×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Ask Dr. Ramsey Faragher About Navigation/Positioning Technology

samzenpus posted about 2 years ago | from the where-in-the-world dept.

Technology 104

Dr. Ramsey Faragher graduated from the University of Cambridge in 2004 with a first-class degree in Experimental and Theoretical Physics. He then completed a PhD in 2007 at Cambridge in Opportunistic Radio Positioning under the direction of Dr. Peter Duffett-Smith, a world expert in this field. He is now a Principal Scientist at the BAE Systems Advanced Technology Centre specializing in positioning, navigation, sensor fusion and remote sensing technologies in the land, air, sea and space domains. We recently covered his NAVSOP project, an advanced positioning system that exploits existing transmissions such as Wi-Fi, TV, radio and mobile phone signals, to calculate the user’s location to within a few meters. Dr. Faragher has graciously agreed to answer any questions you may have about NAVSOP, the future of GPS, or what a theoretical physicist puts on his business card. Ask as many questions as you like, but please confine your questions to one per post.

cancel ×
This is a preview of your comment

No Comment Title Entered

Anonymous Coward 1 minute ago

No Comment Entered

104 comments

question (0)

Sparticus789 (2625955) | about 2 years ago | (#40564181)

Has this been tested in remote areas? For example, middle of the ocean, Saharan Desert, Antarctica?

Re:question (0)

Anonymous Coward | about 2 years ago | (#40565295)

Stupid question. It's called opportunistic because it provides alternatives to GPS when given the opportunity. It doesn't pretend to be a global replacement that works everywhere.

Re:question (1)

Sparticus789 (2625955) | about 2 years ago | (#40566085)

It's a good and legitimate question for people who venture away from cities and urban centers to locations which have no radio or cell phone coverage. Those are areas that I frequent and I asked the question to understand HOW close you would have to be to a electronic signal to receive a location from this method, i.e. how sensitive of a device can be made with this method.

Most Surprising Correction? (5, Interesting)

eldavojohn (898314) | about 2 years ago | (#40564225)

I'd imagine a lot of positioning calculations involve accounting for or adjusting for known effects or noise. For example, accounting for general relativity in GPS. What is the most surprising correction you've ever come across (even on an exam or done in theory)? Have you ever found yourself saying "I didn't think that could affect the calculations so much."

Re:Most Surprising Correction? (0)

Anonymous Coward | about 2 years ago | (#40565919)

I see what you did there. Breaking the "one question" rule by neglecting the second question mark.

Re:Most Surprising Correction? (1)

billybob_jcv (967047) | about 2 years ago | (#40567557)

When you are talking about pseudoranges measured in nanoseconds, darn near everything is significant. In research, surveying and other high-accuracy positioning systems, the Ionosphere, Troposphere, multipath, antenna-to-receiver cable lengths, the data acquisition and computation time and several other effects are all modeled.

For myself, I think the most surprising was needing to pay attention to the number of significant bits in the mantissa of real and double precision numbers used in the calculations. I couldn't figure out why I couldn't exactly match the results between the embedded processor in the receiver and my software model, and I finally figured out that there was a 1 bit difference between the number of bits assigned to the mantissa of the double precision floating point formats in each system. I finally figured it out by noticing that the value for the radius of the Earth at the equator (a fixed constant in both models and carried out to a ridiculous number of significant digits) was not exactly the same in the two systems.

Suede Oranges? (0)

Anonymous Coward | about 2 years ago | (#40567757)

When you are talking about pseudoranges measured in nanoseconds ...

Mmmmm super fast suede oranges.

Happy Friday from the Golden Girls! (-1)

Anonymous Coward | about 2 years ago | (#40564227)

Thank you for being a friend
Traveled down the road and back again (with GPS)
Your heart is true your a pal and a cosmonaut.

And if you through a party
Invited everyone you ever knew
You would see the biggest gift would be from me
And the card attached would say thank you for being a friend.

Re:Happy Friday from the Golden Girls! (-1)

Anonymous Coward | about 2 years ago | (#40564339)

so i was at the supermarket the other day, right?, in the produce section, and i walks up to this guy, and i says, i says to the guy, i says to him, i says, "excuse me, but is that your nose or is it a banana?" and the guy is all like, what?, and so i says, i says again, i says, "excuse me, but is that your nose or is it a banana?" and then the universe dissolved around me and i was left floating in the vacuum of space, and so i walks up to the vacuum of space, and i says, i says to the vacuum of space, i says, "excuse me, but are you the vacuum of space, or are you a banana?"

Indoor Positioning System (4, Interesting)

gshegosh (1587463) | about 2 years ago | (#40564253)

What kind of accuracy is possible to achieve using NAVSOP - or other systems you know of - if I can place stuff like APs, mobile phones, etc. myself in a factory area? Do you have methodology for designing placement of such devices so positioning accuracy is reached at every point? How low can one get with costs of such solutions?

