High Accuracy Indoor Location Tracking?

aletterman asks: "I am looking for technology that can allow my company to track the position of a fork lift as it moves around a warehouse. This would allow us to factor out one problem situation - where the lift was when the driver dropped off the product. Based on the width of our warehouse locations, we need a resolution of about +-1ft. Standard GPS can't get that accurate or work well indoors. The fork lifts already have a VT220 terminal running 802.11b, so adding another device would not be difficult. I am currently looking at a product that can triangulate via the RSSI of the 802.11b network, but I am concerned the changes in the product mix and density of the corrugated boxes will change the RSSI and introduce a mis-positioning of the locations. I would prefer that the device transmit a position either serially or via our 802.11b network. Our warehouses are fairly large (300,000+ sqft) and have a large of amount of corrugated boxes. Any suggestions are greatly appreciated!"

Grid

[orkysoft]

Paint a grid on the floor, with squares of 1 sq. ft., possibly with magnetic paint, and install cameras or magnetic sensors to sense the lines passing underneath. Add a compass or rotational sensor to help determine the orientation. Add some maths, stir, and you might just have something that might work. (Or not...)

Hockey Puck

[Glonoinha]

Look into the technology used by the NHL on Fox for making the hockey puck more visible to the home viewers.

Here [vistadevelopment.com] is an oversimplified diagram, but enough to get you pointed in the right direction.

Re:Grid

[TheWanderingHermit]

But with a lot of forklift traffic, people walking in and out, and boxes and crates that are picked up and put down (that will shift by small amounts when the forklift places or lifts them), and you'll find the paint gets worn away unevenly. After it's been on the floor for a year or so, it'll be hard to keep up with repainting the areas as they wear out.

Re:Grid

[prophetofdelphi]

What if the grid/barcodes/whatever were painted on the ceiling instead? Just place the sensors on the top of the forklift - just have to make sure they'd still be able to see whatever they're looking for at that distance (since the distance from the forklift to the ceiling is much greater than from the tires to the floor, obviously). This would prevent the grid/barcodes from wearing down at all.

Re:Grid

[delus10n0]

ILM (I think..) actually developed a camera rig system using something like that, for realtime combining of virtual spaces with what the camera is shooting. They used it on "A.I.", with random dots/barcodes/targets above the camera rig, passing by the actors (on a green screen).. another camera composited in the virtual world around the actors, and used the markers on the ceiling as a guide to where they were in the virtual space.

dead reckoning

[SpaceLifeForm]

Or deduced reckoning. Whichever you want to call it.

If you could the speed and direction information along with known beacons placed in the warehouse, you should be able to have the forklift know where it's positioned at all times.

Re:dead reckoning

[Glonoinha]

Is that anything like one guy shouting out 'Marco' and the fork lift driver shouting 'Polo!' ?

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:dead reckoning

[Que_Ball]

A ring laser gyro like this for aircraft cost in the neighborhood of $250,000.

A plane that wants to fly overseas routes like the atlantic routes to europe needs to have 2 of these.

I doubt that it's appropriate to adapt a device meant for objects traveling a high speeds over huge distance to something traveling in a small relative area at low speeds.

I think one of the floor grid suggestions might be workable. It reminds me of the old style optical mice that required the mirrored mouse pad with the grid l

Re:dead reckoning

[ACPosterChild]

Inertial location tracking has errors that add up quickly. They constantly need re-zeroed with something like GPS.

That particular system advertises 0.01G body acceleration detection. That's 3.86"/s/s (or 9.8cm/s/s). So, if you're not accelerating at at least 4" or 10cm per second it won't even register. Depending on the behavior of the driver, the system won't even know you're moving. Even in the best case, the system is limited to velocity intervals of +/- 4" or 10cm /s. So, for every X seconds of acceler

Re:dead reckoning

[77Punker]

Forklifts in warehouses can be difficult creatures. In the summer when I don't have school, I work at a place where sometimes I need to drive a forklift with flat, solid tires on a wet, greasy floor. It's a bit like ice skating at times, so determining the speed of the forklift could be quite difficult.

