A new service, just in the nick of time... TECHNOLOGY FINDS MISSING HIKERS THE NEWS-TIMES August 2, 2004 The News-Times/Wendy Carlson When Erica Cywar, left, and Hannah Schiering got lost in the woods, the Danbury Fire Department was able to trace their mobile phone call by using new technology. With a shaky voice, Erica Cywar told 911 dispatchers that she and her friend Hannah Schiering were lost in the woods. The two 17-year-olds were okay, but they had been wandering in the dark for 30 minutes. The terrain was rough, and they were hearing some spooky animal noises. "We shined the flashlight and you could see eyes," said Hannah. In the past, the Danbury Fire Department dispatchers might have sent for a dozen police and firefighters to comb the area for the lost girls. Dispatchers might have called for a state police helicopter. Mobile phone calls were hard to trace. But on July 26, two hours before the girls called, the department had finished installing a system that can locate mobile phone callers. The technology, set to become standard nationwide, is meant to accommodate the growing number of mobile phone users. The technology makes it easier for emergency crews to locate fires or accidents called in from mobile phones. The cost to the state for the mapping software and associated system-wide upgrade is about $4 million. Brookfield, Newtown and New Milford also got the technology in July. Other towns, including, Bethel and Ridgefield will get it in August. The rest of the state goes on-line in September. According to Patrick Sniffin, the Dan- bury Fire Department's communications coordinator, the technology is crucial in Danbury, where the 911 call center received 107 percent more wireless calls in 2003 than it had in 2002. It received 13 percent fewer "wire line" calls. "After that call was over, (dispatcher) Dave Sabel called me and said, 'this new stuff works,'Ÿ" Sniffin said. -------------------------------------------------------------------------------- The girls, Hannah and Erica, both Danbury High School graduates, went for a walk in the Pine Mountain woods near Ridgefield before dark. They wanted to check out a scenic mountain view. But they came down the wrong side of the mountain and became disoriented as the sun set. It was a warm night, but they worried about finding their way home and called 911. "We thought we were coming to a road, but it was a huge pond," said Erica. "I started crying, I was losing it." A home phone shows up at a 911 call center with the number, the name the number is registered to, and the address. Mobile phones typically only display the number and the location of the cell tower the phone is using. "When you used to call from a cell phone, we had no idea where you were. The call went to the state police, who transferred it to us," said Sniffin. "We had structure fires phoned into us and people lost and we had no way of locating them." Hannah's phone used a Ridgefield tower on that call, so it was automatically routed to Ridgefield Fire Department. When the girls said they entered the woods at Olympic Drive, the call was transferred to Danbury. The technology can works two ways. If the phone is newer, it may have a global positioning system chip. Otherwise, the phone uses three cell towers to triangulate and transmit its rough location. The rough location of the phone showed up as a mobile phone icon in an open patch on the map, just less than two miles from any roads. "When we had these kinds of calls, we have put people in the field, sent them out in a search pattern " said Danbury Fire Capt. Steve Williams. Williams, one of the dispatchers on the call, focused on calming the girls. He also used some survivalist tricks to get them oriented. Ridgefield police positioned themselves along Bennett's Farm Road,where they periodically blasted their horns. The girls heard the horns faintly, and they walked towards them. When the girls stumbled onto a trail, everyone was relieved. Ridgefield police took to one of the trails in hopes that they would find the girls. They began to call to each other. "I felt better when we saw the trail," said Erica. Soon, the girls spotted police on a parallel trail. Officers had them call their parents, and shuttled them home. Roughly an hour after their 911 call, they were safe and sound. The girls said that they were pleased that dispatchers hadn't called in helicopters or search dogs. They were embarrassed enough. "This makes me feel comfortable that they have this thing that can help find you when there are no houses around for miles," Erica said. When a mobile call comes in, dispatchers will get an indication of where the caller is within a radius of as much as several hundred feet. The system allows them to send a signal to the phone to home in, and get a better sense of where the caller is. Police can not trace a cell phone's position if its battery dies or if it is turned off. In the end, Erica said she got a better feeling about police. "I always felt like they were out to get me, you know, give you a speeding ticket," she said. "This felt like they were there to help."