Re:Indoor Positioning System (1)

MobyDisk (75490) | about 2 years ago | (#40566403)

Let me add why this an important the next step in indoor robotics. The Roomba and similar robots and toys have avoided this problem by operating blindly, or by using limited aids such as virtual walls or markers. But these parlor tricks aren't good for long-term intelligent indoor robots. They need to not just avoid obstacles, but also find the refrigerator, skip vacuuming the garage, and know to use different cleaning fluids on the kitchen ceramic tile -vs- the dining room hardwood. They should stay away from the dog's cage and the cat's litter box. Flying robots need to avoid ceiling fans. etc. etc.

Re:Indoor Positioning System (1)

gshegosh (1587463) | about 2 years ago | (#40567977)

Indeed, though I think it's easier at home/flat -- you could just place a few dozen RFID tags as markers and be done with it. On the other hand, at industrial level it is not a viable solution and it would be great if low-cost solution existed, based on placing cheap APs instead of expensive laser stuff, etc. and still obtain accuracy of, say, 10 centimeters.

Re:Indoor Positioning System (0)

Anonymous Coward | about 2 years ago | (#40574389)

There are more intelligent robots such as the Neato XV-11 and the Willow Garage Turtlebot that you can buy that make use of depth sensors to do SLAM in an indoor environment. The Neato for example scans the house it is in with a rotating laser scanner and then does a single pass with a vac (It's also a relatively easily hackable platform). The Turtlebot uses a Microsoft Kinect to do the same. What NAVSOP could provide is the ability to localize in environments without maps.

Re:Indoor Positioning System (1)

Anrego (830717) | about 2 years ago | (#40568969)

Damn.. wish I had mod points.. would really like to see this one answered!

In-Building and Underground GPS (4, Interesting)

GeneralTurgidson (2464452) | about 2 years ago | (#40564309)

Will there ever be a way to accurately use GPS without open sky access in a building or underground?

Re:In-Building and Underground GPS (1)

poetmatt (793785) | about 2 years ago | (#40564719)

Aren't people working on indoor GPS via triangulation of wifi points, mobile points, etc? I thought I read up on something about that the other day similar to http://www.gadgetbox.msnbc.msn.com/technology/gadgetbox/get-ready-indoor-gps-tracks-your-every-step-735448 [msn.com] . Not sure if that's an alternate to your question or not.

Re:In-Building and Underground GPS (2)

witherstaff (713820) | about 2 years ago | (#40565429)

Yes, I know Western Michigan University Library technology staff have an in-house built app for an in-out board that uses wifi signal strengths to locate staff. It's been active for over a year. It does have to be initially trained for any different location. Not hard with the push of a button. Also android only, iphone doesn't let you sniff information on other wifi nodes, just the one you're connected to. I don't have the published article reference offhand but there are a variety of papers on similar ideas.

Re:In-Building and Underground GPS (1)

MobyDisk (75490) | about 2 years ago | (#40566443)

This approach is nifty, but is too limited for general purpose robotics use. It isn't accurate. It requires multiple wifi hotspots. It doesn't let you move your wifi routers or change them out - even a firmware update the changes the power output or the channel (which some routers do automatically) might break it. It requires training.

Re:In-Building and Underground GPS (0)

Anonymous Coward | about 2 years ago | (#40566927)

|Sure it's so easy it's laughable.

1st stick a pole in the ground with a little transmitter on top of it, which transmits it's exact location continuously. As your vehicle passes it can pick up the transmission. Put these, say every 5-10 miles along the highway. 2nd In the vehicle this info is picked up and converted to your current location. The rest of the distance until the next xmitter calculates less/more any mileage your vehicle travels.
This would work through tunnels under bridges or any other obsticle in the way.

Privacy (4, Interesting)

girlintraining (1395911) | about 2 years ago | (#40564311)

It would seem that to use this technology, the client would need to have a much larger datastore than with GPS: Whereas only the positions of the GPS satellites need to be known to make a calculation, the dataset here is in the many thousands to millions. In addition to the data required for map storage, it would seem any implimentation of this would require an internet connection to download the data in a geographically-restricted fashion. This opens the door to privacy issues that standalone GPS clients do not have.

How do you plan on addressing the privacy issue with your product?

Re:Privacy (1)

afidel (530433) | about 2 years ago | (#40564661)

Huh? GPS units have had GB's of map data for almost a decade, it's not like in the 90's where you had to load a new map set if you were traveling more than a few hundred miles. Compared to the full map set for say North America the list of radio/cellphone towers and locations is trivially small (although the cellphone ones do change somewhat regularly so you'd want a way to update the database).

Re:Privacy (2)

kav2k (1545689) | about 2 years ago | (#40564831)

I think you're misunderstanding the point. OP talks about finding bare coordinates, not position on a map. Not all applications of GPS are tied to the map data, and map data is "external" to finding your position anyway (but can be used to correct it with assumption like "you're on the ground and on a road").
Sure, maps are big, but all the data needed to get raw coordinates is quite small. But with this system, you need a database of all your new "reference points" - cell towers, wifi, etc.
What's worse, this data becomes obsolete fast, while GPS constellation is not radically changing often, and all (most?) changes are communicated automatically via almanac data.