Encoders

[Doug Dante]

Place optical encoders on the left and right front or rear wheels of the fork lift, so that it knows its delta position based on dead reconning. (about 1mm resolution)

Add 'bar codes' that run the width of the major isles, and point optical encoders downward on the fork lift so that as it drives over them, it can 'reset' its position and eliminate any errors that build up while using dead reconing.

Try to place them so that the fork lift is expected to run over a bar code every 5-15 minutes or so (depends on errors that you measure in encoder accuracy, and the resolution that you need).

Hook them up to a PIC that kicks out the counters for dead reconing as well as any known location events via serial to your computer on which the 802.11b is located. An AVR butterfly will do the job.

Re:Encoders

[TheWanderingHermit]

You've got the (same problem [slashdot.org] as the first suggestion.

Any bar codes or anything else on the floor will wear out unevenly and after a few years, will require a constant cycle of painting to keep up with it.

Re:Encoders

[princessfuzzball]

What if the barcodes were set into the floor and covered with lexan??? Then you would not have to paint, and they would be accessable.

Re:Encoders

[Anonymous Coward]

Encoders are the way to go, but a slightly different way.

YOu need to measure wheel rotation with these encoders. This will give you distance traveled. And mount a gyroscope and integrate to give you absolute angle.

This method will work. Only one thing is, at certain positions, the thing will have to reset. For example, if the fork lift has a specific parking spot, have a reset button set the co-ordinates at that location to (0,0) or whatever.

Fork Lifts skid...

[malakai]

in most warehouses i've walked through there's often time product, grease, water, or any number of things on the floors. At times, the fork lift will slid through them in full brake. I've seen people play games with it it can become so slick (especially on polished concrete floors).

Re:Encoders

[Hast]

I have actually done something like this as an exercise as part of course in computer vision.

The point of that excerise what to use the fact that the distances between 4 points on a line has the same ratio independently of the location of the viewer. IIRC given points a, b, c, d then (b-a)/(d-c) will always be the same (it was a while since I looked at this and the math isn't my strong point anyways).

This was used in a system where goups of 4 marks were placed on the walls of room. A vehicle which moved i

"Tri"angulation doesn't have to be.

[NNKK]

I dunno if the product you're looking at can handle this, but in principle, just because three points of reference theoretically allows a perfect calculation doesn't mean you can't add more to provide greater resolution in an error-prone environment.

Let me know how this works out.

[AtariAmarok]

I STILL can't find my car keys.

iButton/RFID

[hool5400]

It's a bit more labor intensive, but i think it's the more sensible solution.

Each location (shelf/floor area) has a tag, RFID or iButton would both work i think. Each item/pallette has a similar tag. When dropping an item off he scans them both in with a mobile reader, uploaded to central, linking the two in a database.

Are you looking for the sexiest solution, or one that works?

Re:iButton/RFID

[PerspexAvenger]

Why keep the human in the loop?
Implant RFID-esque tags in the floor by the dropoff points, and install a reader loop on underside of the forklift.
If he really needs more accuracy between dropoffs, they could sprinkle a grid of the things at a 2ft spacing or somesuch.

Re:Infrared

[SteelLynx]

And it should be mentioned that the Ekahau Engine [ekahau.com] actually works quite well for indoor positioning based on 802.11 accesspoints.

A friend of mine is using it in his ph.d. project. Unfortunately, I don't have any links to the things he's done (don't think he has much online) so unfortunately I can't be more specific :-/

Re:Infrared

[zero_offset]

The page you linked says Ekahau has a 3.5' resolution.
The article is looking for something about three times as accurate.

Loads of Money....

[hughk]

I saw a lovely system at the Central Bank of Russia. Yes, really!

Money is stored in cassettes in a fully automatic warehouse. The actual warehouse uses an automatic system, (if you have seen a storage robot, it isn't a whole lot different). However money is shipped from the loading/unloading dock to the procssing stations and then from the processing stations to the warehouse loading/unloading station using robot forklifts.