This is great that the girls were able to be found with GPS from the phone. Its even better that there was coverage in the middle of a forest. Now for the location technology that uses multiple towers to locate the phone, would it have not worked this time? The chances of connecting to 3 towers at once in a forest isnt that great.
Actually the article did not state which technology was used in this case. I will check, but I think, Network option, not GPS was used here, at least that is my inside information...both systems are used in CT From the CT state: "Connecticut will be one of the first states to have the capacity to locate a person using a cell phone who makes an E 911 call, according to George Pohorlak, director of the Office of Statewide Emergency Telecommunications. The locating system is largely in place now and should be in place statewide by the end of summer. According to Pohorlak, five of the six major cell phone companies serving the state have already deployed their systems. Nextel, Sprint, and Verizon have deployed the GPS option, while AT&T and Cingular have deployed the network option. T-Mobile originally chose the GPS option, but has decided to use the network option instead. Pohorlak anticipates that T-Mobile will complete the deployment of its system by this August. His office will test the accuracy of the systems. Twenty of the state’s 107 PSAPs have electronic maps that automatically display the location of a call using the information provided by cell phone companies. Pohorlak anticipates the remaining PSAPs will have this capacity by the end of June."
In the 911 field this is called Wireless Phase II technology. All cell phone carriers are required to have this feature on new phones. Each state has it's own required date. This will not work with older phones. Over 40 percent of 911 calls in NJ come from cell phones.
Right you are... more info for the curious: In 2001, the Federal Communications Commission (FCC) required cell phone companies to develop the capacity of automatically locating callers. The mandate has two phases. In the first phase, the companies were required to develop systems to identify the location of a caller based on the cell phone tower or antenna that first picked up the call. This allowed companies to locate the caller within an area that ranged from a few blocks in cities to one-mile circles in rural areas. In the second phase, cell phone companies have two options for significantly improving the locating capacity. They can install GPS chips in their telephones. The chip determines the phone’s location (in hours, minutes, and seconds of longitude and latitude) by receiving signals beamed down from an array of satellites. The chip determines the location based on different arrival times of these signals. Alternatively, a cell phone company can comply with the mandate by using information provided by its network. This approach uses towers and antennae in the carrier's network to measure the timing of signals emitted from the phone, and thus its location, Under the FCC mandate, by the end of 2005, companies using the GPS approach must be able to place 95% of calls they handle within 150 meters (approximately 500 feet) of the actual location, and 67% of calls within 50 meters (approximately 165 feet). Companies that use the network option must be able to place 95% of calls within 300 meters and 67% within 100 meters. Further information about the mandate is available at http: //www. fcc. gov/911/enhanced/.
From the sounds of it, the phone was probably using CDMA since GSM does not have GPS locator services as a standard option, at least this is the case in Europe. Furthermore, CDMA is a bit ahead of GSM in this area, Nokia's US CDMA models all list GPS as a standard feature whereas the GSM models do not. Great to see a happy ending here.
Actually it is not clear at all from the article. A call into the local fire department didn't resolve the issue either. The dispatcher's gut feeling was that it was a GPS phone, but he stated that both Verizon and Cingular have great speed and accuracy from his tests. Verizon is GPS; Cingular is triangulation. He didn't have the logs available (for that night) to determine which carrier it came on.
Don't forget about something called "triangulation" that GSM uses. It uses GPS technology, but it is located in the towers. Therefore, GSM phones don't need GPS. The GPS receiver is just one more thing that shortens battery life, so it is good it is not on GSM phones and on the towers instead.
Great thanks for the clarification on that part, bobolito. It definitely makes sense since a cell tower doesn't run primarily on battery power .