Re:Privacy (1)

Amouth (879122) | about 2 years ago | (#40564839)

His question is more on the map being required to locate it's self, your comment is about maps which you can show your self on after you know where you are. They are completely different sets of "maps".

Dev Kit? (0)

Anonymous Coward | about 2 years ago | (#40564317)

Any chance of development kits being released in the near future? Indoor localization is a very tricky problem, and if I can just use somebody else's chip/SDK/setup, then I'd prefer to go that route.

Precise Positioning in Deep Space? (5, Interesting)

eldavojohn (898314) | about 2 years ago | (#40564335)

Something that surprises me is that we're so obsessed with the exact positioning of things on Earth but at great exo-solar distances, we seem to be okay with measurements to the nearest million light years. A couple days ago I read about a new method devised to measure location to within a few hundred meters of something 200 million kilometers away from Earth [aalto.fi] and it struck me as odd that more effort isn't put into this. While the practicality of Earthbound work is far greater, the implications for physics and verifying theories seems to be an obvious benefit for better positional measurements in space. I know satellites and objects near Earth are heavily measured but why isn't there more attention paid to precision of deep space objects? What problems prevent sensor fusion from being applied to space? Too much noise? No way to actually verify your results?

Re:Precise Positioning in Deep Space? (1)

DerekLyons (302214) | about 2 years ago | (#40566271)

I know satellites and objects near Earth are heavily measured but why isn't there more attention paid to precision of deep space objects?

For those objects for which high precision is required - there is. For those objects for which it's not - there isn't. There's surprisingly few of the former, and many, many, of the latter.
 
The ultimate problem however is that the input data is (relative to what we're used to for terrestrial applications) generally of fairly poor quality. Thus you need either a great many observations, or a great many observers, and considerable computation and analysis... And at the end of the day, it doesn't matter so much if galaxy M189432 is 10x10^19 light years away, or 10.0001x10^19 light years away. Or at least it doesn't currently matter enough for anyone to go to the effort.

Re:Precise Positioning in Deep Space? (1)

ddrueding80 (1091191) | about 2 years ago | (#40567823)

Triangulation? All of the methods and techniques described above require your frame of reference to change significantly relative to the signal sources.

Re:Precise Positioning in Deep Space? (0)

Anonymous Coward | about 2 years ago | (#40575067)

Let me get this straight. You read about a new method devised to measure the location, to within a few hundred metres, of something 200 million kilometres away, and you are still very concerned that not enough effort is being put into it? At this point, I think you should explain what you personally plan to do about the issue.

advert (-1)

Anonymous Coward | about 2 years ago | (#40564377)

souns like an advertisement for him, the entire post talks abour him and his degrees, what value is he really adding to slashdot?

Re:advert (1)

element-o.p. (939033) | about 2 years ago | (#40565531)

He's a PhD and expert in a technical field who is sharing his expertise in that field, and you, Mr. Coward, are asking what value he brings to /.?

Untapped resources (1)

Anonymous Coward | about 2 years ago | (#40564407)

With the improvement, both in time and coverage, that using WiFi and cell tower triangulation adds to straight GPS or A-GPS, and with NAVSOP going even further, what signals (or aspects thereof), in the EM spectrum or otherwise, remain untapped? What's the next step in improving time, coverage, energy efficiency, affordability of location systems?

Automation? (3, Insightful)

eldavojohn (898314) | about 2 years ago | (#40564417)

How much of this can be done automatically and how much of this must be hand guided? For example you talked about [slashdot.org] fingerprints changing over time and being used only as a guide. Is there a measurement or confidence variable that you can employ to automate when the fingerprint is still valid or has morphed too much? Or is that something that a human overlord must monitor and do research to notice that a new apartment building has just been opened and there are now hundreds of new signals? It feels like you are using an open domain that could have outliers and irregularities that require a human to clean the data before it can be trusted to give you low false positives and true negatives. What statistical methods do you use to overcome these sort of real world problems so that your system can be put anywhere and work?

your best guess on the GPS successor? (5, Insightful)

Sem_D_D (175107) | about 2 years ago | (#40564427)

Hi, Dr Ramsey!
What is your best estimate as to what is the US DOD's current GPS backup system?
IIRC Obama cut the budget for LORAN around 2010 and till then the system was financed with the explicit explanation and purpose - GPS backup. But no more...
I am currently teaching ECDIS systems to mariners and I always emphasize the weaknesses of GPS under jamming. Ever since Selective Availability has been switched off, the jamming topic pops up more and more as a soft spot of the whole process, so I think we are not fooling ourselves that the US would let down such a gaping hole in its systems uncovered...

Re:your best guess on the GPS successor? (1)

girlintraining (1395911) | about 2 years ago | (#40564907)

Because civilian aircraft and many other mission-critical functions depend on selective availability not being enabled, it's highly unlikely they'd use it domestically.

The other argument against SA is that there are severalmethods of interpolating the GPS signals to achieve a lock that don't require decoding anything but the almanac. So mucking up the signal intentionally doesn't have to affect equipment, as long as it is designed to use the more sophisticated methods of acquiring a lock. So if you're a terrorist trying to build a missile that flies by GPS, you're in business, you'll just have to design the circuit board yourself, not use COTS equipment. Because of that, any regular use of SA would eliminate its primary function -- any hostile force would simply adapt their equipment.

