
Startup uses disruption of Earth's magnetic field for indoor positioning - regandersong
http://www.arcticstartup.com/2012/07/09/new-indoor-navigation-startup-uses-disruption-of-geomagnetic-field-from-buildings
======
mmaunder
If you're navigating on a boat, every boat has it's own deviation chart. When
you then use the compass you factor in variation (what the chart says the
difference is between mag north and true north) and the personalized deviation
chart for that boat.

To set this up, some guy comes down to the dock, takes your boat out, does a
few 360's with known landmarks in site and compiles a table of how your boat's
compass varies from standard magnetic north. Big things like the engine,
generator, keel, etc will influence what your deviation chart looks like.
Usually it's less than 4 degrees at each point of the compass IIRC.

So every place in the world has metal objects that create that place's own
distinct deviation from where magnetic north should be. So perhaps that's what
these guys are using. A known table of variation and then looking at the
deviation.

What I wonder about is what happens when someone turns on a 12 amp vacuum
cleaner, a monitor nearby goes into powersaving mode, someone moves their
laptop or someone with their own cellphone walks past. These things emit
magnetic fields, so I wonder how they've solved the problem of the local
deviation changing constantly.

~~~
baddox
> What I wonder about is what happens when someone turns on a 12 amp vacuum
> cleaner, a monitor nearby goes into powersaving mode, someone moves their
> laptop or someone with their own cellphone walks past. These things emit
> magnetic fields, so I wonder how they've solved the problem of the local
> deviation changing constantly.

Are any of those magnetic disturbances even within an order of magnitude of a
smartphone's compass threshold? I'm surprised that the disturbance from a
skyscraper's skeleton would be detectable, and a computer monitor seems like
even more of a stretch.

~~~
kmm
It's clear some disturbances must be measurable because as I walk around the
room, the magnetic field measured by my smartphone constantly changes and
since the magnetic field of the Earth is practically uniform over small
distances, this must mean the disturbances come from my surroundings.

However, when toggling some apparatuses in my room, nothing happened. My
laptop doesn't have a hard drive though, but even only centimetres from it, no
change was measurable. Neither did anything happen near my lamps or the AC/DC
transformator. The only place I measured a difference (<10%) was on the stove
(why yes I'll put my smartphone worth hundreds of euros on a hot stove).
However, this faded into the background at a distance of about 10 cm.

------
DanielBMarkham
I have a small site dedicated to providing information about gps/cell phone
tracking. As part of that, I've been doing a bit of reading about cell phone
tracking capabilities.

It amazes me that we are turning our phones into better tracking systems than
we've ever used on wild animals. Whether it's sound fingerprinting, gps, WiFi
tracking, or now magnetic disturbance tracking, your phone's location services
is getting so it can tell within a few feet where you are at all times. (By
2016 FCC regulations make it a requirement that all phones locate themselves
within 100m or so)

This has amazing potential for startups. If your phone knows you are at the
gym, it can start your workout routine. If you are at the library, it can
decrease the ringer volume. Now with inter-building location ramping up, the
opportunities will only increase.

On a related note, this information can be requested by law enforcement
without a warrant. Last year cell carriers handled over a million such
requests. [http://www.nytimes.com/2012/07/09/us/cell-carriers-see-
uptic...](http://www.nytimes.com/2012/07/09/us/cell-carriers-see-uptick-in-
requests-to-aid-surveillance.html?_r=1&hp)

People wearing little electronic devices that allow law enforcement to
determine their position and travel patterns over any period of time just by
filling out a form and without a warrant. If you had told me 20 years ago this
is where we'd be, I would have called you a paranoid nut-job.

~~~
stcredzero
The kicker will be when they can do this, even when we've flipped the off
switch. For now, there's always the off switch.

~~~
DanielBMarkham
One of the things I was curious about is whether the phone can be enabled
remotely by the telco. I found conflicting information on the web. I suspect
it can, but this is not something the carriers want to talk about. Just a
suspicion, though. I imagine what happens 99% of the time is that the user
doesn't want anything to do with tech like gps tracking, but then they find an
app that does something cool, and it things like gps to be turned on in order
for it to work. So in a way, just like Facebook is destroying privacy by
"helping" folks share, many apps are destroying the anonymity of location and
travel by "helping" folks with cool apps. That kinda sucks. Wish the situation
were different.