I really know very little about GPS used in cell phones, but know more about plain personal GPS units. I wondered how a pure cell/GPS would be in buildings or in dense woods...normally they have a difficult time (speed wise) or don't work at all. Below is some info that WA user XIKLE found on phonescoop and posted june 2004: GPS (Global Positioning System) is a global satellite-based system for determining precise physical location. Most phones with "GPS" in fact use A-GPS technology. The "A" stands for assisted, and means that the phone relies the network for help in determining location. Although the phone does receive GPS signals directly from the satellites, it can't determine actual location without help from the cell network. A-GPS (Assisted GPS) A type of handset-based position location technology. To determine location, the phone takes readings from both GPS satellites and nearby cellular base stations (towers), with the help of a location server on the network. The location server on the network is required to tell the phone which satellites to look for, and also to perform the complex calculations that provide precise location information. This technology generally provides better accuracy than GPS-only and network-based technologies. A-GPS also works in places where GPS-only technologies do not work well, such as dense urban areas, inside buildings, and in moving cars. So is it true that GPS phones also use triangulation, with GPS for more precision? And inside buildings or home where GPS does not work, relies only on a network, triangulation system (such as Cingular uses)? It sounds like it works always as a mixed system (and hence impact on battery life). Any help from the more knowledgeable is appreciated. :wink:
Everybody is in the woods in northwest CT, so getting 3 towers probably would not have been unusual. :biggrin: But with even one tower, the time signal flight would have given a circle of known radius from the tower. Since these girls knew what forest they entered, that would have elminated the need to look around a full 360 degrees from the tower. Two towers would have given excellent precision; with three towers, the girls wouldn't need to know what forest they were in. The same logic would apply if one were on a known highway, but didn't know the exact mile marker. With one tower, the highway is either on one side or the other of it. Unless you were stuck on a rotary and the cell tower was in the center of it :wink:
The good thing is towers are most of the times divided in 3 sectors. So, depending on which sector your phone is using, the network can determine what direction from the tower you are in. Using both methods is always the best technique, but it really depends on the network operator if they support network assisted GPS. So even if the phone has GPS on its own, the network operator may not offer network assisted GPS. It is always good to have network assisted GPS because many people still have old phones that don't have GPS receivers and many new ones don't have it, not to mention that handset GPS doesn't always work if you are under something like inside cars, buildings, etc.. Network assisted GPS is more reliable in that sense because it is always available and doesn't stop working when you go under some roof or tree or something is blocking the sky such as a building. Towers are always outside and free to "view" the sky so they never get blocked from the GPS satellites.
Bobolito: This is a good point...you mean that the 3 sector array layout of a tower give some direction information even when only one tower is available? I assumed this might be the case, if I understood towers correctly. That is good news. I'm not sure how you use the phase 'network assisted GPS', perhaps in two ways? Do you mean a GPS unit in the cell with network assistance or a network location service that give GPS-like coordinates, but without a GPS chip in the phone headset (meaning the GPS is at the towers instead)? i.e. A-GPS versus Network Solution In anycase we agree that a network based location service has more reliability, with or without the GPS handset chip.
Well, 19 cents very well spent I think. From a CT paper in July: ...figuring out where wireless emergency calls are coming from became much easier for the town’s police department Tuesday, when the department received free cellular phone tracking equipment through the Connecticut Department of Public Safety. With the new equipment, dispatchers will be able to pinpoint the location of many cellular phone calls within 100 to 150 meters by using a computerized map of the town, said Larry Cole, associate director of public safety for SBC Corporation, which provides equipment and service for all 111 Connecticut 911 dispatch centers. However, only AT&T and Cingular brand cell phones are fully compatible with the tracing system, Cole said. The system will also work with newer models of cellular phone brands that contain Global Position System computer chips, but dispatchers will only be given very general location information about older phones without the chips, he said. Financing for all 911 equipment upgrades comes from the state’s "E-911" fund, which derives from surcharges applied to every cellular or land based phone line in the state, according to Wayne Maheu, executive director for the Department of Public Safety’s division of fire, emergency and building services. The surcharge is formulated yearly upon the needs of the state’s 911 systems, and is presently 19 cents a month, he said.