GPS jamming on the other hand, there is not much anyone can do about. The signal is actually below the noise floor, and it requires LOS because of the very low signal strength. All GPS satellites also use the same narrow frequency band, so it's trivial to build a jammer that can knock out any signals to the horizon on a modest budget. The many sensor model would be more resiliant to this kind of narrow-band emission, but because the database (by necessity) has to be public, you can tune a jammer to selectively block many frequencies for a modest power level bump. And don't forget that you can still create a high power broad-spectrum emitter using very simple equipment; a tesla coil with an RF component is sufficient to screw with electronics for miles around, even those without a discrete RF component (like cable tv).

Simply put, civilian equipment will be vulnerable to jamming for a long time to come yet; only rapid frequency shift cognitive radio (which is what the military uses) can be said to be jam-resistant. You don't have the budget for that kind of equipment, and even if you did, the FPGAs you would need for the front-end are classified as munitions and cannot be exported, and only the government right now can purchase them, or special licenses available only to companies. But hey, if you have a chip fab plant, and a team of engineers, you might be able to put something together. Maybe.

Collaboration? (0)

Anonymous Coward | about 2 years ago | (#40564471)

I have seen a description of the new Sirfstar V chips doing much the same as you describe. As they are also in the vicinity of Cambridge, is there some cross-pollination of ideas here, or is theirs a completely separate system?

Regulatory approval? (3, Informative)

k(wi)r(kipedia) (2648849) | about 2 years ago | (#40564509)

Wouldn't this thing require a whole slew of regulatory approvals since you'd be fishing for different types of signals? Or would this involve mere processing of data already available to, say, the smartphone armed with this technology?

Directing an air strike (0)

Anonymous Coward | about 2 years ago | (#40564525)

People have used opportunistic radio transmissions to navigate since the beginning of radio. For instance, the Japanese used civilian radio stations to navigate their way to Pearl Harbor.

Back in the day ...

Radio stations could be asked to go off the air. Radio Amateurs would be asked to turn in their transmitter tubes. It was relatively easy to create radio silence.

Now it is probably impossible to create radio silence. The terrorists don't need GPS to guide their drones to their targets.

House GPS (0)

Anonymous Coward | about 2 years ago | (#40564539)

I would like to buy a few devices similar to a WiFi Router that would allow GPS recivers within the confines of my house to have 12 inches or less accuracy. This would be great for interfacing to my phone for home automation like things. Or for house vacumes that are very accurate. Is anyone working on single building high resolution positioning?

Networked? (0)

Anonymous Coward | about 2 years ago | (#40564645)

Would the individual recivers for NAVSOP be linked to each (either remotely or on an ad-hoc basis) in order to better improve the tracking? If so would you be able to model "swarming" of users for modeling of travel patterns?

cheaper solution? (0)

Anonymous Coward | about 2 years ago | (#40564655)

Don't want to sound like a prick, but might be cheaper and more effective to devise a star/sun fixer with a chronometer, a compass, and a star database (like they did for a few hundred years on ships, and still do, but manually with a sextant).
Of course you're screwed if it's cloudy and you can't sight the stars.

Spoofing Use as a Counter Weapon (1)

Anonymous Coward | about 2 years ago | (#40564687)

Global positioning signals are used to help target various weapon systems in the United States arsenal. These signals can be--and have been--spoofed, to mis-direct these devices. Do you see spoofing technology as a meaningful threat to our offensive and defensive capabilities?

How accurate could GPS get? (1)

Anonymous Coward | about 2 years ago | (#40564691)

How accurate could GPS get? Will it be possible to make GPS accurate down to submeter levels? Could we one day get GPS accurate to within centimeters or better?

Re:How accurate could GPS get? (1)

Bob the Super Hamste (1152367) | about 2 years ago | (#40566427)

That exists already but you don't have access to it. Maybe when the European Galileo system comes online and you will. It is suppose to allow centimeter level accuracy if you pay, but is open enough so that everyone can have access to that level instead of just the military.

Re:How accurate could GPS get? (0)

Anonymous Coward | about 2 years ago | (#40576821)

Differential GPS and RTK GPS systems used for surveying can achieve centimeter to milimeter accuracy already.

Gravitational field strength (1)

advid.net (595837) | about 2 years ago | (#40564703)

Does the gravitational field strength could be used also for NAVSOP ?

Maybe slight natural variations, and buildings, underground structures like metro, subways, large sewers can be sensed by gravitational sensors, at least the new ones with atom waves interference...

GPS Coverage (0)

Anonymous Coward | about 2 years ago | (#40564779)

I recently drove from Florida to North Carolina and for a significant amount of time received errors about being unable to find GPS signal. What would it take to improve our GPS coverage.

Re:GPS Coverage (1)

rally2xs (1093023) | about 2 years ago | (#40564893)

An external antenna on top of your car.