Note that location services comprises many different technologies, not all of
which can be turned off. Many of them are required for the phone to operate.
The upcoming FCC regs, for instance, require 100m self-locating ability to
always be on. I guess for things like 911 service?

Speaking of paranoia, there's also rumors that the FBI/black helicopter/MIB
bunch can actually power-up your phone remotely, especially with some models.
This sounds completely out-of-left-field to me, but who knows? Court docs show
they can use your phone as a listening device even when you're not calling
somebody, so I wouldn't put other things along these lines past them. There's
probably a good reason Osama Bin Laden refused to have anybody associated with
him possess a cell phone, whether it was used, had a battery in it, or not.
Seems like I read something somewhere once about illuminating electronics gear
with microwaves, then reading the signature of the radiation emitted. But it
could have been in a pulp sci-fi novel. As I said, it's difficult to tell
where reality ends and paranoia begins with this because reality is quickly
catching up to the paranoia of just a few years ago. Who would have imagined
sub-meter resolution on where you are? That's almost accurate enough to tell
if you're wearing the phone in your jacket pocket or on your belt. Crazy
stuff.

~~~
mindslight
I would think the capability of having an Off phone receive a radio signal to
turn itself On would require pretty deliberate hardware design.

I do remember reading about locally fingerprinting an Off phone based on its
passive radio response, and this seems feasible.

When the phone is On, total location privacy is out the window, as Ma Bell
always knows what towers you're near and can triangulate. Everything else
you've said can be (and probably is) implemented in invisible layers of
software.

End-to-end privacy would be a nice step forward, but assuring this requires an
auditable interface between the radio transceiver and the computer/sensors.
Any fix for the location problem involves decoupling identity/billing from the
physical infrastructure.

~~~
freehunter
> _I would think the capability of having an Off phone receive a radio signal
> to turn itself On would require pretty deliberate hardware design._

Wake on LAN (WoL) is a pretty common feature for network chipsets. I don't
know anything about mobile networks (so take this as the semi-educated
speculation that it is), but it wouldn't be a stretch to imagine WoL over 3G.
It wouldn't have to be a feature advertised to end users of the SoC.

What it comes down to is "what does 'off' mean on a cell phone?"

------
dazbradbury
What happens if there are large items which move and cause changes in the
localised magnetic field readings?

Things such as lifts, vehicles, regularly changing stock levels... Or are
these all considered negligible?

~~~
bhousel
Read the link in pierrebouchet's comment:
<http://news.ycombinator.com/item?id=4217838>

From 5.4.3, it actually looks like this kind of magnetic positioning system
works _better_ in an indoor environment with lots of magnetic perturbations.
This method measures where the person has moved, not where they currently are
against a fixed constellation (like GPS). I'm guessing you would need to
activate the data collection at a known waypoint (e.g. the front door of a
business) and then it could track your movements around a magnetically
perturbed space.

~~~
pvarangot
Those are stationary perturbations they are talking about, the ones they use
to map the region. Your parent refers to moving perturbations, such as
vehicles or electric motors.

An underground mine is really really really different to a subway network if
you are only looking at it magnetically.

------
Gring
It apparently needs the user to move to get a position lock.

This will not work well with the typical use case: user is in a shopping mall,
needs to go to the bathroom, wonders where the closest one is and where he is,
stops walking, opens his phone and starts the app.

Expected outcome: the app says "toilets are 50 meters to the right".

If the app now tells the user "I have no idea where you are. Please walk in a
random direction in a straight line for 20 meters and I will try to find out,
then tell you where you are and where the closest toilets are, which means
that you might have walked in the wrong direction to begin with", the user is
not really happy.

~~~
a-priori
If this causes a negligible drain on the battery, then the device could
passively record the magnetic field at all times into a circular buffer. When
they ask where the toilets are, the device can check the recent data to
immediately figure out where they are.

------
terhechte
I really like this new approach to the positioning problem, especially since
it doesn't require setting up wifi or shooting satellites into orbit.

Does anyone know why this couldn't be used for outside positioning, much like
GPS? Is the information not detailed enough, or do we lack good enough sensors
to detect the fine-grained differences especially given all the
electromagnetic noise that modern cities for example create.

Edit: I just realized it's probably also because somebody would need to create
a world-magnetic-field map, much like the street view cars driving all over
the world.

