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A. Deva Kumar Varma
GIS Engineers Society,
Organizations spend thousands of dollars in the collection and compilation of spatial data. To reduce overall costs, effective data sharing among the organizations is widely recognized as a strategy – one with the side effect of enhancing organization’s operational efficiency, effectiveness, and decision-making ability.
This philosophy underlies the new paradigm that is rapidly taking shape with the growing adoption of GIS technology by large organizations. Though it goes under different names, by far the best suited is Enterprise GIS (E-GIS). The key concept underlying Enterprise GIS systems is data sharing, unlike in traditional systems where the views varied from reluctance to almost a taboo. Emergence of such systems reflects a major shift in management perspective regarding data related issues like sharing, ownership, custodianship, etc. In an enterprise environment, data plays an important role. An introduction to configuration and implementation of spatial databases is presented in this article. Since the focus is more on practical aspects rather than a theoretical treatment, the discussion is based on ArcSDE software, part of the ESRI ArcGIS family of software products, widely used for implementing enterprise spatial databases.
Enterprise GIS Systems
An Enterprise GIS system in reality is an aggregate of three subsystems viz., mapping, spatial analysis, and data management. E-GIS systems differ in scope and services from that of a traditional one. Under traditional environments system downtime, or its poor performance, is not critical to the enterprise’s business. But, GIS Systems at the enterprise level support its core business and any downtime or performance issues can be critical affecting the enterprise’s business.
Enterprise Spatial Database
Enterprise spatial databases tend to be centralized and grow rapidly. Spatial database environments of the 1990s with 10 – 20 GB vector data have now grown to over 100GB, while the raster have grown from 100-200 GB to several terabytes in the same period. To provide data to many hundreds of users at performance levels reasonable enough to do their business at all times is a potential challenge even to a skilled GIS professional. It is here the importance of configuring and managing an enterprise GIS database assumes significance.
For delivering successful E-GIS database solutions one of the preferred candidates around the world is ArcSDE software. Though many have heard of ArcSDE not all might have had the opportunity to use it, or even less, utilize to implementation an Enterprise-GIS database.
ArcSDE is an application server that facilitates the storage and management of spatial data (raster, vector, and survey) in a DBMS. Spatial data managed by ArcSDE in a DBMS for an enterprise is called an Enterprise Geodatabase. A Geodatabase – short for geographic database – simply put, is a series of standard DBMS tables, indexes, etc., which works in concert with higher-level logic resident in the application tier to support geographic analysis and display functions. At the moment, ArcSDE supports four commercial databases IBM DB2, Informix, Microsoft SQL Server , and Oracle .
ArcSDE brokers all types of database transactions for GIS clients. It does the job so nicely that GIS happily ticks away oblivious of DBMS flavours that host the spatial data. This single feature enabled GIS to pull down barriers to spatial database integration and leverage the existing IT infrastructure. E-GDB is preferred by enterprises due to its ability to integrate and leverage their IT infrastructure.
E-GDB may sound prohibitively expensive to some, in terms of hiring and maintaining staff with expertise in ArcSDE / DBMS.
In such cases, there is a simple solution, use the free ESRI software “ArcSDE for Coverages”. It is easy to implement and makes your transition to ArcSDE as painless as possible. Space constraints limit this discussion to ArcSDE, interested readers may refer ESRI documentation.
ArcSDE Storage Model
Before proceeding further it is prudent to have some basic understanding of how ArcSDE stores spatial data in the geodatabase (GDB).
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