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Tips for calling 911 with a cell phone - A peek under the hood

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I am a software developer working with online maps and location technology. Earlier this 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 happens behind the scenes?

Much of what I learned came from reviewing documents on the FCC’s website. 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 many 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 (or handheld GPS) is often 10 times more accurate - or more - than the coordinates produced by the wireless carrier handling a 911 call.

Recently I finished a report that shares what I learned. 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.

I posted a copy of this report on my server at

Here are the tips. I am happy to answer questions.

--- Tip #1 ---
If you need to call 911 and your cell phone shows ‘no service’, then you should call 911 anyway and let it ring 45-60 seconds before hanging up.

--- Tip #2 ---
You should give the 911 dispatcher your location by providing (1) a street address, or (2) a verbal description the dispatcher understands, or (3) your latitude longitude coordinates expressed as decimal degrees.

--- Tip #3 ---
FindMeSAR is a browser app that was developed as a public service specifically to provide an easy and ‘no cost’ way for anyone with a smartphone to display their coordinates and accuracy value while their phone is either online or offline. This is not a commercial product of any kind. It is a volunteer project just to try and help people when they need help.

--- Tip #4 ---
When you call 911 with a cell phone the wireless carrier handling the call might not produce *any* coordinates for your location.

--- Tip #5 ---
Even if the wireless carrier handling your 911 call does produce coordinates for your location, the coordinates you can obtain from your smartphone are either (1) more accurate or (2) a lot more accurate than the coordinates produced by the wireless carrier.

--- Tip #6 ---
If (1) your phone is not within range of a cell tower and (2) your phone does not have a current copy of the satellite ‘assistance’ data, then it will take 15 to 20 minutes before your phone will produce coordinates for your location.

--- Tip #7 ---
No one is monitoring the wireless carriers to see whether or not they are in compliance with the standards and requirements that the FCC has adopted regarding wireless calls to 911 and coordinate data for the caller’s location.

--- Tip #8 ---
If you have an android phone then to get the most accurate coordinates set the location mode (or method) to “GPS only”.

--- Tip #9 ---
If you have an Android phone then there is a free and easy way to find out if your phone can produce more accurate coordinates by using data from both the USA satellites (GPS) and the Russian satellites (GLONASS).

--- Tip #10 ---
Phones that have no service plan at all can still (1) call 911 and (2) run an app that displays coordinates and accuracy on the phone’s screen.

--- Tip #11 ---
If at all possible, make a voice call to 911 instead of texting.

--- Tip #12 ---
If you do text to 911, then the dispatcher is most likely not going to have *any* location data for you unless you include it in your text.

--- Tip #13 ---
After you contact 911 take steps to make your phone’s battery last as long as possible.


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I called 911 for the first time ever last June when the screaming in the room next door at a motel escalated to life threatening verbage!

I could not believe the questions I was asked by the operator!

Actually thought I was the one in trouble by the time I was finished!

Interesting information!!!

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Great topic. Thanks for the hints.


Can 911 get texts anywhere? Or only in certain cities?

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Can 911 get texts anywhere? Or only in certain cities?


Only certain 911 call centers can receive texts. So far, most call centers cannot do so. To find out, I suggest checking with your county sheriff's website.

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The single biggest reason why wireless carriers cannot routinely provide accurate coordinates to 911 call centers is because the FCC prohibits the carriers from getting the user's coordinates directly from the user's phone.


See p.4 of the report I produced and the discussion of GLONASS. The link to the report is at the start of this thread.

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I have called 911 from a cell and a freeway and was connected first to a city agency center then transfered to DPS center. I had to give directions of my current location as well as the go forward location. Had DPS call my cell back to ask me for location updates and action in this case of a car/ driver.


I added the SAR browser to my home screen, thanks.

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Here is a followup idea to help find people that have called 911 and are not able to give a street address or adequately describe their location.

As explained in the report I posted, when someone with a cell phone calls 911 the wireless carrier is supposed to make reasonably good coordinates available to the dispatcher. Often times that system works fine. But also many times this system does not work well and either the wireless carrier never produces “phase 2” coordinates or do so but the accuracy of the coordinates is terrible.

There are 6,000+ 911 call centers in the USA. These are known as PSAPs (Public Safety Answering Point. The problem of wireless carriers not providing accurate coordinates for wireless callers is going to vary from one PSAP to the next.

Now here is the idea. When a 911 dispatcher has a problem getting an accurate location for a wireless caller, the dispatcher can ask the caller to:
1. Browse to findmesar.com
2. Tap the "Next format" button until the yellow screen appears. This screen shows the caller's location in decimal degrees which is the same format the wireless carriers use to send location data to 911 call centers.
3. Wait a few seconds for the accuracy to get to 30 meters or smaller.
4. Tap "Stop"
5. Read off the coordinates, accuracy, timestamp and (optionally) elevation.

No, this will not work in every case. FindMeSAR does not work on flip phones. And the first time someone tries to use this app their browser has to be online. Unless the phone is on wi-fi, this means the phone has to have a data plan.

Yes, FindMeSAR will work in many cases and the person who called 911 for help will be able to very quickly read accurate coordinates to the dispatcher. Here is a short report from a SAR team in New Mexico that used FindMeSAR to locate lost hikers. The story seems to indicate that “phase 2” coordinates from the wireless carrier were also available but they were not accurate. http://atalayasar.org/

Also FindMeSAR has been reviewed and added to the APCO app page at APCO is an international organization for public safety communication professionals.

If you know someone who works in public safety (dispatcher, police, fire fighter, SAR, etc) please consider asking them to take a look at this idea of your local PSAP using FindMeSAR as a backup plan to help locate wireless callers.

Finally, I will point out again that FindMeSAR is not any kind of commercial product. Over the years I have traveled in the backcountry a fair bit on foot, skis and horseback. Fortunately I have never needed to call for help but I know people that have not been as lucky. This volunteer project is part of my way to 'pay it forward' and also show appreciation for all those involved in SAR and other emergency response.


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