Yes, the tower sector gives directional information. That's how triangulation is calculated. Other towers assist by using their particular sectors as well and information about signal strength from each sector helps too. Now, don't forget that as you go indoors, reception always deteriorates so that may throw off the calculations done by triangulation. In other words, because reception decreases while in a basement, the tower may think that you are more far away from the tower than you really are. Network assisted GPS is a GPS system installed in the towers. In some towers, besides the panels you can always see a small thin antenna with a rounded head. This is a GPS antenna. It will always know its own location because towers don't move, but to locate a cell subscriber it will use signal strength information from the cell to the other towers (if any) and which sector of the tower is picking up the signal. This is triangulation or network assisted GPS. This coordinates information can then be forwarded to emergency services to locate the caller. If the phone has its own GPS chip, then the network provided information can then be combined with the phone's own GPS receiver coordinates for greater accuracy.
I wouldn't think that the error in the time of a signal to go from a tower to my phone and back would be great, even in my house. But it really doesn't matter too much...my house is much less than 300 to 600 feet in any direction! :wink: The best error with a e911 location system is still bigger than my house.
It's not really a timing issue. It is that distance is calculated based on signal strength from the different sectors. So if you go indoors and you shave off 10dbm off your reception the cell may think you are further away from it. However, since triangulation is direction-based, the other towers negate this effect, but still it creates a larger error than if you were outdoors because in most cases your phone will pick up less towers when you are indoors as the signal from the weaker towers dissapears.
A little bit of googling today. Seems that a lot of systems have been out there over the years (global positioning system (GPS), Assisted GPS (A-GPS), Time Difference of Arrival (TDOA), Enhanced Observed Time Difference (E-OTD), Advanced Forward Link Trilateration (AFLT), EFLT, Radio Fingerprinting, angle-of-arrival (AOA), mobileassisted network location (MNLS), Cell ID, Enhanced Cell ID and Enhanced Cell ID with Timing Advance). But the one's now employed (since most of the above had problems) are A-GPS and U-TDOA (Uplink Time Difference of Arrival). A-GPS for CDMA and U-TDOA for GSM. Cingular and all the other GSM carriers use U-TDOA. Europe is in on the standard too now. This is based on timing signals . Measuring signal strength would mean placing the phone in my pocket and my position is off: not as fool proof as a system based on timing(pretty much the way GPS works with sattelites). see: August 2004 article Also, see: Cingular signs UTDOA deal for GSM networks.
Well if they were able to find them with E911 and had coverage it was most likely CDMA, since the built in GPS is so much more accurate and dependable.
yep... yep... yep... of course, as long as you don't go under some roof or something that blocks the view of the sky, it is always reliable.
Oh boy. After a few days of googling, talking with the E911 dispatcher in the above case, my own experience with GPS handheld, and time of flight measurements I concluded that there is no strong reason to worry about having CDMA or GSM (or TDMA,AMPS) for E911 service. Thanks to the FCC mandate, you will be found with similiar speed and accuracy. Unlike the EU, the US government made a mandate with teeth and fines. Many ideas had some quirks. I came across a story about a guy with a GPS chip and was asked by the E911 dispatcher to move closer to his window (and hold the phone out the window) so they the GPS would work better. Hence, A-GPS and not pure GPS. But true, given enough time (maybe 10 minutes) a better location could be given. On the network solution, having only 1 tower will cause some ambiguity (as mentioned above in this thread), but it is not a disaster. But the network U-TDOA solution works well in buildings (or heavy forests) and works with all phones now and with all formats (CDMA,AMP,TDMA, GSM). The E911 dispatcher confirmed to me that both Verizon and Cingular had great speed and accuracy for the job based on their usage. In the 911 case above, the location of the girls was displayed as an icon on the map, showing them near the pond. But the police didn't really go to them, but lined the cars up on the nearest road and honked the horns. The girls and police walked toward each other based on the horn sounds. The old fashioned way in the end. So I read that both systems are dependable and accurate enough at present, and have to be, because the FCC mandated the test conditions. Hats off to our government for forcing the providers to do something, and fining them when they didn't. Now the providers are realizing that they have a potential revenue stream as add ons; where my kid, my cheating spouse, where am I, how close am I to that ATM machine? The reason, I learned, that Europe (and by implication GSM there) is behind the USA rests on the fact that the EU only suggested that something be done, but provided no guidlines or penalties for doing nothing. It is not a CDMA or GSM thing at all.
A voice of reason has just been heard. Thanks for the info Viewfly. We all learn something new in these forums.