Re:GPS Coverage (1)

Bob the Super Hamste (1152367) | about 2 years ago | (#40566341)

Or a high sensitivity antenna in the device. I was shocked at the increased signal strength my newer GPS (has a high sensitivity antenna) has compared to my old one. I have used them side by side and the old one will frequently loose satellite lock in dense cover while the new one doesn't.

Re:GPS Coverage (1)

CompMD (522020) | about 2 years ago | (#40566067)

There's nothing wrong with GPS coverage, your receiver has a problem. It may require a firmware update or an external antenna.

Public Understanding of Your Work? (0)

Anonymous Coward | about 2 years ago | (#40564835)

Dr.: I find science and technology to be endlessly fascinating areas of study, but I know that I am in the vast minority in society in this respect. What do you wish more people understood or appreciated about the science and technology underlying what you do?

Frequencies (1)

Anonymous Coward | about 2 years ago | (#40564881)

Are there other frequencies of EM radiation that would be better suited for navigation than the gigahertz used now?

Map Projection (1)

Anonymous Coward | about 2 years ago | (#40564929)

What is your favorite map projection? (Geeks like to know these things)

Interoperability (1)

ruinevil (852677) | about 2 years ago | (#40564933)

How interoperable are the European and American GPS systems?

Re:Interoperability (0)

Anonymous Coward | about 2 years ago | (#40565567)

Well, there's GPS (American), Galileo (European), GLONASS (Russian) and whatever the new Chinese thing is called (Beidou?). They're not interoperable in the sense that they use different codes and frequencies (but you do understand that each system has a constellation of satellites which orbit with worldwide coverage, right?), but it's not hard to build hardware to receive signals from all the systems with the same antenna, and get position information against all the systems simultaneously. I own off-the-shelf hardware which decodes signals from GPS, GLONASS and Galileo. Beidou is a bit different, as its satellites are geostationary and it only has coverage near China at the moment.

Re:Interoperability (1)

Bob the Super Hamste (1152367) | about 2 years ago | (#40565665)

From my understanding it is possible to have a device that supports the American GPS [wikipedia.org] as well as the Russian GLONASS [wikipedia.org] system and the planned European Galileo system [wikipedia.org]. I have done some checking and it appears that there are some consumer level devices available [amazon.com] that are capable of receiving and processing both GPS and GLONASS signals for faster and more reliable location lock. I would imagine that adding support for Galileo would be simpler as those frequencies are much closer to those used by the US GPS (so much so that if one were to try to jam Galileo they would also jam GPS [wikipedia.org]) than those of the Russian GLONASS system. Personally I would love a device that could incorporate all 3 and be able to a track large numbers of satellites from each as most devices I see that support GPS and GLONASS don't mention how many more satellites they can lock on to or use lots of marketing speak to obfuscate the facts.

Cambridgeshire pub preferences (2)

hotdiggity (987032) | about 2 years ago | (#40565021)

Might I ask your favourite pub in Cambridge and the local area? It doesn't need to still exist.

Sensor fusion (accelerometer etc.) (3, Insightful)

LifeIs0x2A (2615925) | about 2 years ago | (#40565051)

What potential do you see in the combination of these "opportunity" signals (Wifi etc.) that are to be used in NAVSOP and data from sensors like an air-pressure sensor, accelerometers etc.?

Introductory materials about navigation? (1)

tlhIngan (30335) | about 2 years ago | (#40565065)

We all know how GPS works, and even the basics of the math behind it, but where does one find more in-depth mateirals? Like if one were to create a GPS receiver, how to translate those signals into something useful? Not just dumping the equations out and say "solve this" but working step by step through a solution and then adding in corrections like relativity?

Re:Introductory materials about navigation? (0)

Anonymous Coward | about 2 years ago | (#40566565)

In-depth:
  "Understanding GPS: Principles and Applications" by Kaplan and Hegarty, but it will make your head hurt.
  "A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach" by Borre is a more implementation oriented explanation but no substitute for the previous.

Practical examples:
http://www.holmea.demon.co.uk/GPS/Main.htm
http://lea.hamradio.si/~s53mv/navsats/theory.html

Using GPS technologies for encryption (1)

wisebabo (638845) | about 2 years ago | (#40565215)

So, since the GPS satellites and other systems are enmeshing the world in streams of digital data, can a portion of the data stream be used to transmit some sort of key so that it can be proven the receiver was at a specific space-time coordinate?

Like if satellite A was transmitting a continuously varying stream of random numbers and satellite B was doing the same then a receiver could take the product of the "random" numbers that it captured over a short window of time and use it to encrypt and "space-time" stamp it (neat concept, can I patent it?).

If the flow of numbers is sufficiently fast perhaps it would be impractical for a third party to retain and compare all possible products of the numbers sent by all the satellites. (Maybe it'll need another source if random numbers to mix in, say from a natural source like a pulsar?). Then again since I'm not a cryptographer/signal specialist perhaps there is a very simple reason why this won't work.

