Section Four - Putting it all Together: An Example
In the last section, we looked at an example from a television show where a mathematician used GIS to solve a series of crimes by locating the criminal based on patterns of movement and behavior. While GIS is indeed used in crime analysis, that kind of sensationalized GIS only really happens a tiny fraction of the time. In reality, GIS is less dramatic, solving important problems indeed, but usually with less intense stakes. We use GIS in so many areas, understand patterns and make decisions for the growth of businesses, understand migratory patterns of different species, analyze suitable habitats for flora and fauna, and examine logical changes in municipalities. This example is just one of so many that we could present here, but it's a solid one in understanding how city, county, state, and federal governments decide where to place new structures and services. Most likely, you've never thought about how the location of an ambulance bay is decided. You may have noticed one going in but have only had the singular thought "Oh, look, they are putting in a new ambulance bay." In contrast, the placement of it, and other community services, is not random at all but a carefully constructed and well-thought-out science.
The problem: You are a City Planner of a major city. You’ve been given one million dollars (Dr. Evil voice) by the mayor to build a new ambulance bay for the city, which will be in addition to the three existing ambulance bays. You’ve also been instructed to put it in the most underserved area of the city and not to mess up or it’s your job (Apparently, this mayor isn’t very nice).
So, following the GIS model, you begin collecting representative data (as the reality is there is a need for a new ambulance bay in the city, and the conception is the map will show several suitable parcels to build the new ambulance bay).
The spatial data you will need includes:
- a parcel layer (a GIS layer that shows the boundaries and ownership of all the properties within a city or county)
- the known locations of the existing ambulance bays
- a layer showing streets
- a layer showing the stop signs and signal lights at all of the intersections in the city
And the non-spatial data includes:
- which parcels are owned by the city and are or could be vacant
- the speed limits of all the streets
- known traffic patterns, including the most and least congested times of the day
- the number of calls the three existing bays receive per day
- what time of day those calls are made
- the duration in time from when the ambulance receives the call until they arrive at the patient's location
- the duration of time from loading the patient on the ambulance and arriving at the hospital
- the average age of the patients
- the average age of the city by census block
Using GIS, you are able to accomplish several tasks:
- isolating and extracting only the parcels which are owned by the city and are vacant or could reasonably be vacant. This information tells you the possible locations the new ambulance bay could be built. Just because the other spatial analyses place the new ambulance bay on the corner of 1st and Lincoln doesn’t mean that there are any suitable parcels at or near that location. There is a limitation of construction by parcel.
- locating parcels where the old and young reside. Statistically, families who take care of young children or elderly parents call the ambulance more often than families consisting of members in their late teens through mid-forties. Placing an ambulance bay downtown in the hip, young area does not serve the local population as well as placing it where retirement homes or daycares are located. However, like all things in GIS, there is no perfect location, nor do families of equal age live near each other exclusively. We are limited to statistical generalizations.
- the patterns of speed limits and traffic, as well as the locations of stop signs and signal lights. Speed limits, as we know, do not always mean that the flow of traffic on that street is equal to the posted number. Many times, streets can move faster or slower than the posted limit, generally depending on the time of day. Morning and evening are generally more congested than other times of the day, and cars often can't (or don't) move out of the way of an ambulance driving with its lights and sirens. These factors absolutely come into play in the planning of a new ambulance bay.
- the response times from the existing ambulance bays. When the goal is to find the underserved area, it's important to find the areas on the map where it currently takes an ambulance the longest to respond. When initial emergency care takes a long time to arrive, the chances of survival begin to fall exponentially, depending on the illness or injury. With that logic, it's obvious that having more ambulance bays throughout a city would improve life-saving efforts, even if the patterns of data do not show that said ambulance bays are not spread out evenly based solely on distance.
- the number of calls per ambulance bay. When you know the traffic for a bay, you know how much work is expected of each one, and when you examine the change in age demographics (as the average age of an area is a variant factor).
Through GIS analysis (the fourth step in the GIS model), we can create new data layers by extracting the information we need from the information we have, thus cutting down on the visual "clutter," and in a similar fashion to the crime map in the "Numb3rs" example, we can lay out the information on a city map attempting to find a pattern in the data. When we examine the spatial patterns created by the data, we can locate and answer questions such as "Where, consistently, are areas that are seeing response times double those of other areas due to factors such as heavy traffic or long travel distances?", and "Are there any areas where long response times overlap with an aging population pocket?". After we locate areas that may be suitable for a new ambulance bay, we can even use GIS to model travel times from several new locations without even leaving the office! Once you've determined a suitable location or two, you can use GIS to create an output map that can be placed into a PowerPoint presentation or a Word document to report your findings back to the Mayor, who gives you a medal for doing such an amazing job at serving the community!