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Wireless Networking Hardware Science Technology

Forget GPS, Hello WPS 286

Posted by timothy
from the ded-reckoning dept.
No France writes "A company known as skyhook wireless has announced the commercial availability of its Wi-Fi Positioning System, or WPS. The company has compiled a database of every wireless access point it can find in a given city. When a mobile user running th Skyhook client is in a recorded area, their position is calculated by selecting the surrounding signals and comparing them to the reference database. Currently there are 25 US cities mapped, including New York City, Boston, Chicago, Los Angeles and San Francisco. Apparently this device is accurate to within 20-40 meters, though one has to wonder how well it deals with people moving their wireless access points."
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Forget GPS, Hello WPS

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  • Too Simple (Score:5, Funny)

    by nxtr (813179) on Tuesday June 21, 2005 @11:53PM (#12878442)
    They might as well give everybody a peice of paper with a huge X on it that says 'You are here'.
    • Skyhook? (Score:2, Interesting)

      by kingofalaska (885947)
      That is a mean trick played on newbies in the Army, at least in my first Air Assault unit. An old-timer says "go over to supply and get a skyhook, and some frequency grease for the antenna." He has a rational sounding explanation that the skyhook is the thing under the helo that the slings hook into. The newbie goes over to supply, and the seargent, playing along, sends him to someplace else. Everyone passes the poor newbie around, as long as the game can play.

      On a more serious note, this sounds suspicious

  • 20 - 40 meters? (Score:3, Insightful)

    by Anonymous Coward on Tuesday June 21, 2005 @11:54PM (#12878452)
    20 - 40 meters? Who will be forgetting GPS with that kind of crappy accuracy?
    • Why, when you young whippersnappers were still in diapers we were feeling lucky to get 100m accuracy with SA enabled.

      AND we had to walk uphill both ways in the snow to get it.
    • by Tony Hoyle (11698) <tmh@nodomain.org> on Wednesday June 22, 2005 @04:22AM (#12879221) Homepage
      Sounds optimistic...

      Let's say I'm within range of 50 access points all called 'Netgear'.

      Where am I?
      • Re:20 - 40 meters? (Score:2, Informative)

        by Anonymous Coward
        > Let's say I'm within range of 50 access points all called 'Netgear'.
        > Where am I?

        You do know that access points have MAC addresses, don't you? Every single MAC address is globally unique. They have a database of those, _not_ of the names.

        Note that this database is going to get stale quickly, as people turn on new APs, move existing ones, or upgrade broken ones. Still, I think it's a great thing to keep in your arsenal of positioning tools.
      • Let's say I'm within range of 50 access points all called 'Netgear'.

        Where am I?


        Utah?
  • by wintahmoot (17043) on Tuesday June 21, 2005 @11:55PM (#12878460) Homepage
    PlaceLab [placelab.org] has been doing this for a while, and it's free.
    • by Myself (57572) on Wednesday June 22, 2005 @12:38AM (#12878629) Journal
      Strange how the world turns, I just mentioned PlaceLab to a friend before loading Slashdot. Spooky!

      PlaceLab's big advantage is the ability to use multiple sources. Wardriving data is just one potential input. If you have a GPS receiver and a wi-fi card and a CDMA phone all connected, it'll use whichever is giving the most trustworthy results. So you can move smoothly between urban, rural, and indoor environments.

      What absolutely makes me giggle is this: "Morgan adds that GPS typically only locates things within a few hundred meters, whereas the Wi-Fi location system can get within 20 to 40 meters of an object."
      • by kormoc (122955)
        that's funny, mine typically is about 3 meters.

        see http://www.delorme.com/earthmatelt20/waas.asp [delorme.com]

        "it is possible where WAAS is available to experience accuracy of under three meters for the majority of tracking time."

        Mine has never been more then 10 meters off.
        • Same here... With WAAS on even in a city such as Boston my Garmin's accuracy is usually between 3 and 12 meters.

          What would be a cooler use for the wifi technology would be to have each of these access points have a small index on it in different categories. Thus you could have a category's such as "Coffee", "Food", "Sex workers", "Drugs" etc.

          Then if you choose "Coffee" it would say something like: "44th and 3rd: Starbucks: BAD!!! Keep Going!"