The forklift control system was German, but I can't remember whose. They used a pulsed transmission system and used the arrival time for navigation. The main control computer knew where the forklifts were to the centimetre and gave them orders.

RFID

[Yonder Way]

Embed RFID tags in the floor. Put an RFID reader underneath the forklift. Have it report back over 802.11b with the RFID tag number(s) that it is closest to.

Re:RFID

[T-Ranger]

Thats what I was thinking.. Does the poster have to be within +/- 1', everywhere, or are there specific points of interest? If the later, just tag the points of interest.

If you find one...

[Mr. Sketch]

Let me know. I was looking for something similar for a cat locator project I was working on. This would plug into the cat locator [rentapi.com] portion of my website. My requirements are a little different since the locator module would have to be small enough to put around a cats neck.

So far, I have yet to see a solution presented in the comments that would work for my situation.

Re:If you find one...

[Scorchio]

My cat has developed a stealth mode. I'm sure he runs along on three legs, with the fourth paw over the bell.

you already bought a solution

[Anonymous Coward]

This would allow us to factor out one problem situation - where the lift was when the driver dropped off the product.

Why not ask the driver?

Triangulate On A Light

[TheWanderingHermit]

I know a lot of forklifts or other equipment sometimes have a flashing light on top. Could you do something similar, like have a bright light on top of the forklift (and if you have multiple forklifts, each could have a different color light), and have a few video cameras mounted on the ceiling. Every second or so a screencapture program could read a frame from each camera and scan it for the color of the light.

That might cause a problem with employees and their clothing, so you could even use two lights on a forklift, each a different color, so one lift is identified by red and green, or maybe several lights so it shows up as a large blob, bigger than any employee. You won't have to worry about echo or other problems that come from a radio signal in a large warehouse (which is probably made of metal).

Re:Triangulate On A Light

[TheWanderingHermit]

I was thinking about that, but I didn't want to go into tons of detail.

Cameras are dirt cheap now -- you can get USB cameras, and have a number of them tied into an old system (also mounted on a ceiling) that does nothing but forward their data over ethernet. Or you could use other cheap cameras that aren't usb -- there's options. With them being so cheap. you could mount a large number on the ceiling, so it would be easy to keep it in sight of a camera.

I don't trust floor sensors (things can fall on th

Cyberfork

[fm6]

The fork lifts already have a VT220 terminal running 802.11b, so adding another device would not be difficult.

So why on earth does a forklift have a terminal interface? The only reason I can think of is that the manufacturer was anticipating precisely the application you're trying to implement. Perhaps you should contact them.

Re:Cyberfork

[DAldredge]

So the person running the forklift would know where to place items and where to go for their next pickup.

Re:Cyberfork

[WinterSolstice]

We certainly use this sort of thing, combined with pallet scanning on the forklift. The operator can scan a pallet, work with it, and move on. Very fast, very accurate.

-WS

Computer Vision

[utahjazz]

Step 1) Put a big round ball on a stick on top of each forklift, each a different color. (perhaps even lit up with infra-red colors). Use some colors you don't have a lot of around.

Step 2) Put cameras around the area frequently taking stills, and using edge detection (with color filter masks) to locate balls in the camera's 2-D space.

Step 3) Read a book about computer vision and how you can recover the 3-D posotion of something, given it's 2-D position from multiple cameras (5 cameras per ball is best).

Re:Computer Vision

[Solder Fumes]

The only problem with this? Keeping me out of the warehouse, because they'd read two forklifts on my position!

Odometry and the EKF

[MankyD]

A little robotics might get you there. This may or may not be the best way, but it would work:

Careful odometry should get you within a foot or so, assuming you start from a known point. Yet, odometry coordinates inevitably degrade with time as errors build upon themselves.

There exists an algorithm, however, called the Extended Kalman Filter, that can help correct this. Using just a few sonar/iR sensors, corrections can be made to the coordinates.

