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RolfGutmann
(@rolfgutmann)
Community Legend

In a murder case we had to find an iPhone 5s which was thrown to avoid collection into a river. At the time of throwing the iPhone was switched on and Find My iPhone (FMi) activated. The river had a low level of water depth about 1m but bad optical contrast as black case and river ground almost dark.

By calling the iPhone it responded by being reacheable and functional to ring. This proves that cell tower reception was duplex running. FMi is based on cell towers, WiFis and GPS - all just as available at the time. So accuracy of location of FMi is in worst case 10-20 square meters wrong. Our divers got the device successfully, but

How could the weak signal (paging) of the iPhone underwater be detected without divers?

We try to build a swimming construct with own GPS and RC-controlled strong lamps and vertical underwater-cam with real-time video transmission to land. What we are unsure is how to design and build a sensor head to locate the signalling of the iPhone. The process to find the device is very time-sensitive as battery will run out and may water damage will make the device non-responsive.

Have you a solution running for this in your corps? Any other good idea?

We want to learn from the Best - You!

Thank you.

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Posted : 13/01/2017 6:04 am
droopy
(@droopy)
Active Member

If you are running a goverment or justice research, use trilateration of Mobile cells which gives you a very precise location similar to GPS (10 meters aprox).

Depending on which country are you located, i could provide you location by phone number using trilateration on SS7 worldwide. (only for goverments and if country is under coverage)

Any underwater RF finder will do the trick as you could see the connection to tower.

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Posted : 13/01/2017 5:26 pm
RolfGutmann
(@rolfgutmann)
Community Legend

Thank you droopy for your offer.

I am in action for Law Enforcement, Gov.

To locate a cell phone by SS7 I was aware, but how does this fit into the core network in-country running on Diameter and Attribute Value Pairs AVPs? As a cell phone can be connected by Mobile Broadband Network, WiFi or DSL (WiFi interworking) or even DSL-LTE Bonding where does the SS7 reachability actually ends?

As small and macro cells evolve with operator's public WiFi Access Points AP a solution based on IP could be the most accurate solution to come close to the location and the Tracking Area Code TAC (LTE) or Location Area code LAC (UMTS)?

As you are an expert please help me to better understand the solution after 'AnyTime Interrogation ATI'.

Please help me.

Update We test underwater RF Signal propagation in that river to replay the situation a few days ago.

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Posted : 13/01/2017 6:33 pm
droopy
(@droopy)
Active Member

You could use VLR location to interrogate a mobile.
SS7 has this feature carrier to carrier under agreements.
We have access as goverment to it for location. Depends on which country and carrier you have.

We use trilateration and have less than 10 meters accuracy which is same or better than GPS.
It is mainly use for terrorist tracking but it could be use under an official request.

Even you could trace back from Apple servers the findmyiphone previous locations tracks and historical data for many weeks or years. But legal authorization is required.

Techinically, you could always locate a mobile in the world.

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Posted : 13/01/2017 11:10 pm
C.R.S.
(@c-r-s)
Active Member

Update We test underwater RF Signal propagation in that river to replay the situation a few days ago.

The propagation loss for a 800 MHz signal in 1 m freshwater is around 30 db, and around 70 db at 1700 MHz. It's not worth the effort, I think. However, it could be an advantage and lead to some results when using active GSM equipment, that the handset is probably pushed to GSM just by the environmental RF shielding (at least if registered for a low-band network).

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Posted : 14/01/2017 4:56 am
trewmte
(@trewmte)
Community Legend

Rolf, are these any help to you

Electromagnetic Wave Propagation into Fresh Water
http//file.scirp.org/pdf/JEMAA20110700001_18390291.pdf

RF Path and Absorption Loss Estimation for Underwater Wireless Sensor Networks in
Different Water Environments
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4934316/pdf/sensors-16-00890.pdf

ReplyQuote
Posted : 14/01/2017 8:59 am
RolfGutmann
(@rolfgutmann)
Community Legend

@droopy, first thank you! After Carsten Nohl (srlabs) revealed the SS7 attack many operators closed the ATI command. Focussing on the VLR is a good approach. #Find My iPhone location request in certain cases is too slow and I fear to get no more RF signal from the device. But will test.

@C.R.S. Thank you for RF signal path attenuation values, deducted from av. values of -70 - -100 dBm I guess at about 2 meters the end comes for the overwater approach. Dropping 3 sensors to measure unterwater requires a fine-tuned upriver approach to get close to the device (to avoid durt swirling up). This ground-based approach seems impossible, but never give up. To drop e.g. M-TMSI-catching (LTE) sensors would push the device to power-up his RF signal. But the serial/sequential round-robin approach 1-2-3 has to be timely delayed between to not confuse the device. Seems costly.