Re:Using GPS technologies for encryption (0)

Anonymous Coward | about 2 years ago | (#40565675)

Yeah. The bit rate isn't that high. GPS broadcasts the C/A code at about 1Mbps and the encrypted P-code at about 10 Mbps. So it's trivial for me to store a second's worth or more of data from each GPS satellite in view in hardware which is basically free. So I could fiddle the numbers to generate any position I liked that was in view of the same satellites (and I don't need to use the ones near the horizon, so I can put myself anywhere in a several hundred mile radius pretty easily.)

What is the range of frequencies? (0)

Anonymous Coward | about 2 years ago | (#40565301)

Years ago during world war 2, pilots flying at night used dead reckoning, and followed two other signals, one from the north of England, and one from the south of England. One was called cat, and the other mouse. Cat chased mouse. Hyperbolic curves plotted on maps meant that when the signals were a certain distance apart, you were a certain distance from them (and using loop antennas gave a rough direction to each, given that the signal is strongest when the antenna is orthogonal to the EM radiation). It eventually became LORAN. HF radio direction finding usually involves "ELEPHANTS CAGES" like Pusher HF-DF Wullenweber "BULLSEYE" antennas, etc. These are very large because of the physics involved. To keep your unit small, how do you get around these challenges? Can you use HF frequencies or are you limited to VHF/UHF? I ask because the range of some of these signals (WIFI) is very small, cell phone signals are likewise less than 20 miles, TV is good for about 50 miles. When you are at sea, on the sea, unless you get backscattering, you don't get any of these (and the frequencies are too high to refract on the ionisphere, ie no 'skip'). HF will refract, but then we are talking about physics and size. An aircraft can get signals from much further, but you would still rely on a lot of dead reckoning over much of the worlds oceans.

Sensor fusion (2)

Arthur B. (806360) | about 2 years ago | (#40565311)

In order to combine all the sources of information, are you relying on a messy approach, something based on many signature machine learning algorithms (think boosting, SVNs, random forests etc) or are you writing an explicit generative model for the noise and then applying filtering to it, with a particle filter for instance?

Re:Sensor fusion (1)

Arthur B. (806360) | about 2 years ago | (#40565353)

erratum:
In order to combine all the sources of information, are you relying on a messy approach, something based on some classic machine learning algorithms (think boosting, SVNs, random forests etc) or are you writing an explicit generative model for the (trajectory, sensor output) and then apply filtering to it?

Quantum entanglement to improve accuracy (1)

wisebabo (638845) | about 2 years ago | (#40565323)

So I've heard that a problem with the GPS and presumably other systems is that the radio signals are slowed by varying amounts by going through the ionosphere (thus reducing accuracy). I realize that you cannot use quantum entanglement to send (new?) information but does that include the information that a measurement has been made (if not the result)?

So could GPS use entanglement to precisely determine the time of a measurement? I think it's been demonstrated that they can send an entangled photon hundreds of kilometers so it's only a matter of time before it becomes practical to use these devices on satellites.

spoofing (1)

demonbug (309515) | about 2 years ago | (#40565413)

Following the downing of an American drone in Iran the hypothesis was put forward that the Iranians spoofed the GPS signal and convinced the drone that it wasn't where it thought it was in order to get it to land in Iran (I'm not sure if this was ever confirmed). A recent issue of Aviation Week reported on a group I believe in the U.S. working on the same idea, spoofing the GPS signal in a transparent manner to convince an autonomous vehicle that is was somewhere other than its actual location. Would NAVSOP make it more difficult to accomplish this sort of spoofing?

When technology changes (0)

Anonymous Coward | about 2 years ago | (#40565491)

Seems like a great alternative to GPS in most casual situations, or as an addition to it for faster position locks while driving.

The questions I have are:

  1) As technology changes, such as the changing of the cell phone signals to differing frequencies as they increase speed.. ie, 4g, LTE,...etc or OTA TV switching to digital.. Will this still work? Or would people have to replace their "non gps navigation unit" when various signals that this relies on for positioning stop, or change frequencies? We've seen a lot of changes already so we know that things can change very rapidly and perhaps in unexpected directions.

2) What about countries or certain places that don't have the same infrastructure as the US or most of Europe? Or very remote places such as in the middle of a Rainforest (whichever one). Gps would work there as long as you had open view to the sky, but are there enough signals bouncing around (I guess I should say Signal Propagation?) even there for this technology to accurately and (hopefully quickly) give a location?

3) Any, plans perhaps as I mentioned above, on possibly merging the technology with gps as an adjuct instead of as a full on replacement? I think this would be a great boon for mobile navigation, perhaps even saving serious battery life in mobile devices. It could supplement location information when a gps signal becomes weak or sporadically drops in and out (due to the weather or obstructions like bridges, tunnels, big city buildings) keeping the phone from having to boost power to try and find/maintain a gps signal. This would save considerable power and allow navigation to continue until a strong gps lock can be made at lower power levels.

Galactic GPS using pulsars (1)

wisebabo (638845) | about 2 years ago | (#40565539)

So I seem to remember a proposal to use pulsars to provide a sort of galactic GPS. (Pulsars, spinning neutron stars, are extremely stable periodic emitters of radio waves at interstellar distances). I think this might be what an earlier poster was referring to for spacecraft navigation, I believe they were used on the famous Pioneer 10 plaque (with the naked humans) to show aliens where we live.