Basically, as you move your forklift, its margin of error in position keeps increasing. Every once and awhile you fire off a handful of distance measurements from your sensors. Using the EKF, you can use this data along with a map of your warehouse to reduce your margin of error. The more measurements and the more accurate the readings, the closer you can properly position your forklift.

low tech

[Sevn]

Put cameras on the ceiling and paint big orange numbers on top of the forklifts.

Re:low tech

[unitron]

Since they've already got wireless terminals on the forklifts, why not paint the numbers on the ceiling and put a camera (pointed straight up) on top of each forklift? That way if you want to know where forklift number 47 is you don't have to visually search through a dozen or more camera feeds.

Barcodes

[Anonymous Coward]

I assume that a warehouse as large as yours already has a system for numbering all the shelves.

In that case, why don't you just attach barcodes to all shelves and add a barcode reader with a long coilable cord to the forklifts?

When making a drop, the driver would scan the boxes to be dropped, and then the location they were dropped. To make a pickup, he could scan the box to be picked up, and then a special "pick up" barcode on a label somewhere on the forklift.

Ideally with a system such as this, a user

Re:Barcodes

[Gordonjcp]

All the buses in the city where I live have a barcode sticker on the driver's window, with the registration number. As they drive in and out the depot, they are logged in and out. It works, and it works well.

smart dust

[XenonDif]

Check out a company called Dust Networks. They've been working on RFIDish localization for warehouse management based time of flight for years. I'm not sure if they've ever gotten it to work, but if anyone has it's these guys.

Otherwise, I think you're going to have to go with a bunch of cameras and some image processing. Maybe by taking pictures of the celing.

Cameras

[Quixote]

Here's an idea:
Paint a unique code on the roof of the forklift (something like a DataMatrix code or one of the other 2-D symbologies).

Put several cameras on the roof; fix them so they don't move; and calibrate them. You can probably use the WiFi cameras from Axis to not have to run cable.

Found it!

[Quixote]

I knew I'd seen a similar application somewhere.

This [att.com] is what you need: the "Bat Ultrasonic Location System", developed at ATT Cambridge labs (former).

From this page:

We have deployed the ultrasonic location system throughout our building, using 720 receivers to cover an area of around 1000m2 on three floors. The system can determine the positions of up to 75 objects each second, accurate to around 3cm in three dimensions.

BTW

[Andy Dodd]

This is basically how the Mattel Power Glove worked. The glove had 2 ultrasonic emitters on it, and then there was an array of 3 ultrasonic receivers that was placed on your TV.

The concept is similar to how GPS works, except that with ultrasound, your clocks don't need to be nearly as accurate and you can use MUCH lower frequencies.

Has been done before

[freshmkr]

Take heart---the problem you're contemplating has been fairly well studied.

I remember a professor here at CMU saying that you could do localization for forklifts by pointing a camera at the floor. Most warehouse floors have enough scratches and marks on them that as you wander around, you can get a pretty good idea of where you are by comparing them to a map (using techniques like Monte Carlo localization---google it!). Combined with encoders on the forklift wheels, you may be able to get the resolution you need.

Here is a paper describing technology like this [cmu.edu]. In the results they say they get accuracy down to a millimeter.

So, those talking about painting a grid on the floor have the right idea---but perhaps you don't even have to do that!

Re:Has been done before

[John Hasler]

> I remember a professor here at CMU saying that
> you could do localization for forklifts by
> pointing a camera at the floor.

You could use the guts of an optical mouse for that.

Re:Has been done before

[David Rolfe]

John: You could use the guts of an optical mouse for that.

No you couldn't.

Google "optical flow" and compare that to what this CMU research is about (digital object/pattern matching as applied to Monte Carlo localization).

These two techniques are WORLDS apart. Optical flow might not even be good enough to accurately measure location of a vehicle traveling in a straight line unless the surface contains no similarly aligned repeating elements or was specially patterned to allow for flow measurements across

Re:Has been done before

[StarsAreAlsoFire]

Yes -- the parent is probably a good option, especially if you can find all the software available for purchase.

