GIS and database development

Abstract:

This paper describes information about GIS, Spatial or Geodatabases and a few implementations of spatial databases.

What is GIS?

Geographical Information System describes any information system that integrates stores, edits, analyzes, shares and displays geographic information. In a more generic sense, GIS applications are tools that allow users to create interactive queries (user created searches), analyze spatial information, edit data, maps, and present the results of all these operations. Geographic information science is the science underlying the geographic concepts, applications and systems, taught in degree and GIS Certificate programs at many universities.

What is Spatial or GeoDatabase

The databases used to store data for GIS applications are called Geodatabases. They are also known as Spatial Databases. A geodatabase is a database with extensions for storing, indexing, querying, and manipulating geographic information and spatial data. While some geodatabases have functions built in to allow geoprocessing, the primary benefit of a geodatabase is in the "database type" capabilities that it gives to spatial data. Some of these capabilities include easy access using standard database drivers such as ODBC, the ability to easily link or join data tables, also indexing and grouping of spatial datasets independent of software platform.

The data stored in these databases are mostly captured by images by satellites. These databases provide support storage of digital images and geometric data. The data is stored in form of objects rather than large images or other data types. These are full fledge databases with some extra functionalities included to handle geographic data.
The early implementations to store both spatial and attribute data in a database used middleware to store spatial data using a traditional data type such as BLOB, implement spatial indexing and provide a spatial query interface to applications. The IBM Geographic Database System (GDBS) in the mid-1980s used the IBM IMS hierarchical database and the IBM GeoManager in 1990 used the IBM DB2 relational database management system. IBM DB2 Spatial Extender will be discussed later in this article.
An early development in storing spatial data in a modified relational database management system resulted in a modified Oracle v.4 during the late 1980s and early 1990s; this eventually led to the creation of Oracle Spatial that is also discussed later in this article.

In the late 1990s Object-relational databases (ORDBMS) allowed geometry types to be added to additional databases. Some ORDBMSs were also extended with custom functions for the processing of spatial data using SQL. R-tree indexes allow efficient querying of the spatial data.

History of GIS Development

The origin of computer-based geographic data processing goes back to the 1970s with the development of Automated Mapping and Facilities Management (AM/FM) systems developed primarily for utilities to keep track of real world features such as pipes, transmission lines and transformers.
Initially these AM/FM/GIS or more simply, GIS systems were implemented on standalone workstations using proprietary interfaces and data representations on simple file systems. This is shown in figure 1 as First Generation. Although the spatial functionality may be sufficient for application needs, it is not an open system amenable to enterprise solutions.

Evolution of GIS Development

In the early 1990s with the acceptance of RDBMS technology and greater need for enterprise data access/sharing, major GIS vendors such as IBM, ESRI and MapInfo developed middleware products that used an RDBMS as the spatial data repository. These products provided to applications the RDBMS benefits of concurrency, data backup/recovery and client/server capability. All the intelligence for spatial indexing and geometry representation was embedded in the middleware that was constrained to use basic SQL operations and generic data types such as Integer or BLOB. A disadvantage is that applications are still constrained to a proprietary GIS API. This is referred to as Second Generation.
The customer demand for interoperable solutions not dependent on proprietary APIs and for business applications that could exploit the full RDBMS capability has lead to the development of Third Generation systems. These systems move primary data management into the database and use expanded standard SQL to operate on the data.

In recent years almost all major known database management systems have adopted the ability to store GIS related data. These systems include MySQL, Microsoft Access, IBM DB2, Oracle, Microsoft SQL Server and PostGreSQL. Following are few extensions of geodatabases.

1. PostgreSQL:

It is Object Relation Database Management System that is an Open source program. It was initially developed as a project at University of California, Berkeley in 1989. This was an extended form of Ingres database developed at the same institute in 1970’s. This database management system supports GIS data handling via PostGIS. PostGIS is also an open source software program. It was developed by Refraction Results.
The PostGIS implementation is based on "light-weight" geometries and indexes optimized to reduce disk and memory footprint. Using light-weight geometries helps servers increase the amount of data migrated up from physical disk storage into RAM, improving query performance substantially. .
PostgreSQL supports functions, triggers, indexes and user defined objects. It also introduced a method called TOAST to store large table attributes like XML messages with compression.
This system is currently in use by YAHOO, SKYPE, HI5, NEXTBUS and many others.

2. IBM DB2 Spatial Extender:

It was developed by IBM and ESRI. ESRI is a GIS modelling and mapping software technology provider. It allows to define the developer to define user defined structured types (UDT) and user defined functions (UDF). It uses R-Tree approach for indexing for better query performance.
This system is currently in use at Department of Telecommunication, City of San Francisco.
3. Oracle Spatial:
It was developed by Oracle Corporation and implemented in Oracle 7 for the first time to handle geographic data. Oracle Spatial provides a SQL schema (named by default "MDSYS", where "MD" stands for "Multi Dimensional") and functions that facilitate the storage, retrieval, update, and query of collections of spatial features in an Oracle database.
This system is currently in use at US Department of Defence - Military Home Front, USA

Conclusion:

In this article, GIS and its history is discussed with a few example of its implementations. There are many geodatabases currently in use. It is not possible to discuss all of them, but a few of those are discussed in this article. There are many others under development. GIS is now being used by every person nowadays in some way. It is the need of the time to develop fast and efficient databases for GIS.

References:

1. http://en. .org/wiki/Geographic_information_system
2. http://en. .org/wiki/PostGIS
3. IBM DB2 Spatial Extender - Spatial data within the RDBMS by David W. Adler
4. http://en. .org/wiki/Oracle_Spatial

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