          To combat the problem of jokers just putting wrong crap out on
      • by suineg (647189) on Wednesday June 22, 2005 @01:15AM (#12878752)
        Well think about the fact that you pretty much need to be within 20 to 40 meters of an AP to even pick the signal up then it would make absolute sense.
    • by Anonymous Coward
      The paper worth reading here is: Cheng et al's "Accuracy Characterization for Metropolitan-scale Wi-Fi Localization" which explores the issues related to AP density, churn, positioning algorithm, etc. See: http://www.cs.ucsd.edu/groups/sysnet/miscpapers/mo bisys05p124.pdf [ucsd.edu]
    • by spiff42 (718678) <sdNO@SPAMsymlink.dk> on Wednesday June 22, 2005 @03:55AM (#12879158) Homepage
      I have been working with a commercial localization system called Ehahau Positioning Engine [ekahau.com] which we have acquired a license for at the Technical University of Denmark. This system uses the signal strengths of available access points to determine the position. The client is a piece of software running either on a laptop or PDA (they also have some nifty tags that can be used).

      The client software running on the tracked device measures the signal strength of the access points, forwards the data to the server which calculates the position. The big-brother scenario is avoided as long as you still have to install the client yourself.

      The major drawback of the system is that it needs extensive calibration, since they are using not only the available access points, but also the signal strength of these. Normally they suggest calibration in a 5x5m (15x15ft) grid. More calibration points yield a more accurate result.

      And now the piece of information you have all been waiting for: accuracy. With a good calibration this can yield accuracies of arround 1m. In my tests (indoor) the accuracies fluctuate a bit, but is at least better than 3m 95% of the time.

      Just as the system described in the original post, Ekahau requires no extra hardware (we already have 2-300 APs on campus).

      /Spiff

  • by nemostultae (524156) on Tuesday June 21, 2005 @11:57PM (#12878466) Homepage
    Apparently this device is accurate to within 20-40 meters

    Hell, I can guess where I am to that accuracy. I thought GPSs where accurate within 5-8 meters nowadays. And this sounds really useful out in the open ocean, you know, where all those rouge wireless access points hang out.
    • And this sounds really useful out in the open ocean, you know, where all those rouge wireless access points hang out.

      Ah, yes, the pink ones.
    • Re:What a joke... (Score:5, Informative)

      by Bogwood (855051) on Wednesday June 22, 2005 @02:19AM (#12878932)
      But vanilla GPS just isn't accurate in urban canyons. In London's docklands area (high buildings) GPS gives accuracy in the 200 to 400m region due to multipath effects. As well as obscuring satellites, tall buildings cause reflections of GPS signals which can cause large errors in the pseudo-range calculations making accurate position reporting very difficult. Places like NYC or Chicago are useless for GPS.

      I would imagine that supplementing GPS with other position determining mechanisms (like WiFi) could be beneficial in these circumstances.
  • 20 to 40 meters of accuracy? I work with various grades of GPS and even with low accuracy gps I can get within 10 feet no problem. I mapped wireless access points before and they really turn out to be VERY inaccurate overall.

    Oh well maybe some fun could be had, like PHYSICAL address spoofing.
    • 20 to 40 meters of accuracy? I work with various grades of GPS and even with low accuracy gps I can get within 10 feet no problem.

      My FAVORITE kind of slashdot post to respond to is this one. It's a combination of "I'm missing the point entirely" AND "I think I'm a lot smarter than I am." All rolled up into four little sentences.

      WHY IS WPS USEFUL: Because there are a lot of urban areas where you can't get GPS signals for shit. Try New York City, for one--you're lucky if you can get two or three satell
      • I don't know about you, but I've been using my Garmin ique 3600 in NYC (Manhattan) with relatively good results. True, there are times when I lose the fix and there are times when multipath errors degrade performance, but these are exceptions rather than the rule. Usually, moving up or down a block fixes it. This scenario is ideally suited to the use of an inertial system in combination with GPS (which my Garmin doesn't have but more modern auto navigation systems do).

        On the other hand, the technology in
  • by photon317 (208409) on Tuesday June 21, 2005 @11:59PM (#12878480)

    Rather than trying to maintain a static database of AP locations and signal strengths, they should just put some live wifi nodes out there with real GPS on them and track the AP map in realtime as it shifts. Or they could give free service to a select small percentage of customers in return for attaching a GPS device and helping recalibrate the map with some background software once a month or something.
  • Forget GPS

    Weeeeeee! This mean we can nuke the GPS stationary satellites now? ''Shut 'em down guys!''
    • It's probably not well known, but there have been effectively "GPS stationary satellites" in operation in major cities for quite a long time called WAAS. Basically WAAS (or Wide Area Augmentation System) has about 25 stationary ground system that correct for GPS signals with a signal that's compatible with GPS broadcasts. Originally designed by the FAA, it's really helpful for GPS car navigation systems...

