Cannon County 911 Works To Improve GPS Mapping
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Most anyone that travels today has some type of GPS device and is also used commonly by emergency response personal.

The Cannon County 911 Emergency Communications District, in a joint venture with various GPS device manufactures like TomTom as well as IP based mapping serves such as MapQuest are teaming up to correct map errors on the services they provide to the public on commercial devices and internet mapping services.

As more and more people purchase their own GPS devices, the discovery of mapping errors is becoming more prevalent.
Cannon County 911 does monthly GIS (Geographic Information Services) updates on our mapping servers so that 911 calls are mapped correctly when a 911 call comes in. Any errors that are discovered are quickly corrected and updated on our servers.  Unfortunately there has been no way of communicating this complex data with the private sector in such a way that is sufficient for all the agencies involved.
GIS mapping consists of numerous map layers that are displayed simultaneously on the dispatchers computer screen. Map layers and fields that currently display on a dispatchers screen to make it work are Street Center Lines, Address Points, ESN Lines, Pre Directionals, and Post Directional fields to name just a few.

This information is required in order for the information in the MSAG Data base (Master Street Address Guide) to be able to communicate with 911 Data Base when a 911 call comes in . Some of this same information is included with the telephone company account information and is embedded in the caller’s phone number called ANI (Automatic Number Identification).

When the call comes in, the ANI is matched with the MSAG data and is automatically displayed on the dispatchers screen referred to as ALI (Automatic Location Information).  This results in the caller’s information and location being displayed automatically so the dispatcher can focus on helping the caller and getting the appropriate emergency agencies en-route thus reducing dispatch time. Another layer on the dispatcher screen is an ortho layer which displays the GIS data over a Satellite image of all of Cannon County.   

With the rapidly increasing number of cell phones in use today, the use of GPS satellites has also greatly increased. There are 24 NavStar Satellites in orbit that broadcast position and time information to the GPS units back on earth. Modern cell phones utilize this GPS information as well as the common name brand devices such as TomTom and Magellan.

Cannon County 911 initially began trying to improve the numerous GPS map errors by physically visiting the map error site and manually inputting the corrected data into a GPS device and up loading to the GPS provider’s network servers. This has been time consuming, not very efficient and is vendor specific.

The Cannon County 911 Emergency Communications District has been working with the TECB (Tennessee Emergency Communication Board) in the implementation of NG911 (Next Generation 911). When fully completed, 911 services in the State of Tennessee will be completely IP (Internet Protocol) based, and will be on a statewide network.

Currently 911 calls are routed via expensive, dedicated trunk lines that run to the 911 center. After NG911 is operational, these trunk lines will go away and the resulting state network will be much more redundant and will result in multiple 911 districts sharing a 911 controller. This will reduce cost and greatly reduce the chance of any 911 call not being routed to a 911 call center, regardless of the amount of calls that come in simultaneously.

Currently trunk lines have only one route into a call center and if there is any failure in the route, the call cannot be routed correctly. NG911 will result in multiple pathways and will be automatically rerouted in the event of a failure, whether it is manmade or natural. NG911 equipment installation for Cannon County will begin in the early part of 2012 with a completion date sometime in 2013.

Part of the NG911 process is completing a state wide standard for GIS mapping called TIPS (Tennessee Information for Public Safety). TIPS is a comprehensive dataset that contains various GIS data layers benefiting public safety agencies within state and local government. This will enable all GIS data to be on a state wide standard and make the data sharing process much more effective. This will enable the transfer of all the information of a 911 call including the map data from one county to another.

When a cell phone caller dials 911, it will hit the closest cell phone tower which may be in an adjoining county and has to be transferred to the originating county. Currently when a call is transferred, only the voice can be transferred and not any of the information associated with the call.

The NG911 process has been instrumental in the formation of new partnerships to share data and make it more available instead of being proprietary to a single agency or district. The data shared with the commercial vendors is not edited in any way and is used only as a reference layer to validate the commercial vender’s data. The ortho satellite data will not be submitted and the vendor will continue to use their own ortho imagery such as Google Earth or Google Maps.

Unfortunately the process in correcting map errors at the public level is not going to happen quickly. Most commercial vendors agree that the validation process will take from three to twelve months to complete once they receive the data. It will also be dependent on people making sure they update their devices. Not all devices will automatically update and have to be done manually.   

Any questions or concerns with mapping errors, you can contact 911 Director Roy Sullivan at 615-563-4322, email at or on Face Book at Cannon Dispatch.

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