What is PostGIS, and how is it used? Let’s take a look at the basics of this tool, how it is used by a major mapping group, and how to seamlessly adopt it yourself.
- PostGIS – What Exactly Is It?
- Case study – Institut Géographique National
- Fast Access to PostGIS
PostGIS – What Exactly Is It?
GIS stands for geographic information system. This type of software is used to organize a dataset via geographical components so you can see the information within space. Essentially, you can request data from a database and have the information presented as a map. This tool may initially sound like it’s only useful for special cases, but datasets often contain critical geographic components, explains Margaret Rouse in TechTarget. Sample applications include meteorology, understanding sales volume in various regions, population assessment, and land-use analysis.
PostGIS is an open source geographic information system that can be used with the object-relational database PostgreSQL to support geographic objects.
PostGIS owes its wide adoption in part to following a standard recognized within the mapping industry – Simple Features. Simple Features is standardized as ISO 191255 in collaboration between the International Organization for Standardization (ISO) and the Open Geospatial Consortium (OGC). It delineates a manner in which primarily two-dimensional data such as points and lines is to be stored and retrieved.
It is also popular because of its relationship to PostgreSQL, which is an enterprise-class open source database that has actually won a few awards. “PostgreSQL has won praise from its users and industry recognition,” explains the official website, “including the Linux New Media Award for Best Database System and five time winner of The Linux Journal Editors’ Choice Award for best DBMS.”
First made available in April 2001, PostGIS works with Mac OS X, Windows, and Linux. Most recently released on October 7, 2015 (Version 2.2 .0), PostGIS is refined by various contributors and offered openly with the GNU General Public License.
Case study – Institut Géographique National
The Institut Géographique National (IGN) is a national agency in France that employs 1800 people to manage and control geographical data.
IGN determined in 2002 that they wanted to switch from their desktop GIS program, GeoConcept, to a uniform database that would not require defining a specific tile for management.
The three systems that IGN explored were PostGIS/PostgreSQL, DB2, and Oracle. Their chief concerns were that the GIS would be able to support over 100 million objects, to maintain great speed, and to offer strong data integrity. The agency used benchmarking studies to look at the performance of PostgreSQL/PostGIS vs. the proprietary options, and the results were compelling.
One of the people at IGN who helped to decide on PostGIS is project manager Frank Fuchs. “Since PostgreSQL and PostGIS are free and open source software, we could use them quietly in a prototype,” he says. “On the other hand, if we used a commercial DBMS, we could later have a problem in a call for tenders.”
Fuchs and his colleagues are using PostGIS with France’s “BUDni” database, which is a three-dimensional database of the country that includes transportation routes, buildings, bodies of water, and jurisdiction designations. The group created a new method to manage the data seamlessly, integrating the new system into the software that was already in use by the agency’s personnel.
IGN decided that they wanted PostGIS for the backend but also wanted to keep GeoConcept as an interface for editing the data. GeoConcept was adjusted to manage the flow of information in and out of the primary database:
- A data loader simply takes a GeoConcept file and puts it in the PostGIS database
- A data extractor grabs data from the PostGIS database and moves it into GeoConcept to be edited.
- A data synchronizer sends updates from client devices to the central database and vice versa.
Since IGN is using the GeoConcept GIS to edit, analysts working for the agency don’t need to be updating the system all the time. Rather, their device can synchronize with the main one whenever a connection is possible. Analysts also don’t have to be trained in a new technology because they are still using GeoConcept. The extractor and synchronizer rely fundamentally on the PostgreSQL transaction system so that data integrity is maintained if there are ever connectivity issues – such as the system going down during synchronization.
Finally, since reliability and integrity are paramount to the Institut Géographique National, a redundant backup server is synchronized to the primary server every few hours.
Fuchs is impressed with PostGIS, especially its transactional capabilities. “Remember that databases are very powerful tools, and transactions are a key feature,” he says. “PostGIS brings these tools to the GIS community very efficiently.”
Fast Access to PostGIS
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