      Read more at this site [garmin.com]...

      Sometimes reality is better than you know... ;^)

      • WAAS is not "stationary satellites". There is such a thing, called a pseudolite, but that's not WAAS.

        The ground stations generate the corrections, but these are sent to stationary satellites in geosynchronous orbit. A WAAS capable GPS receiver can receive those signals in addition to the GPS signals with a compatible GPS receiver. This information is in the linked article.

        It's actually pretty useless for car navigation systems, but good for marketing. Since SA was turned down, the WAAS signals only are
  • I honestly would expect it to be even worse.
    If this determines position by signal strength wouldn't it then be dependent on the type of antenna you were using with your WiFi card? Sometimes my signal moves around even in the same position or drops significantly lower in "dead spots". What if I'm using one of those crazy Pringles can antennas?

    "Hey! 100% signal here, I'm here, over there and...yep, that a ways too!"

    Anyhow, what an awesome idea, I mean, it's not like we have anything like this in exist
  • though one has to wonder how well it deals with people moving their wireless access points.

    And thats exactly what it will not catch on. No company in their right mind would make products that counted on devices that aren't guarenteed to not be moved. Although it might work if the WiFi APs received GPS data and then acted as base stations to enhance the resolution of your GPS device. What I'd really like to see if GPS that worked in buildings and underground.
    • Well, first of all, there is no shortage of companies that are not in their right mind...

      Secondly, this may be very useful for uhm, uhh, well, I dunno...
  • Interesting. . . . (Score:5, Insightful)

    by Bagheera (71311) on Wednesday June 22, 2005 @12:22AM (#12878575) Homepage Journal
    . . . but I suspect ultimately of little practical value. Having done quite a bit of RF scanning on the WiFi bands in one of their listed cities (San Francisco) I've seen first hand how signals behave in that dense urban environment.

    GPS and WAAS operate on time signals and highly accurate positioning. Cell towers would be inherently more accurate since thier positions are accurately known and don't change (except under very unusual circumstances.

    WiFi nodes come up and down constantly, and their position is rarely going to be accurately known by anyone but the person who installed it - and chances are they're not telling "you" exactly where the node is.

    Given "walk around surveying" to map the nodes, it's not really a surprise they have accuracy that's no better than an early 2 channel GPS receiver.

    And, as others have pointed out, if I'm in downtown San Francisco (or any other city) I don't need my GPS to tell me I'm at 5th and Townsend. For directions there's Mapquest, Google, Yahoo Maps, etc...

    Interesting technology. But it sounds more like something a hobbiest would come up with than business.

    • In addition, cell tower broadcasts are done with timing requirements nearly as stringent as those used by the GPS system. (In fact, most cell towers have a GPS receiver in them for the sole purpose of providing a time reference.) As a result it's possible to get a semi-decent position fix from cell towers without even relying on signal strength. Combine this with a few GPS signals and you get Augmented GPS, aka E911.

      WiFi APs don't even come close to such timing accuracy.
      • by Dufffader (164439)
        But for typical outdoor GPS usage, depending on AGPS (Augmented GPS/Assisted GPS, etc) is a little redundant. You might as well stick to pure GPS for navigation.

        What gets interesting is that AGPS is supposed to provide positioning indoors too, or in areas where GPS don't work so well. In a densely urban areas (think downtown NYC), acquiring the minimum 3 satellites for triangulation is not so easy. This is where using CellIDs and timing information from cellphone infrastructure to get your position is usef
  • 20-40 meters? (Score:5, Interesting)

    by Jurisenpai (261790) on Wednesday June 22, 2005 @12:25AM (#12878586) Homepage
    Don't these people realize how accurate GPS positioning has become?

    MGIS-grade equipment [trimble.com] can now give positions with sub-foot ( 30cm) postprocessed accuracy. Survey-grade equipment can get within 5-10 cm.

    As neat as WPS sounds, I don't think that anyone will be giving up GPS soon if WPS can't get any more accurate than 20-40 meters.
    • As neat as WPS sounds, I don't think that anyone will be giving up GPS soon if WPS can't get any more accurate than 20-40 meters.
      That was my first thought. 20-40 metres isn't even good enough for street navigation. What is it good for, telling you which wireless cafe you're sitting in?
    • Actually survey-grade equipment can give real-time positions within about 1cm via RTK GPS.
      • Point taken, but RTK equipment is insanely expensive and out of the price range of most small surveying companies (that my company deals with, anyway).
    • Re:20-40 meters? (Score:3, Interesting)

      by Bastian (66383)
      Yeah, but most GPS equipment of that grade falls into the "If you have to ask how much it costs, you can't afford it" price range.

