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FINDING MISSING PEOPLE BY LOCATING KEYS- NEED HELP BUILDING PROTOTYPE

KALIMOUSE

New Member
I have been apart of 100's of search and rescue operations and the highest common denominator are some missing people have transponder keys in thier possession. . Since 1995 most cars keys have transponder chips inside of them.

A few months back, I started to research different methods on how to enhance our searches on new and old cases. If we are able to search for transponder keys, this would narrow down our search areas drastically and could save alot of lives.

I need help to create a long range transponder key detector that could be attached to a drone. I found a few manufactures that sell detectors but I don't have experience on how to amplify the signal.
 

Diver300

Well-Known Member
Most Helpful Member
I don't think that it's a practical idea.

The transponders that became common after 1995 are RFID devices, with a range of a few centimeters. There is no battery in the key's transponder. The transponder is powered by a coil in the car, and the same coil picks up the code from the transponder. The technology is similar to that used for contactless credit cards or for the microchips implanted in pets, so the range is similar.

The radio transmitters that are also part of those keys are only activated when the button is pressed. There is no electrical connection between the the radio transmitter and the transponder.

Cars with keyless entry use a low frequency (125 kHz) signal from the car to activate the radio transmitter at 300 - 450 MHz in the key. It's possible to activate those from several metres away. However, the keys may only respond if the correct signal from the car is received, to get a good battery life for the keys by stopping them activating if someone tries to unlock a different car nearby. Also some car keys will not respond if they have not been moved recently. That is to prevent theft where the range extenders are used to relay the car's signal so that it appears to the key that it is close to the car when it's not.

Of course, the devices used by thieves to activate the keys from several metres away don't have the power or weight constraints that a detector on a drone would have. The car's 125 kHz transmitter can afford to use quite a lot of power, because it is only activated when someone tries to open a door. A drone that is searching would need to transmit all the time.

So I think that only some keys would work. It would only be ones for keyless entry cars, excluding any that won't unlock unless moved. You may need to copy the code the car transmits in order to get the key to respond. The range would be a few metres at best, and power and weight of the transmitter needed would be a problem.

I know that it was a rather different application, but detonating magnetic mines from an aircraft needed large coils and a lot of power:-https://www.historynet.com/aerial-minesweeping.htm
 

tomizett

Active Member
There was a long thread on here a while ago on a similar topic, by someone who'd lost their keys somewhere down a long track. Might be worth a search for that?
 

Pommie

Well-Known Member
Most Helpful Member
Ping their phone.
If you could make a mobile cell phone tower on a drone then triangulating their position may be a possibility. It wouldn't need to be a full access tower, maybe just an emergency only tower. Just a thought.

Mike.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If you could make a mobile cell phone tower on a drone then triangulating their position may be a possibility. It wouldn't need to be a full access tower, maybe just an emergency only tower. Just a thought.
Triangulation, by definition, needs three receivers to locate it with any accuracy - the location using cell towers in crime programmes is wildly exaggerated, they can only guess based on the relative signal strengths from three towers (assuming three towers can hear the phone?). Obviously this is MUCH better than nothing, but you're probably looking at miles not yards.

Even worse, the kind of places you're likely to need rescuing from are often the very places with absolutely zero cell coverage - I often used to walk in areas where you had no signal at all, no good trying to use on-line maps on your phone :D
 

rjenkinsgb

Well-Known Member
Most Helpful Member
the location using cell towers in crime programmes is wildly exaggerated, they can only guess based on the relative signal strengths from three towers (assuming three towers can hear the phone?).
The FCC mandated handset positioning capabilities for emergency services, starting over 20 years ago.
It started at 50 metres target and 300m worst case back in 2001 and the latest specifications released last year aim for three metres accuracy including altitude.

If I'm understanding the text, the 3m horizontal positioning requirement came in last year and the vertical accuracy requirement comes in next year (presumably for new equipment).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
And a drone can move around!!! Maybe even to three different locations!!!

Mike.
But you want a direction, not a crude signal strength.

I presume lack of cell towers is a much more serious problem in Australia?, but it's bad enough here in the locations you're likely to get lost or injured.

Kinder Scout is the highest point in Derbyshire, the start of the Pennine Way (which goes all the way to Scotland), and is a call phone dead spot.

