What is GIS
GIS stands for Geographic Information System. It’s a computer-based system designed for storing, analyzing, updating, manipulating and displaying spatial data. GIS can be viewed from 3 perspectives-the map, the data and the spatial analysis.
The map view focuses on the ability to create and present information in a cartographic manner. This enables the presentation of information in a visual manner and assists in building user knowledge.
Data is an important component of GIS. It provides users with a tool to capture, manage, query and analyze data from various sources. There are 2 different components of data stored in GIS.
- Component which defines location a spatial component such as:
points- discrete features ie, a tree, building, traffic sign
lines - connected locations ie, roads, rivers
areas - which have length and width ie, lakes, perimeter of a building etc.
A descriptive component describing the feature ie, length of road, height of tree etc.
The power of GIS lies in its ability to identify relationships between features based on their locations and their attributes. GIS also allows one to view these relationships in maps, charts, tabular forms etc. In GIS one has the ability to create different layers of data. For example, one can create layers for roads, traffic signs, accidents, buildings, fire hydrants, water lines, etc and once the layers are created one can superimpose different layers and analyze the relationship between various features and their attributes. For example, if one wants to repair a pothole, one can quickly turn on the layer for potholes, roads and water lines and determine if repairing the pothole would entail digging the road under which a water line is running.
In order to analyze the data one requires relevant and current information, which can be obtained from various sources. Some data can be obtained from existing sources eg population, census, roads etc. However, other data specific to a project may not be readily available and may have to be collected for a specific project with GPS. Once the data is collected in GPS receivers, it can be directly transferred to a GIS System. This data will have the spatial location as well as feature/attribute data attached to it.
Integration – GPS/GIS Technology
GPS is a powerful tool providing a unique position of a specific feature. With this information, one can navigate back to it. However, one cannot relate this “feature position” to any other “feature position” unless one is standing at the site and other features are visible.
GIS by itself provides great analysis capability but to achieve that one needs plenty of good data. As explained earlier, some data is available but a lot of other data needs to be collected to allow the full capabilities of GIS to be utilized.
Combining the GPS data with GIS allows for greater capabilities than what GPS and GIS can provide individually. With the combination of two technologies one is able to display the “FIELD/ACTUAL SITE” on a PC and make informed decisions. There is no need to make specific site visits or review several documents/drawings. Also, another benefit of the integration is the fact that the data can be shared by unlimited users in various departments for their own specific needs and analysis.
Another important advance in this technology has been the introduction of a software which allows bringing into GIS not only GPS position information but a digital picture. With this software, one can study relationships between features but also view actual photographs of the features right on your PC.
Figure 1 shows chemical discharge points obtained with GPS. In GIS software they appear as points with XY positions.
Figure 2 shows same points superimposed on map of waterways (obtained from existing sources, Texas Rivers.shp). Now one can visualize the close proximity of some of the hazardous chemical discharge points to waterways.
Figure 3 shows above but with roads (obtained from existing sources, Texas Roads.shp) and now one can relate the existence of chemical discharge points in relation to waterway & roads.
Figure 4 shows all of the above but with population density and now one can observe the potential impact of accidental chemical discharge on population.
One can keep on adding “layers” of data and visualize relationships between chemical discharge points and other features.
One can start asking “What if” questions once the data is displayed. For example, one can ask, “Which waterways or how much population will be impacted by a accidental chemical discharge from a specific point?”
- Figure 5 shows cultivated land and wildlife sanctuaries - data collected by GPS.
- Figure 6 shows the points superimposed
with waterway layers.
Figure 7 shows the above with the flood layers displayed and this indicates which cultivated lands and sanctuaries may be impacted by the floods.
One can decide by looking at this map which areas are prone to flooding and therefore not suitable for wildlife sanctuaries and agriculture.
Figure 8 shows a background of roads (obtained from existing sources, Roads.shp).
Figure 9 shows a new layer of “Pot holes” generated by GPS.
Figure 10 shows existence of pipeline along the roads.
Just by looking at this map one can see the potential of damaging the pipeline by the crew digging around the potholes to fix them.
In all the above examples, one has been able to display the maps on the computer and ask “What if” questions. There has been no need to go and visit specific sites to analyze this data. One does not have to visit the site in cold or hot weather, be too close to traffic/ wildlife, scribbling notes on pieces of paper. Integration of the 2 technologies brings the “actual site” on to your PC and allows one unlimited analysis capabilities.
Pitfalls of Integration
Combination of GPS/GIS technology is limited by the amount of data. As explained earlier one needs lot of good data for conducting analysis. While some data is available, a lot of data has to be generated by the users for their use. Sometimes collection of field data could turn out to be time consuming and expensive.
Data collected must be accurate and meet the correct formats. For example one needs to make sure that all the “layers” of data displayed are in same units (feet/meters) and the projections and datums match. Without this the analysis will not be correct.
The integration of GPS with GIS brings the real world to the desktop. What could take days to visit a specific site and analyze can now be performed on your desktop. The power of GPS/GIS is immense and application are unlimited and varied in all areas such as agriculture, environmental, defense, natural resources, health, business etc. As the price of hardware and software comes down I see the potential of this integration to grow tremendously in country like India.