A Geographical Information System (GIS) gives the ability to merge different existing information from different sources, facilitating collaboration for creating and analyzing data. Due to these new possibilities of reusing existing data and working on collaboratively greater scale, new challenges arise.
When someone wishes to create a new information layer based on different data sets or different formats, with different terminology, and perhaps different projection, it is quite difficult to bring them together. Harmonizing geodata is a complex, costly and time-consuming task, but could be achieved by agreeing among data capturers before the work begins.
The growing recognition that once a geodata set has been created it could be used for public and private sectors (Ryttersgaard, 2001), reinforces the need to store data into databases that are made accessible for different purposes (Philips et al., 1999). This leads to the concept that geodata could be a shared resource, which will be maintained continuously.
As a result of the previous considerations, the concept of the Spatial Data Infrastructure (SDI) was developed in order to facilitate and coordinate the exchange and sharing of geospatial data (Rajabifard and Williamson, 2001), encompassing the data sources, systems, network linkages, standards and institutional issues involved in delivering geodata and information from many different sources to the widest possible group of potential users (Coleman et al., 1998). The vision of a SDI incorporates different databases, ranging from the local to the national, into an integrated information highway and constitutes a framework, needed by a community, in order to make effective use of geospatial data (UNECA, 2005).
Different web applications may be part of the services offered by an SDI, similar to most used and know functionalities that are common in any GIS software (thematic maps, buffering, spatial analysis, etc). Some services providers can also offer other GIS functionalities as Web Processing Services (WPS). These types of services are growing fastly in the SDI domain.
- Ryttersgaard J. (2001) Spatial Data Infrastructure, Developing Trends and Challenges, International Conference on Spatial Information for Sustainable Development Proceedings, Nairobi, 8p., http://www.fig.net/pub/proceedings/nairobi/ryttersgaard-TS1-1.pdf
- Phillips, A., Williamson, I., and Ezigbalike C., 1999. ‘Spatial Data Infrastructure Concepts’ in The Australian Surveyor, 44:1, pp. 20-28
- Coleman, D.J. and McLaughlin, J. 1998, Defining global geospatial data infrastructure (GGDI): components, stakeholders and interfaces, Geomatica, Canadian Institute of Geomatics, 52(2): 129-144
- UNECA (2005) SDI Africa: An Implementation Guide, 120p. http://geoinfo.uneca.org/sdiafrica/default1.htm