Anyway, what's the accuracy for this (the previous poster mentions several hundred meters over hundreds of kilometers but I don't know if it's the same system)? Is it as good as (terrestrial) GPS? Will it be good enough to use for the upcoming GAIA mission which will map the 3D location of a billion stars in our galaxy?* (The positioning requirements of that mission are borderline insane!). Is there any way to use these celestial beacons as (another) GPS backup or are the signals far too weak (or unstable or blocked by our atmosphere or are in already used radio bands)?

Sorry about the more than one questions but they're all related. :)

*actually since most (all?) of these pulsars are within our galaxy maybe they are not far enough away to have no apparent motion (in which case they would be hard for GAIA to use as a reference). Are there any extra-galactic sources (Quasars?) that could serve a similar function?

Did the Lightsquared interference really have no s (0)

Anonymous Coward | about 2 years ago | (#40565601)

Was there really no solution to the interference of Lightsquared's product with GPS devices?

Calibration (1)

Bob the Super Hamste (1152367) | about 2 years ago | (#40565735)

Why is it that we can't manually calibrate current GPS devices against known valid position data for better accuracy?

I have been to various benchmarks and have been able enter the correct altitude and it remains stable for a very shot time but am unable to correct for lat/lon differences.

Accessing DBs of transmitter locatiosn (1)

KhabaLox (1906148) | about 2 years ago | (#40565835)

Dr. Ramsey,
  In your post [slashdot.org] on Monday, you said:

A lot of the "this is not new" comments refer to differential positioning using reference receivers and having access to databases of transmitter locations (Rosum, the old Cursor positioning system from Cambridge Positioning Systems, etc). We consider those aspects to be undesirable constraints on a flexible opportunistic positioning system and don't rely on them.

Is the idea to be a fully self contained (and self teaching) system? Is there any way to (reliably) share transmitter location data between clients using some sort of P2P or swarm connection?

Compass and radar (1)

WaffleMonster (969671) | about 2 years ago | (#40565917)

Could your technology be augmented to enable bistatic radar apps for our mobile phones?

Have you considered doing the same using earths magnetic field rather than RF? Local varience within buildings or geology, earth field lines or using a RLG/GPS reference to see parallax in declination as a basis for rough positioning?

Handling Trust (1)

plover (150551) | about 2 years ago | (#40566101)

How do you see trust being handled in these systems? It would seem to beat the core of everything - anti-spoofing, error detection and correction, and possibly authorized receivers.

Multiple receivers for increased accuracy (1)

Bob the Super Hamste (1152367) | about 2 years ago | (#40566243)

Would it be possible to get a more accurate location data from GPS by using multiple receivers separated by some relatively close, aproximatly 1 meter, known distance and then averaging the returned position to get a more accurate center position?

I am envisioning something that uses 4 or 5 receives arranged in either a triangle or square with one receiver located in the center of the others. The distance between any 2 of the receivers would be at most slightly more than 1 meter which is below the accuracy of civilian GPS. From my past experience in using 2 handheld GPSes (one in each hand) it seems like this would be reasonable and would produce better results than using a single device.

Re:Multiple receivers for increased accuracy (1)

billybob_jcv (967047) | about 2 years ago | (#40567769)

That is done today. It is is called "Differential GPS" (DGPS) and "Real-Time Kinematics" (RTK). However, it's much more than just averaging - there are more complex mathematics involved to remove the errors common to both sets of measurements. RTK is done all the time in surveying and can achieve centimeter level accuracy in real-time. http://www.geod.nrcan.gc.ca/edu/rtk_e.php [nrcan.gc.ca]

Re:Multiple receivers for increased accuracy (1)

gnasher719 (869701) | about 2 years ago | (#40569425)

What the OP asked is not "Differential GPS"; actually it is the opposite.

We can assume that if you measure GPS coordinates at a given time and location, you will have a systematic error (inaccuracy in satellite position, different speed of radio signal due to weather) that is the same for all GPS receivers in an area, plus a random error different from GPS to GPS. Taking lots of measurements would tend to cancel out the random errors and leave you with the systematic error.

With differential GPS, you put one GPS at a known location, compare its known location with its measured location, and you get the systematic error + random error of that GPS. Then you take a second GPS at an unknown location, subtract the known error of the first GPS, and your second location is known with (twice random error).

Re:Multiple receivers for increased accuracy (1)

billybob_jcv (967047) | about 2 years ago | (#40571271)

RTK is often done based on a relative location from the base station. If a known monument is available, then the surveyor will usually set-up the base station over it, but if not, they often just use a landmark and do relative baselines.

Computers using Traditional Navigation? (3, Interesting)

bill_mcgonigle (4333) | about 2 years ago | (#40566389)

I found it striking that in the case of the drone that was forced down in Iran (e.g.) the 'return to base' failsafe seemed to be completely dependent on electronic signals.

It would seem much harder to spoof the position of the sun, the Earth's magnetic field, the position of the stars, etc. I presume, perhaps naively, that the sensors and algorithms to do this wouldn't be all that expensive or complex. What's the challenge in getting computers to use traditional navigation techniques?

