundation (OSGeo) was started to support and build the highest-quality open source geospatial software.

With the broad use of non-proprietary and open data formats such as the Shape File format for vector data and the Geotiff format for raster data, as well as the adoption of Open Geospatial Consortium (OGC) protocols such as Web Mapping Service (WMS) and Web Feature Service (WFS), development of open source software continues to evolve, especially for web and web service oriented applications.