      The system I work with can do sub-meter, sub centimeter with post-process. It retails for ~$40,000 plus a couple thou for a DGPS subscription and a few hundred to a couple thou for the DMI (odometer) equipment. And its precision falls off sharply (to as bad as 5 meters) in metropolitan areas where you get the GPS signal getting blocked by and bouncing off of tall buildings.

      My
      • Re:20-40 meters? (Score:3, Informative)

        by Jurisenpai (261790)
        I'm not sure what kind of system you're working with (or how old), but the system I linked to above is *very* roughly $3500. The software would add another $1500. So for about $5000, you have submeter accuracy. Multipath is still a problem, yes, but there have been great advances in solving that, too.

        GPS has come down in price incredibly in the last few years. You don't even need a subscription to a DGPS service anymore.
    • I wish there were an open source DGPS project out there.

      The premise seems simple enough: Have one GPS at a fixed position, and the other receives corrections via radio.

      But I haven't been able to find anything.

      My house sits on a large lot (over an acre) and I've wanted to survey it fairly accurately (within a foot at least) to recreate it digitally and be able to plan shops, gardens, landscaping, etc.

      • I imagine that there's no open-source DGPS software because equipment that can receive a DGPS signal already has the firmware for decoding it built in. Why bother?

        If what you're talking about is free DGPS service, that does exist, but only in certain localities. UW-Madison has set up several beacons and differential transmitters around Madison, WI, and they are free for anyone to use. I believe that the Ohio Department of Transportation has done a similar thing for the entire state, but I'm not sure if t
        • What I'm talking about is using 2 separate GPS units, each connected to a linux box.

          The fixed unit is on a known, surveyed point.

          The other unit is out and about taking measurements. The fixed unit sends the mobile unit real-time data corrections.

          Commercial DGPS equipment works in much the same way, but is very, very expensive.

          Perhaps it's not possible to do what I'm thinking using a couple of old linux boxes, a couple off the shelf GPS's, and a means of communication (wi-fi, bluetooth, UHF / VHF radio
          • I hadn't looked into this for a while, and it looks like some work has been done on it.

            Several open source programs / projects are listed here [edu-observatory.org].

            I haven't tried whether they work the way I want them to, or whether they provide the accuracy I crave... :}

    • Re:20-40 meters? (Score:2, Insightful)

      by invisigoth (131518)
      This can solve some problems associated with standard GPS. Namely, that satellite-based GPS systems fail when structures block line-of-sight to the satellites in the sky. This can include things like tall buildings in urban areas, or underground parking garages, etc. Since WPS is purely terrestrial, it can overcome many of these problems. Of course, satellite-based GPS is still preferable if you don't have these issues.
    • Re:20-40 meters? (Score:2, Insightful)

      by wramsdel (463149)
      What accuracy, exactly, does GPS give you when it can't see any satellites? Skyhook isn't trying to sell this as a replacement for GPS, rather as a complementary technology. In fact, they even have a nice USA Today-style graph on their "Technology" page showing that the overlap between GPS and WPS is fairly small. What marketing person in the world would look at this graph and say "Let's position our technology as a replacement for GPS!". That's not even Internet-bubble thinking.

      That being said, keep i
      • Skyhook isn't trying to sell this as a replacement for GPS, rather as a complementary technology. In fact, they even have a nice USA Today-style graph on their "Technology" page showing that the overlap between GPS and WPS is fairly small. What marketing person in the world would look at this graph and say "Let's position our technology as a replacement for GPS!". That's not even Internet-bubble thinking.

        The impression given by this story is that Skyhook are looking to compete directly with GPS. If t

  • Useless? (Score:2, Funny)

    by knightPhlight (173012)
    I'm currently surrounded by the SSIDs, "linksys" and "default". Can someone tell me where I am?
  • 20-40 meters? try to navigate on that.

    Not to mention the tons of other problems such as access points moving and disappearing and the inharently weak signal makes wps less reliable under minor amounts of interference.

    it's a neat trick for someone who has nothing better to do but with as advanced as gps is and the ability to track via cellphone I don't see this having any real market.
  • by SnprBoB86 (576143) on Wednesday June 22, 2005 @01:07AM (#12878730) Homepage
    20-40 ft? This is totally useless for street navigation, surveying, etc.

