What You Can Do with a Geographic Information System (GIS)
A GIS is not simply a computer system for creating maps. In fact, a map is simply the most common way of reporting information from a GIS database. A GIS is an “information system”. These systems are not just the software and hardware, but also, and most importantly, the collection of information (the database) about where geographic features (roads, buildings, fire hydrants, pipes, crime incidents, ponds, streams, etc.) are located in your community. Building this database involves compiling the information from maps and aerial photos, card files, people’s personal experience, or existing computer databases. A GIS database integrates all this information so that it can be used together and is accessible through a single computer, typically a personal computer (PC).
In addition to making maps and maintaining the database, GIS also makes it possible to ask questions that are typically difficult to ask without a computer:
- Where are the properties where the assessed value increased? Decreased? Is their value consistent with those of similar properties in the neighborhood?
- What vacant properties are larger than 100,000 square feet, are zoned commercial, and are within a half-mile of the interstate interchange?
- What school students are eligible for bussing based on their distance from the school?
- What properties above a certain elevation will be affected by shutting down this water tower for maintenance?
- Given requirements for response time, which is a function of street distance and driving speed, what is the best location for the new fire station?
- Is there a spatial pattern (clustered location, time of day, how the crime was conducted) in the recent outbreak of house burglaries?
In addition, a GIS can be used to automate routine tasks. Sometimes the capabilities for performing these tasks (“applications”) will be “built-in” to the GIS software; often they will need to be developed using programming capabilities provided with the GIS software. Increasingly, “standard” GIS capabilities are being extended to include the more common applications in specific market sectors. Similarly, some consultants have applications that they sell and then install on your system and customize for your site. What will be true of your GIS will depend on the software you buy.
The GIS uses described below are typically activated by using a computer mouse to “point and click” on menu lists and other graphic objects that appear on a computer screen. Knowing what to click on is part of learning how to use the GIS. The actions selected with the mouse result in software programs performing the selected task. In other words, the only typing the user has to do is entering information requested by the software.
Some of the ways GIS is being used in Massachusetts communities include:
- Tax (Parcel) Map Maintenance – As property boundaries change, the Assessor’s tax maps need to be updated. Once property boundaries are part of the GIS database, they can be edited using the GIS software. These edits show up on the system the next time a map is printed or the next time the edited location is viewed on the screen; this means that the GIS users see updated information more quickly than they would if they had to wait for periodic updates of their paper copies of these maps.
- Producing Mailing Labels for Abutter Notifications – Zoning board of appeals hearings or proposed actions by a town/city require notifying abutting property owners. A GIS application for producing abutter mailing labels enables you to identify abutting property owners in different ways (“within 300 feet”, “abutters and abutters-to-abutters”, “abutters on a Main Street between house numbers 23 and 77”). Once the properties are identified this kind of GIS application can produce mailing labels and be integrated with a word processing “mail merge” capability.
- Standard Theme Maps – Many communities produce or need maps for specialized purposes (e.g., snow plowing route maps, property maps for revaluation by the assessor; atlas maps of the water system; police beat maps, zoning maps, etc.). A GIS typically includes a programming capability that makes it possible to create a standard map set. When the program is run it produces one of each sheet in the set and sends them to a color printer.
- Custom Maps - Once your GIS is developed, you will see an explosion of map-making. This will occur because a GIS allows you to make maps of virtually any size and scale for any area of your jurisdiction. In addition, these maps can combine any set of features you want from the database. This is simply not practical without a GIS.
- Determining Conformance to Spatial Criteria for a Building Permit - The GIS software can help the viewer determine whether or not a requested permit is in an historic district, an aquifer protection district, wetland, or floodplain. Similarly if a proposed license or permit is for an activity only permitted in specific areas (adults only retail/entertainment establishments; wireless communication facilities), GIS capabilities make reviewing those criteria much quicker.
- Providing Basic Information for A Building Permit - At its simplest level this involves using the GIS to find a property location using an address. Once the property to which the permit applies is identified, the GIS can be used to provide some of the essential information (e.g., address, property ID, zoning classification, lot area, street frontage) needed for filling out the permit.
- Public Access Terminal – GIS can be used at public counters, either by the public or by town staff assisting the public, to view information such as properties and related information about assessed value. Similarly information about streets, open space, natural features, school districts, election wards, or zoning districts can also be displayed. If provided, such a terminal might also enable users to make maps of the requested information.
- Network Infrastructure Maintenance Tracking – Your public works department may systematically and annually perform certain kinds of maintenance on road, sewer, water, or storm drain networks. These actions might consist of street re-paving, water main flushing, or similar activities. A GIS could be used to track work that has been performed in prior years, the work planned for the current year, and the work proposed for future years. This information can then be summarized on a map and/or in tabular form.
- Export Data to Computer Assisted Drawing (CAD) Software – Your GIS software will be able to export your data to other file formats. These commonly include .DXF, or drawing exchange format. This format is read by many software packages including the CAD software AutoCAD. This kind of application might allows you to select features (e.g. property boundaries, building outlines, sewer pipes) for an area you select and then save them to .DXF file format for use in creating engineering design drawings.
- School Re-Districting – Communities regularly have to tackle re-districting their school boundaries as the student population shifts, or as new schools are opened or existing schools closed. If you have locations, typically using an address, for all the students in your schools, a GIS makes it much easier to evaluate possible re-districting scenarios. You enter a proposed boundary modification and the GIS can then tell you what the student counts are, by grade, with the new boundary configuration. While school departments have been doing this for years, GIS software makes it possible to evaluate proposed boundary changes much more quickly.
- School Student Walking Distance Analysis – If your community busses students to school, but only if they live beyond a certain distance from their school, a GIS can be used to determine what addresses are eligible for bussing. Also, if your GIS contains property boundaries and school boundaries, you can develop a database that tells you, for each address in the school district, what school (elementary, middle, and high) a child attends, whether they are eligible for busing, and whether they live in a “school choice area”.
- Fire Equipment Response Distance Analysis – A GIS can be used to evaluate how far (as measured via the street network) each portion of the street network is from a firehouse. This can be useful in evaluating the best location for a new firehouse or in determining how well the fire services cover particular areas for insurance ratings.
- Buffers Areas Where Extra Penalties Apply for Drug Sale Convictions – If you are convicted of selling drugs within a 1000 feet of a school property, special penalties apply. GIS software can readily create and display /map these buffer zones making it much easier to determine whether a specific arrest location is within the buffer zone. A similar capability can be used for determining whether a proposed land use is within a specified distance of a school or religious institution (e.g. adults only retail/entertainment establishments).