~~~
defrost
Which we have, not only is there a coarse scale global magnetic field model
(two versions, in fact) there are detailed high resolution maps for large
areas of the world (eg: all of Mali, all of Australia, most of Canada, much of
the central 'stans) where mineral exploration has taken place.

The positioning is complicated by the drift over time (there's a "new" global
model every five years and for specific times & locations interpolation is
performed) and fluctuates daily (as the Earth turns there's a diurnal pulsing
in the induced magnetic field).

This is where "a bit of signal processing" comes into play.

The good news is the maths, the field testing, and the application of it is
all a good 50 years old.

Typical exploration mapping company:

[http://mcpharinternational.com/services/mining-
exploration/a...](http://mcpharinternational.com/services/mining-
exploration/aeromagnetics-magnetic-gradiometry)

High resolution gridded geophysics for the Northern Territory, magnetics,
gravity, radiometrics, etc:

[http://www.nt.gov.au/d/Minerals_Energy/Geoscience/index.cfm?...](http://www.nt.gov.au/d/Minerals_Energy/Geoscience/index.cfm?header=Territory-
wide%20and%20regional%20maps)

~~~
terhechte
Thanks! Very interesting.

------
cwiz
Whoa :) This is very clever. I've been working on indoor positioning quite a
long time already and might give this a try. No WiFi -> no extra WiFi hardware
costs -> widespread use

This technology might disrupt indoor advertisement.

------
lbotos
I guess this would be a relatively relevant place to ask, does anyone know of
an affordable technology that can be used for precision (inches) tracking of
8-36 items indoor or out? The caveat would be affordable. The use case would
is BMX Racing. Scoring is still done by hand! I've looked into RFID tagging
but the docs and manufacturer's specs are all over the place. Any ideas?

~~~
18pfsmt
Note: I will keep my comments to passive RFID (non-battery powered tags) and
leave aside active RFID commonly used for toll roads, shipping containers,
etc.

RFID is actually a family of technologies, typically defined by ISO standards,
and operating over several distinct frequencies: 134kHz (LF), 13.56MHz (HF),
and 900MHz (UHF). LF and HF use inductive coupling between the tag
(transponder) and reader (transceiver) while UHF uses capacitive coupling.
Theses technologies do not allow one to know a specific distance, but rather
when a tag is in the field or not. So, when Wal-Mart uses UHF tags on their
pallets, they don't know where the pallet is exactly in their warehouse, they
simply know when the pallet has passed through their loading dock. I've seen
some triathlon timing systems use UHF RFID, but they still use cameras in case
of close finishes.

Hope that helps.

~~~
lbotos
Thanks! I've seen some timing systems that are used in triathlons but the main
problem was making a field that was 25-30 feet width but a tight spread (1
foot). Do you think active would fair better in that respect? Last time I
checked it seemed so but it also jacked up the price a bit. I know that for
Olympic BMX they are using some type of active transponders but I can't think
that any commercially available solution would be accurate enough. I assume
they have to be doing camera checking too but for .000 second split times even
a foot spread seems like a wide margin of error.

~~~
18pfsmt
Given the granularity in timing (i.e. 0.000 sec) you are looking for, I don't
think active would help; and, the tags are certainly more expensive, though
reusable.

~~~
lbotos
I'd settle for .00 but if I'm not mistaken the Olympic level reports .000 with
some type of active transponder:

<http://www.youtube.com/watch?v=vb_UXJVK7iM>

------
AlexMuir
I just don't see indoor navigation as a huge problem to be solved. And this
seems a phenomenally complicated solution to a small problem.

GPS works because _outside_ is an enormous, unfamiliar place with tens of
billions of destinations. Inside is small, relatively familiar, and even a
large building has, at most, hundreds of destinations.

Just watching the demo, it's super cool and super intelligent. But it doesn't
look like it can do direction - it can only tell direction after you've walked
a certain distance. How will it cope with large magnetic things that move - eg
Forklift trucks, vehicles, trolleys, wire cages etc.

I don't buy it. Ikea is the only potential place I could see this being of
use, and there's no way anyone's going to bake in an extra sensor to a
smartphone on the offchance. Look how slow adoption NFC has seen and that's a
MASSIVE problem with multiple applications and a clear financial incentive.

