Leveraging GIS Data for Faster Responses

Contributed by Britt Wollenweber, GIS manager at Tyler Technologies

When a call comes in to 9-1-1 emergency services, dispatchers work quickly to send the fastest response possible to those in need. What many people don't realize is that response times are greatly impacted by the geographic information systems (GIS) mapping capabilities of each public safety answering point (PSAP).

Mapping capabilities are used by all PSAPs with computer-aided dispatch (CAD) systems to send an emergency response to a call for service (CFS).

This is how it happens.

As soon as a voice call to 9-1-1 is answered by dispatch and the caller states his or her location, that information is entered into the CAD system by the dispatcher. When the address is entered into the system, it is automatically geocoded, which is the act of turning an address into a specific location on a map using latitude and longitude coordinates. These coordinates verify the address and show dispatchers which police, fire or EMS units are assigned to that geographical location.

Additional GIS data is necessary depending upon whether a PSAP uses area-based or proximity dispatching.

With area-based dispatching, police, fire or EMS units are assigned to a CFS based on the location they are assigned to within the community. In a community with area-based dispatching, when a CFS comes in to a 9-1-1 communication center, dispatchers send the available police, fire or EMS unit assigned to the specific area the call came from.

Proximity dispatching takes area-based dispatching to the next level by sending the closest police, fire or EMS unit to a call for service regardless of the unit's beat, jurisdiction or coverage area.

Public safety agencies that stay abreast of current technology use proximity dispatching to ensure responses are faster.

Automatic Vehicle Location: The Key Difference in Dispatching Capabilities

Automatic vehicle location (AVL) functionality is what takes proximity dispatching to the next level as it allows dispatchers to see where police, fire and EMS units are in real-time on a digital map within the CAD software. PSAPs solely using area-based dispatching do not have AVL functionality.

Agencies using AVL equip police, fire and EMS units with global positioning system (GPS) devices that constantly track and send a unit's latitude and longitude coordinates from the unit back to the CAD workstation located in the PSAP. To do this, the mobile data terminal (MDT) located in each unit receives the GPS signal and automatically transmits that signal back to the dispatcher's CAD system.

This allows dispatchers to know where all units are at any given time and provides them with continuously updating estimated time of arrival (ETA) information. It also allows first responders with MDTs to see units on their maps, which aids in increasing a first responder's situational awareness out in the field.

AVL also fits the unique needs of each community as it can be preconfigured by an agency's GIS administrator to account for height and weight restrictions, road closures, detours, temporary road blocks, and other events which could impact a response.

For instance, if a community has numerous one-way streets, old bridges, dirt roads or low underpasses, this information can be programmed into the CAD system and response plans so that units that shouldn't travel on these roads are never routed down them.

As long as an agency maintains accurate GIS data, dispatchers using AVL are able to route first responders as accurately and quickly as possible to a CFS.

The Use of GIS Data in Area-Based and Proximity Dispatching for Accurate Responses

Up-to-date GIS data is crucial for both area-based and proximity dispatching as an address is geocoded as soon as it is entered into the CAD system by a call taker or dispatcher. What happens next depends on if a PSAP is using area-based or proximity dispatching.

An area-based response takes three key GIS components into consideration: address points, lines and polygons.

An address point is the latitude and longitude location of a known address, such as a residence or business. Lines represent streets throughout a community. A polygon is a shape a GIS administrator can create using connected lines that he or she draws to identify a specific area. Polygons are created to identify specific areas that encompass a large area such as a body of water, neighborhood, school, shopping center or park.

Dispatchers use address points, lines and polygons to accurately route units to a CFS. They do this by entering the location into the CAD system and then using the address point to plot the location of a call. Line information is used to determine how first responders will get there and how long it will take based on distance alone. Polygons are used to aid the dispatcher in visualizing the specific area where a response is located.

Beyond this geographic data, dispatchers using area-based dispatching assign units to a CFS based on the area in which that unit is assigned.

For example, if police dispatchers receive a CFS and five rescue units are located in a specific beat, but only one is available when a call comes in that falls under that beat, dispatchers will send the one available unit to the call for service.

With proximity dispatching, once dispatchers have determined the location of the CFS, they will send whatever unit can respond the fastest, whether they were pre-assigned to that specific area where the CFS came from or not. They do this by seeing the units on the digital map using that information to determine which is closest to the CFS.

GIS data is required to view the unit's continuously updated ETA and account for any map events such as roadblocks, detours or temporary closures on the roadways.

Both forms of dispatching require accurate GIS data, which is why it is important for a PSAP's GIS data to stay current. This ensures new neighborhoods, shopping centers, streets and other developments that impact routing are accurately reflected on digital maps within the CAD system and MDTs. It is also important that this information can by synced and updated without the CAD system being taken offline. This ensures dispatchers and first responders have consistent access to mission-critical information.

Using Proximity and Area-Based Dispatching in the Same PSAP

Choosing between area-based or proximity dispatching isn't always something dispatchers have to do.

Dispatchers with proximity dispatching capabilities retain the ability to use area-based dispatching. With the two options, CAD operators will often times elect to use proximity dispatching for calls that are life threatening or involve immediate property threats.

Area-based dispatching is then used for other types of calls, such as reports of a burglary that has already happened or incidences that do not involve bodily injury or harm.

Opting to use area-based dispatching even with proximity dispatching capabilities makes it possible for PSAPs covering large jurisdictions to ensure that critical or high-priority calls are always met with the fastest response possible.

When a CFS comes into a PSAP that does not require an immediate response (such as the reporting of a lost item) or is not an emergency, dispatchers with proximity dispatching capabilities can rely upon area-based dispatching to assign an available unit within the CFS' beat or quadrant. Deciding to use one form of dispatching over the other comes when CAD administrators build preconfigured plans for responding to different call types.

When CAD administrators build these plans, fire and EMS units are generally called to service using proximity dispatching. This is because these units are equipped to handle life-threatening needs. In the event of an emergency, dispatchers can always send any unit at any time to a call for service when necessary.

PSAPs that only offer area-based dispatching still offer communities vital emergency services as they use preplans that dictate the best response for the type of emergency call, however, they lack the mission-critical GIS data that proximity dispatching offers.


GIS functionality provides communities with area-based and proximity dispatching capabilities necessary to send emergency responses. With the wide-range of capabilities offered by proximity dispatching, including providing PSAPs with the ability to offer area-based dispatching services as needed, communities experience faster response times driven by GIS data.

Britt Wollenweber is the GIS manager for Tyler Technologies' New World public safety software. He has worked in the GIS field since 1999. Britt enjoys working in an industry that helps save lives and keep communities safe.

Case Study Highlights

  • Robust mapping capabilities in CAD empower dispatchers to send faster responses
  • Embedded Esri functionality in all CAD maps
  • Built-in AVL functionality in New World CAD

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