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Let us look at what’s a map first. A map really is a symbolic representation of things as they exist on the ground and their interrelationships with each other. When these entities, or points and their representations are shown in a particular scale then we call that visual representation a map. The major part of the information that we get from maps is spatial. To represent these distances we need to have a scale that relates distances on the paper to the actual distance between the points or elements. The user needs to know this to obtain useful information from a map.
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What is GIS then!
GIS (Geographic Information System) creates electronic maps that give you a lot of additional information that can be attached to the elements represented on the maps. The paper maps that we are used to convey some information, but much has to be deduced by the viewer of the map. To help, paper maps use legends or a set of symbols which have a meaning attached. For example, important places may be represented by black dots. A different size of black dots can be set to mean cities/locations of different sizes. A bigger black dot would represent a larger city in area and/or population. In contrast, the cities in the GIS maps can be (similar symbolism is used, as we are familiar with them) the same sized dot, but if you query it, it would be able to show us a lot of data related to the city, its area, population, what state it is in and any other relevant data we can conceive of. It’d be possible find accurate distances between two points.
Like other information systems or databases, you query it for information. While traveling between two points you can ask where the rest areas are, where the next fuel pump is, the next restaurant or the next motel is. Besides an aid for traveling, it is not difficult to imagine other uses of such intelligent mapping. You could map the pattern of crimes in your city with the capability to query each individual incident represented on the map. If you have all the underground water supply system mapped, you can find out which valves are due for replacement next month or year. This is possible because the elements in the system representing the valves have that information attached to them while creating the map.
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What’s involved in mapping then!
There are two parts to the GIS issue. Once created, you have systems/software through which you are able to view the maps, query them for information and may use to analyze them for further information. A typical example is to find the shortest distance between two points. Since a machine is involved you could throw in additional data before the analysis. Variables such as traffic patterns, snow conditions, construction and other information can be used to arrive at an optimum route.
There are several software programs available from well known vendors such as ESRI, Autodesk and others. A common use is in those handy car GPS navigators that we use. We get our position mapped on such Intelligent/electronic maps. It is the GIS mapping that give you the information. The actual GPS data just gives your current position on the map.
The second part of the issue is creation of maps in a format that can be used by the software to get you meaningful data. One way of creating such maps would be to actually do a survey with accurate co-ordinates read from GPS devices. You also can convert accurate satellite imagery into maps. A third approach is to use existing paper maps. Once these are scanned you get an image which represents every point on the picture as a dot. However, you cannot attach any information to it and it is heavy in terms of storage needs.
All you really need for the computer to understand a line are the two endpoints and their co-ordinates. Software is used with those two points to create a line. Similarly you convert all the other types of elements too. After the information is then attached, these become the POI or the points of interest in your GPS navigation maps.