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Tips for calling 911 with a cell phone

Posted: Sat Sep 02, 2017 5:09 pm
by Jelff
I am a software developer in the field of online maps and fairly new to this forum. Any maps or other work that I post about here at storm2k are a public service and part of my way to “pay it forward”. They are not part of any commercial endeavor.

Last year I became interested in what happens when someone with a cell phone calls 911. In particular I wanted to know the details of how the 911 dispatcher learns the *location* of the caller. What kind of digital magic was happening behind the scenes?

On one hand I learned that the FCC requires a wireless carrier handling a 911 call to produce coordinates for the caller’s location. Sounds good, right? On the other hand I learned that some carriers have exempted themselves from this requirement over large portions of the area they serve. I also learned that the coordinate accuracy most of us easily get on our smartphones is often 10 times more accurate - or more - than the coordinates produced by the wireless carrier handling a 911 call.

Keep in mind that there are over 6,000 911 call centers. Problems related to getting an accurate location for wireless callers will vary among all those call centers. Some call centers will rarely have a problem getting an accurate location for wireless callers while at other call centers this problem will occur more frequently

I boiled down what I learned and put it into an easy-to-read report which I am hosting on my server as a pdf file. That report consists of:
1. A list of tips for calling 911 with a cell phone.
2. Background information so you understand the big picture.
3. Detailed information to support each tip.
For those wishing to dig into the source material for themselves, the report includes links to various documents on the FCC website.

Report: ... -phone.pdf

Early on as I dug into this topic it became apparent to me that everyone needs an app on their smartphone that will (1) be easy to use in an emergency, (2) minimize any possibility of user error, (3) display their coordinates in the proper format and (4) will also display the equally important accuracy value for those coordinates.

That realization led me to develop FindMeSAR ( You *do not* get this app from an app store. Instead, FindMeSAR is a browser app and all you need to do is open the link in your browser. When you open the app for the first time you will see a blue screen. Tap the “Next Format” button until you see a yellow screen. The yellow screen displays your location in latitude longitude decimal degrees. Every 911 call center in the country uses that coordinate format.

The app includes a “Tips” button and an icon you can save on your screen.

To read more about FindMeSAR please open the pdf file I posted above and go to page 6.

No doubt some people who read this post already have an app on their phone that displays their coordinates and the accuracy value for those coordinates. Great! But what about your spouse, children, relatives, friends, and co-workers. Do they know the importance of having an app on their phone that meets the criteria I described and do they have such an app?

Now let’s bubble up. Here is what I would really like to see.

When someone calls 911 with a cell phone and (1) the wireless carrier does not provide coordinates with good accuracy and (2) the caller cannot adequately describe their location, then the call-taker should ask the caller to:
1. Browse to
2. Tap the "Next format" button until the yellow screen appears.
3. Wait a few seconds for the accuracy to get to 30 meters or smaller.
4. Tap "Stop"
5. Read off the coordinates and accuracy.
6. Turn location services off to conserve their battery.