@trewmte Thank you!

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Posted : 16/01/2017 11:28 pm
jaclaz
(@jaclaz)
Community Legend

What about a swarm of underwater drones? roll
http//fusion.net/story/37975/watch-41-underwater-drones-swarm-together/

jaclaz

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Posted : 17/01/2017 1:22 am
RolfGutmann
(@rolfgutmann)
Community Legend

The case turns interesting by the question of economics of resources. If the content of the suspect's
mobile unknown the case is comparable to the San Bernardino case. How would you make this decision based on uncertainty?

At least in Law Enforcement highly uncertain decisions have to been made e.g. due to high public opinion pressure like the colleagues at Kanton Aargau, multimurder Rupperswil had to make (million CHF case).

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Posted : 26/01/2017 9:45 pm
RolfGutmann
(@rolfgutmann)
Community Legend

As a conceptional approach we decided to engineer with the Worst Case Scenario WCS.

For this we expect a river flowing so fast and deep that divers get out of action. Letting flow an Underwater Video Ray UVR results in a cable-based (by ropes) solution. By first based on the operators last eNB logs calculated splash zone there has to be mounted a temporary dual-rope RC-controlled and GPS-tracked River Crossing Rover RCR running on the dual-rope across the river. Inside will be a Tether Management System TMS for the UVR.

Lets stop here. You may say There is no chance. Ok, this we know too.

Few aspects to take into consideration. A smartphone falling into water in almost every case tends to go downwards. Only if speed of water so high the horizontal vector gets longer and the vertical gets shorter. But after a certain time the device will touch ground.

So before letting into water the UVR we would have to sense and map the underwater stream to find out in - aware all these aspects are based on theoretics and unsecure - which direction at a certain point in-river the device would go. Next it would be helpful if we had the bathymetric actual River Underground Profile RUP for lets say 200 meters downstream distance. Therefore its obvious that we need a RUP dataset to load into the Geomatics Simulation Platform GSP. Time is critical I know. So all mobile or real-time transmission from the Sonar Swimming Unit SSU containing an Inertial Measurement Unit IMU running from the rover. The key for this Mission Impossible is preparation as all time-critical missions are.

Ok, now its up to you What has to be done for proper preparation? Hang-in and talk your mind.

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Posted : 29/01/2017 9:53 pm
RolfGutmann
(@rolfgutmann)
Community Legend

Consulted hydro experts told us that a video system will fail if there were strong rain hours before or the algaes growth in-water was too high. We are unsure if the VideoRay

http//videoray.com/homepage/new/professional-rovs/videoray-pro-4/standard-base.html

indesigned we should drop in favour for WCS. Did you make good experience with this system?

ReplyQuote
Posted : 30/01/2017 6:10 pm
hcso1510
(@hcso1510)
Active Member

You could use VLR location to interrogate a mobile.
SS7 has this feature carrier to carrier under agreements.
We have access as goverment to it for location. Depends on which country and carrier you have.

Techinically, you could always locate a mobile in the world.

Droopy,

Curiosity got the best of me so that I have to ask. What is VLR? If it is the Visitor Location Registry that couldn't you interrogate the HLR, or Home Location Registry.

I do know one case where a VLR registry resent was utilized along a time distance formula and some known facts to locate a vehicle that went into a body of water. While this is something that may not work in the majority of situations everything lined up in this one.
If you hit me up with a PM I can go into greater detail, but I would rather not put everything I know about this in the forum. Suffice it to say that within CDR's there is often times evidence that we normally overlook and its not like the Telco's are furnishing us with the questions to ask.

Other than locating the mobile through the cellular network have you ever looked at the data that you can self generate through Google? I've not considered anything underwater, but I do plan to compare this data against cellular data in the near future.

It's just something else to consider.

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Posted : 30/01/2017 9:42 pm
RolfGutmann
(@rolfgutmann)
Community Legend

We definitely drop the UVR and focus on a bathymetric LiDAR for the riverbed topography.

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Posted : 30/01/2017 11:54 pm
RolfGutmann
(@rolfgutmann)
Community Legend

Who has experience with feeding overlapping data from an Acoustic Doppler Current Profiler into MatLab/SimuLink?

https://eau.public.lu/pictures/photos/photos/jaugeage_ADCP.JPG

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Posted : 31/01/2017 4:29 pm
RolfGutmann
(@rolfgutmann)
Community Legend

ADCP short intro

https://www.whoi.edu/page.do?pid=8415&tid=7342&cid=819

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Posted : 31/01/2017 4:34 pm
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