Re:Computers using Traditional Navigation? (0)

Anonymous Coward | about 2 years ago | (#40573029)

>the sun
Mmm-hmmm, how are you going to distinguish the sun from any other source of equal intensity? Spectral analysis? LOL

>the Earth's magnetic field
Ever do the calibration of a digital compass? The earth's magnetic field is pissweak.

>position of the stars
A drone that doesn't work when it's cloudy or in broad daylight. Neat!

>I presume, perhaps naively, that the sensors and algorithms to do this wouldn't be all that expensive or complex
Let me put it this way: don't give up your day job.

Re:Computers using Traditional Navigation? (1)

DerekLyons (302214) | about 2 years ago | (#40574063)

What's the challenge in getting computers to use traditional navigation techniques?

There isn't a challenge - it's a well trodden path. The problem is that for the most part the sensors required are much more expensive than a GPS receiver, moderately complex, and require significant calibration and maintenance.

Pigeon Racing (1)

rockytopchip (1398125) | about 2 years ago | (#40566401)

What would you recommend for a real time low cost small size light weight position/speed sensor that could be used for the sport of racing homing pigeons? I'm not talking about a data logger, but a practical device that can transmit information to allow for remote real time information delivery.

How about receive selectivity? (0)

Anonymous Coward | about 2 years ago | (#40566727)

My question is rising off the ashes of the LightSquared fiasco. One key issue that LightSquared could not overcome is the reality of the receive side selectivity of existing GPS receivers. To my understanding, going forward, the FCC envisions to enforce stricter criteria for the receive side selectivity of new devices. Doesn't NAVSOP go in the exact opposite direction? It appears NAVSOP devices would work best with no receive side selectivity at all. Assuming NAVSOP proliferates, we would end up with a GPS vs. LightSquared situation on steroids, not only affecting L1, but essentially affecting the entire spectrum. Now if an effort like moving television off of 700Mhz and into digital broadcast, users of NAVSOP would feel the pressure and start pushing up against such re-banding efforts. Am I missing something? How would such a situation be avoided?

Feasibility in GPS-jammed world? (0)

Anonymous Coward | about 2 years ago | (#40567601)

If GPS is denied to US consumers and military (for whatever geopolitical reason), would NAVSOP itself be vulnerable to jamming? From your base description, could NAVSOP be defeated if a E&M source transmitted that wasn't in the "master database" of frequencies?

Solar Events? (1)

MrQuacker (1938262) | about 2 years ago | (#40568847)

How will the system function during/after a major solar event? Assuming a worst case scenario, satellites in orbit could be disabled for good. And depending on the severity, transmitters on earth may be affected as well.

Your thoughts?

Effect of world model choice on GPS (0)

Anonymous Coward | about 2 years ago | (#40569001)

It seems a lot of effort is going into bettering GPS accuracy by finding more triangulations (n-gations? :o) ) / reference signals. I was looking online at the WGD 84 earth model that the GPS system uses (http://en.wikipedia.org/wiki/World_Geodetic_System [wikipedia.com]) and read its accuracy was around +/- 1m. Since I often hear that GPS is accurate to about one meter (at least for the DoD), I wonder if this is why. That is, if we could get a more precise model (1cm? 1mm? LESS?), could we get that accuracy on our receivers, or is the error inherent in the GPS constellation/system itself? Thanks for your time.

Power requirements (0)

Anonymous Coward | about 2 years ago | (#40569717)

One key limitation with current GPS technology is the power requirements. Batteries in many handheld GPS units are drained in less than a day; 6-8 hours is an somewhat optimistic reality. What to expect from NAVSOP when it is available in a handheld form factor?

Best local navigation system (100mx100m)? (1)

Thagg (9904) | about 2 years ago | (#40570679)

I'd like to fly drones over a, say, 100x100 meter area with centimeter precision, possibly indoors, for filmmaking. GPS is clearly not going to work, even outdoors. Time Domain sells a system with 5 cm resolution, using UWB technology [timedomain.com] -- but is there anything better than that?

Bayesian tricks (1)

LeDopore (898286) | about 2 years ago | (#40571837)

Do you use Bayesian inference to combine positional information from many sources, some of which might be sorrily mistaken? I'd be interested in hearing more about the algorithms used to stitch this data together, and if there are any heuristics or approximations that help.

On the fly mapping with environmental data (1)

mattr (78516) | about 2 years ago | (#40574669)

You mentioned earlier the domination of signal strength when indoors. Can you also use patterns in observed environmental data for automated mapping and exploration?

For example a robot exploring a cave or a large indoor structure like a power plant might be able to even use information such as ambient temperature / humidity, echoic nature of surroundings, or patterns in ambient air pressure / acoustic input from machinery or the sound of treads against floor.

Also someone was skeptical about using stars to navigate in the day. However radio telescopes can make observations in the daytime, which seems to be the ultimate sensor for your platform. Would your system work to find landmarks underwater too?

Load More Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Sign up for Slashdot Newsletters
Create a Slashdot Account

Loading...