I was walking up there the other year, nice bright sunny day, and I got this strange 'tingling' feeling, like someone was watching me - looked all round, nothing but heather, peat bog, and desolation - then I looked up. Just above me (looked like I could throw stones at it) was an air liner - quietly floating along, presumably on the flight path down to Manchester airport, which isn't far away. It was really spooky :D
 

Nigel Goodwin

Super Moderator
Most Helpful Member
The FCC mandated handset positioning capabilities for emergency services, starting over 20 years ago.
It started at 50 metres target and 300m worst case back in 2001 and the latest specifications released last year aim for three metres accuracy including altitude.

If I'm understanding the text, the 3m horizontal positioning requirement came in last year and the vertical accuracy requirement comes in next year (presumably for new equipment).
Presumably this is using the phones in-built GPS, and asking it where it is?. And of course the FCC has nothing to do with the UK, or anywhere other than the USA.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Presumably this is using the phones in-built GPS, and asking it where it is?. And of course the FCC has nothing to do with the UK, or anywhere other than the USA.
The point I'm trying to make is that it's a capability required in the equipment so something manufacturers must create and include, and it has been in use to some level for a very long time.

UK law may take a while to catch up, but it has also been required here for some years. Any in use elsewhere in the world is obviously "feasible", so also required here.

Part of the OFCOM conditions of service for mobile operators:

4.2 The Communications Provider shall, to the extent technically feasible,
make accurate and reliable Caller Location Information available for all
calls to the emergency call numbers “112” and “999”, at no charge to
the Emergency Organisations handling those calls, at the time the call
is answered by those organisations.


Remember that the GSM system inherently needs to calculate the path length to each device, so the time division multiplex replies can be properly interleaved and not overlap other timeslots.

The GSM system only uses increments of around 550 metres on air, but there is no reason the actual timing system cannot be far more precise and give path length down to a few metres. It still needs two or more towers to get a location better than a radius, though.

Re. the accuracy of locating mobile phones in film and TV, where they have to keep a call active for minutes, to pin down a location - the great lie is that any government agency would not usually have the precise location instantly!
 

ronsimpson

Well-Known Member
Most Helpful Member
Ping their phone.
If you could make a mobile cell phone tower on a drone then triangulating their position
All the recent phones I know of report their GPS position. Even when that function is turned off. I lost my 4 year old phone and the battery ran down. The phone company reported to me where it was then the battery ran down. Using another phone I walked to that spot in the field. If the lost person was outside cell range, the phone company knows where the phone was when it went off grid. (direction, speed, location)

They also know the temperature of the phone. Signal strength, battery usage, (probably how much port you watch). lol
To my relatives that are not getting vaccinated because they don't want "chipped" and don't want the government & Bill Gates knowing what they do; it is too late. Your phone knows all.
 
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Pommie

Well-Known Member
Most Helpful Member
All the recent phones I know of report their GPS position.
So, if a drone can become a temporary mast in the sky and make any contact it would have their (or the phones) position.
Here in Australia, there is very weak coverage in more remote areas that will only handle emergency calls (no matter which network). Is this a global thing?
To my relatives that are not getting vaccinated because .......
Too true, carrying a phone tells them everything they need to know. Many times, I've had conversations about the most obscure things whilst my phone was in my pocket. By some really strange coincidence, I started getting adverts for those really obscure things!!!

Mike.
 

Visitor

Well-Known Member
It's very hard to "drop off the grid" these days. Your phone provides all kind of info on your whereabouts, but even if leave it at home, your leave a lot of other crumbs in your path:

□ Pay with a credit card or use a debit machine

□ Use a club card or a rewards card at a store

□ Drive on a road or cross a bridge with electronic tolling.

□ Drive on a road with remote traffic monitoring
 

ronsimpson

Well-Known Member
Most Helpful Member
that will only handle emergency calls
Can not speak for all countries..... In the US all phones (even old unused phones with out a plan) will call 911. (HELP number)
So, if a drone can become a temporary mast in the sky and make any contact
I think a real problem is that most people power down the phone when out of range. (drone is a good idea)
 

gophert

Well-Known Member
Most Helpful Member
To my relatives that are not getting vaccinated because they don't want "chipped" and don't want the government & Bill Gates knowing what they do; it is too late. Your phone knows all.
and the same people are checking or posting their deepest political and religious opinions on Facebook every 15-minutes (or more frequently). A Facebook data scraper would be better than an injected microchip from Bill Gates.
 

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