From the course: Foundations of Geographic Information Systems (GIS)

Recreating the world on a map - GIS Tutorial

From the course: Foundations of Geographic Information Systems (GIS)

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Recreating the world on a map

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To get a clear understanding of GIS, think about how the world can be recreated in a database. That's done by converting the parts of your world, everything on it, above it, and in it. A GIS is really just a model of the world created by stacking together layers of points, lines, and polygons. A simple model is drawn in two dimensions, but a more sophisticated model can be drawn in three dimensions showing the height of buildings and other structures. It's the spatial relationship between these shapes that allows you to ask questions of your GIS. Think about a GIS that a local police department uses for public safety. In it, every street would be drawn as a simple line right down the middle of the street. This line is called a street feature. Every stoplight would be drawn as a point. How about police stations? Probably a polygon would be drawn that shows the shape of the building on the ground. There might also be a layer of polygons that represents land parcels, local parks, or school campuses. And the land parcel polygons together would be stored in a geodatabase feature class or in an older file type called a shape file feature class. Both are used quite commonly. These streets could also be stored as a geospatial web service, making it easy for web and mobile maps to access them. Everything relevant to public safety would be represented by feature classes of points, lines, and polygons. Being able to analyze data spatially allows you to report what's happened in the past, analyze the conditions that might've caused what happened, investigate ways to change those conditions and model how these changes might affect future outcomes. Suppose you notice more than the usual number of car crashes at an intersection in your rural county last month. You know that grass near that intersection gets really high and sometimes causes visibility issues. You can overlay the county's mowing schedule with the streets on your GIS map and see that the area around this intersection has not been mowed this spring, and you know there's been a lot of rain. You can request the mowing schedule be adjusted and possibly save lives with that simple change. Now that you know what the issue is, you can ask GIS to find other busy intersections that haven't been mowed and ask the mowers to prioritize those intersections. Here's a GIS map that shows how mowing is managed in San Antonio, Texas. When I click on any of the areas, I see what the mowing schedules are for this year, and because this data exists as GIS data on the web, the local police department can probably get access to it and add it to their GIS. Now that you know how GIS models the world, take a minute to consider what are the points, lines, and polygons that make up your work world.

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