    What this is useful for is grander scale positioning without the need for a GPS device built into a portable device.

    For example, timezones are far larger than 20-40ft. Laptops could be configured to automatically adjust the timezone setting to match the closest access points, no GPS device needed. A weather monitor utility could always automatically show the local weather. A star map could be configured to show the local sky. I'm sure many people can think of others.
    • A weather monitor utility could always automatically show the local weather.

      What's up with everybody talking about weather applications all the time? You guys don't have windows or something?

    • For example, timezones are far larger than 20-40ft. Laptops could be configured to automatically adjust the timezone setting to match the closest access points

      Timezones are not that easily derived from position, you would need a quite large and fairly uptodate database of timezone borders for that.

      And your favorite OS may not support timezone changes without restarting the system...
  • The article states:

    The way it works is that the company has compiled a database of every wireless access point in a given a city. It did this by having people literally drive the streets "listening" for 802.11 signals. Using the unique identifier of the wireless router, it notes in the database where the access point is located.

    Is that unique identifier such as SSID or access point MAC address (is that even accessible to a client)? Since a large number of people would check "Do not broadcast the SSID"

    • Since a large number of people would check "Do not broadcast the SSID" following their manufacturer's manual on security,

      What manual says to do this? Turning off SSID broadcast is *not* a security measure in any sense, at all.

      For one thing, the SSID is included in every single packet that the access point sends out. Period. So getting it is easy with or without the SSID broadcast.

      For another thing, turning off SSID doesn't prevent anybody from connecting to the network. It will prevent stupider displays
  • From the article:
    Morgan adds that GPS typically only locates things within a few hundred meters

    Huh? I can get down to 6 meters and in AUS we don't have WAAS. This is just FUD.

    And what happens if they move a wireless access point?

    There are lots of applications that could do with indoors coverage, but this isn't a GPS killer.

    I could see something like this being a complementary addition to a GPS. GPS+WPS or somethink like that. But the power of GPS is the ability to locate yourself anywhere on the plane
  • 1) The recent press release by Atmel and u-blox announcing indoor capable GPS http://www.u-blox.com/news/SuperCS.html [u-blox.com]

    2) Better coverage area

    3) Not reliant on the masses to provide APs and keep them in a consistent spot

    4) GPS probably functions better in a blackout

    5) Don't need a laptop (Not sure if WPS requires one)

    And to finish off the list, I'm sure if you just scan the rest of the comments you will find 5 more.

    Interesting idea, but it doesn't seem like a good bet when there is already a good solut
  • I did a lot of research on this topic for my sensor networks class and we came to the conclusion that it would be highly inaccurate.
  • Now I think we can compile a WiFi hotspot map and lookup the nearest one rather than rely on those stupid faded chalk marks. If only they'd carry the SSID as well ..

    Btw, we've already been there and done positioning using local RF stuff.

    I had this app that used a MIDP form to draw the way you moved. It used to go crazy when I was in the lift - but on the horizontal it used to work nicely. I couldn't release it because it uses a few undocumented Ericsson OPA APIs. It used to obtain timing advances of all n
  • Put a GPS and a laptop in the boot of a taxi. It collects updates, and every time it finds an unprotected AP, it uploads the data to a central database. Client computers could do the same thing for downloading. Parasitic navigation! Wonder if this would be legal?
  • Please notice the G in GPS ! The system is global and really works everywhere outside the buildings. And "everywhere" actually means outside your city and even outside USA!
    Can u imagine?!
  • How would one get lost in a dense city? Street signs are everywhere and dense fog won't make orienting much more difficult. There are always people whom you can ask. GPS is useful in areas without population: open sea, deserts, Lappland, Alaska. The use case for such a device is pretty much zero.
  • The US is getting more and more paranoid. I wouldn't be surprised if it is routinely shutdown every time we are in a homeland security declared red alert.
    Nice to have a alternative.

    Also, most new laptops have WiFi these days - not GPS.
    That alone make this useful.
  • What about RPS? (Score:4, Interesting)

    by scorp1us (235526) on Wednesday June 22, 2005 @09:28AM (#12880207) Journal
    Can't you triangulate from FM radio station signal strength?

    It woud have the following advangates:
    Way smaller database
    Way more coverage

    It should be easy to do with the adevnt of software radio.

    The only down side, is that you wouldn't need this company anymore!

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