~~~
crisnoble
Working for a medium size manufacturing plant that wants to get a handle on
movement of goods and people, I can tell you that this technology would be a
game changer. We can't afford to use RFID and 1m accuracy of Wifi positioning
is not worth the hassle. This site says they can get .2m accuracy, no extra
infrastructure required, we will be watching this technology very closely. It
is a lot easier to stick an iPod touch in someone's pocket than install RFID
infrastructure.

~~~
skyahead
To locate things with this technology, you need a smartphone on them. How can
you use it on goods?

~~~
crisnoble
I am talking about movement of goods within a single warehouse. We could stick
an iPod touch on the bottom of a pallet/box for a couple days. If the tech
takes off maybe someone will invent a ruggedized tiny piece of hardware that
just has the compass and wifi data transmission built in.

------
PanMan
How does this work? I understand if you know the true north and the magnetic
north, you can get the difference, but I assume a compas only can measure one
of them (the magnetic one). How do they determine the 'fault' in the signal
with just 1 signal?

~~~
flog
And what what if the stock is magnetic? ("Where's the fridge magnet isle?")
... and doesn't the earths magnetic fields change also?

There's a number of questions I'd have about the stability of the data being
collected and how quickly it'd go stale.

~~~
wpietri
Every phone using the app can contribute to your map data. If you combine
magnetic data plus wifi data plus user behavior data, I expect you'd be able
to continue to provide good 3D data to users.

I'd bet the hard part is getting building owners to update things regularly.
Who's going to remember to change the map when the grocery store moves the
cereal from aisle 2 to aisle 7?

~~~
flog
You raise another point I haven't thought of: 3D. People are different
heights... surely that changes the fields too. Interesting problems to be
overcome.

------
sbanach
I always thought a reasonable solution to this problem was triangulating via
wifi and bluetooth signal strength from access points of known location. I
tried it as a weekend project a few years ago but random fading was a killer
and I never got it to work that well. Seems like it should be possible though.
Are there good reasons not to do it this way?

~~~
defrost
Not everywhere has wifi and bluetooth (yes, places exist outside of the wired
world) and from the article it seems that an application area of interest is
underground mining where transmitting radio through tunnels is already
problematic.

------
torstesu
Seems similar to the technology demonstrated in this article [1]. However, it
does seem that IndoorAtlas Ltd had a better opportunity recognition radar.

[1] [http://www.newscientist.com/article/mg21328516.200-apps-
glow...](http://www.newscientist.com/article/mg21328516.200-apps-glowing-
arrows-guide-you-around-a-new-building.html)

~~~
obtu
Another difference is that the use of a built-in compass eliminates the need
for a badge.

------
robomartin
With reservations --simply because I don't know their details-- I'll say that
this is nothing new at all and it could be the makings of another case of
patent abuse.

Local changes to the magnetic field have been used for quite some time for
purposes such as oil exploration. I remember talking to an old geologist/oil
man about twenty years ago as he went about locating candidate areas to
explore based on these fluctuations. He explained that they'd use
magnetometers to map out underground "cracks", deposits and other features. To
go from that from generating local location data by overlaying a map of some
sort (whether it is a building or something else) is nothing less than
trivial.

If you have any experience sailing you may have also witnessed the effect of
large sunken metallic objects on the compass. Again, you could "navigate" by
these effects "Hey we must be passing over the SS-Sunken Ship".

Gotta love patents.

------
Zenst
Given that mobile phones have wires and electricity then they are creating
small magnetic waves which will impact others. That all said this technolody
is very suitable for underwater GPS were a GPS signal does not penetrate the
water due to weakness and how bad radio travels thru water in general.

So given that I would have to questions if the military don't already use
something very similiar in submarines. Lets say I'd be very supprised if this
was not being already utilised in some form or another in that feild.

------
darkstalker
A cool use for this would be an app that tells you the position of merchandise
inside a supermarket

------
zacharycohn
The big problem/timesink here is mapping.

Could this solved by combining the mapping process with the quadracopters that
can autonomously fly through and map a building?

------
deepGem
I did get an incidental 500 server error, guess the server is getting
bombarded. Keep an eye folks.

------
skyahead
Does this need users to hold smartphones flat? If so, how inconvinient!

------
harryf
The demo of mapping inside the supermarket - real world Pacman...

