PhpGIS
phpGIS is an OpenSource GIS application.
Geographic Information System (GIS)
The importance of geography to the workings of myriad aspects of our planet cannot be emphasized enough. An increasing number of industries are constantly in need of various geographical facts and data to make important decisions. Take for example a marketing executive trying to figure out a world-wide target audience or a manufacturer working out a global distribution network for his products. Research scientists studying the impacts of various environmental issues and their effects, as well as state heads overseeing the redrawing of a country’s borders also need to have an in-depth understanding of the geographical aspects involved.
These are just a few instances which call for detailed geographical data and material. The list of important industries that require such information is extensive as are the reasons. The most important areas include scientific research on a variety of matters, environmental impact assessments, identifications and future predictions, resource and assets management, cartography, geographic history, prospectivity mapping, urban development planning, logistics, marketing, criminology, etc.
It is to cater to this ever increasing need that Geographic Information System or Geographical Information System was developed (GIS).
GIS defined:
GIS represents an information system that compiles, integrates, edits, stores, analyzes, displays and shares spatial information about a given geographic location. The system is also considered to include all the hardware, software, procedures and personnel involved in the process.
Simply put, GIS helps individuals and industries by studying geographical locations, creating and storing tabular and attribute data related to the geographical features of that location. That data is then used to create maps and other tools that help in solving the many problems faced by the real world.
The capacity this system has for analysis is the main feature that distinguishes it and places it above regular cartography. This analytical capacity plays a vital role in the making of informed decisions in the many daily problems faced.
GIS components:
The various components of a GIS in alphabetical order include: Data, Hardware, People and Software.
Data: This is the most basic and time consuming component of a GIS system and it comes in two basic forms – spatial data and Attribute data. The former comprises, what’s known as a Geodatabase which provides spatial information about a given location on our planet. Such databases are of two types namely vector and raster. While the former makes use of lines, points and polygons, the latter is cell-based and appears as an aerial view. Attribute Data refers to all the additional information that has been got for every spatial feature of that given location. This data is stored in tabular form. To create these databases hard copies of all usable data forms such as maps are scanned and digitized which result in raster type of data. This can further be processed or vectorised.
Hardware: All the physical equipment that goes into the various activities that comprise the GIS from the collection to the analysis of data, fall under this category. Primary hardware used in the process today is a personal computer that runs the various GIS software. Other hardware include digitizers for converting hard copies of data into digital format, GPS loggers that are used for collecting data at the site and other hand held devices that are used to collect data. Web-servers are also a part of this category.
People: There are two types of people that are involved in this process. The first are those with the required expertise to create and maintain the system such as the CAD/GIS operators who “vectorise” map objects and the second comprises those people who make use of these tools to gather information or engage in analysis.
Software: It’s the software that makes it possible for all the data to be stored, analyzed and displayed. The most used GIS software today include ARC/Info, MapInfo, AutoCAD Map, etc MapInfo is often made use of for low-budget projects while ARC/Info is preferred for extensive or in-depth analysis. There are also many free GIS software in the market today such as the Free GIS Project, MapWindow, MapMaker Gratis, GRASS, BRAVA Reader, etc.
GIS Views:
When you talk about GIS the first tool that comes to mind is a map, however, there are at least two other ways in which information about a location can be viewed. Let’s take a quick look at each of these tools:
Maps: GIS maps are made following cartography however, these digital maps hold a whole lot more information than their physical counterparts. This is made possible by creating a number of layers of information for the same geographic location so that a person can make use of all or specific data about that location at a given time. This is referred to as map overlay. A user can then make use of one or more combinations of layers for their analysis. Maps can be used to find all the various locations in a given geographic location that show the same patterns or features. They can be used to identify areas based on most and least; they can identify densities; they can help people identify what exists in that location and make decisions based on that. Maps can even help us predict what changes might take place in the future, or forecast the consequences of a certain path of action, etc.
The Database: GIS can be viewed as a database referred to as a geodatabase – short for ‘geographic database.’ This is nothing but a database full of spatial information about our entire planet. In other words, it’s a geographic description of Earth.
Models: These are created because of the GIS capability to create new datasets based on existing datasets. In other words, relevant data from a given geodatabase is taken and when analyzed results in fresh geographic datasets.
What kind of questions can GIS answer?
GIS can answer questions connected to a particular location, the conditions prevalent there, the trends and patterns observed at that location, forecasts based on the information available, additional facts for that location that are not spatial in nature and lastly questions related to spatial characteristics.
Location questions provide one with information about what exists in a given geographic area. Conditional questions on the other hand seek to find areas that satisfy certain conditions. For instance, the system might be asked to point out all forested areas in the given region that are within a kilometer of a road. More than one condition can be specified. Questions aiming to identify trends in the region give rise to answers that compare the conditions prevalent in the past and the changes that have occurred since.
Pattern questions seek to find out all areas that show the same patterns. This can also be used to identify all the areas that don’t fit a given pattern. Modelling questions make use of both geographic as well as other information that has been stored for a given region to find out how certain changes if implemented can affect the area.
Aspatial questions seek to find answers that are for a given location but aren’t related to spatial data per se. For example, questions that seek to find out the average number of educated people in a given region. Spatial questions are related to the longitudinal and latitudinal location of a region. An example of such a question would be: Which GIS centers are situated within 5kms of each other.