Another alternative would be relative position device* such as a gyroscope based nav system like those used on commercial aircraft. These are certainly available commecially, and even if you only buy the hardware and write your own code you should have few problems.... just take care to avoid that divide by zero if you use eigen matrices to do the rotation sequences ;~)

If you really do get stuck

Differential GPS

[Anonymous Coward]

centimeter accuracy using indoor differential gps

http://www.gpsworld.com/gpsworld/article/articleDe tail.jsp?id=3086 [gpsworld.com]

Re:Differential GPS

[John Harrison]

Mod the parent up. I did a project at Stanford to create a mock-up GUI for a remote controlled helicopter to be used in search and rescue operations. This was in about 1997. The helicopter used differential GPS and got amazingly accurate position infomation, even while flying around at a good clip. This will give you much better accuracy than you need, assuming that the cardboard boxes don't mess with the signals too badly. What do you have in the boxes anyhow?

I think he needs products - not design ideas

[fluffy99]

I assume you want something somewhat off-the-shelf and not ideas for designing one from scratch. Here's a link to a company that specializes in this type of stuff and might be able to provide a ready to use product. http://www.visonictech.com/info_page.asp?info_id=4 16 [visonictech.com]

Re:I think he needs products - not design ideas

[robosmall]

I've implemented a couple of interesting wide area tracking systems in the past and have reasonable expertise on the various technologies involved.

RF solutions will not work indoors to the accuracies that you require (1ft). Too many problems with multi-path.

Vision-based solutions can be implemented, but robust commercial versions are expensive.

If you can dot the ceiling with paper targets and survey them, then use the new IS1200 from intersense (or contract them for a custom 2D version of their vision s

First part of any successfull solution

[SmallFurryCreature]

"I am looking for technology that can allow my company to track the position of a fork lift as it moves around a warehouse. This would allow us to factor out one problem situation - where the lift was when the driver dropped off the product . Based on the width of our warehouse locations, we need a resolution of about +-1ft. Standard GPS can't get that accurate or work well indoors. The fork lifts already have a VT220 terminal running 802.11b, so adding another device would not be difficult. I am currently looking at a product that can triangulate via the RSSI of the 802.11b network, but I am concerned the changes in the product mix and density of the corrugated boxes will change the RSSI and introduce a mis-positioning of the locations. I would prefer that the device transmit a position either serially or via our 802.11b network. Our warehouses are fairly large (300,000+ sqft) and have a large of amount of corrugated boxes. Any suggestions are greatly appreciated!"

If you just look at the highlighted words you first get the requirement "track position forklift warehouse" So he wants to know where the forklifts are in a warehouse. Okay. But WHY?

Second set of words is "where driver dropped product. Ah. I was wondering. Who gives a toss where the forklift is? Oh I worked in enough warehouses to know they are sometimes a pain to find if people don't return them or use them as a portable chair to take their break outside BUT it would be cheaper just to buy another one then set up a tracking system.

So we just got a case of a user making it not very clear what he wants. All of the answers so far have focused on trying to keep track of the forklift. Some intresting solutions and some stupid ones (measuring wheel spin on a forklift forgets that these things slip OFTEN).

However none of you have so far questioned why he wants to do this NOR wondered if this was indeed the real requirement.

More likely he wants to keep tracks of the goods. In practice goods are often misplaced in warehouses. If something is in the wrong rack it can be a pain to find it. Or worse you only notice it when the wrong thing is sent to the customer because items were mixed up.

IF this is the real problem, tracking goods, then all the given solutions are at best incomplete and at worst totally and utterly wrong to a degree that explains why so many it projects are overtime and overbudget.

But surely knowing the location of the forklift whill help tracking goods? Nope. Why? Because there is no way to track were an item was dropped by the forklift. Why not? What if the forklift operator drops of his pallet for a moment to shift another pallet out of his way? What if he takes the contents of a pallet off to put them on another pallet?

Basically this has to do with warehouse procedures that aren't followed or don't match the real situation. Ideally every storage place in a warehouse should have a unique identifier. Each storage place is catogorized as to what it can contain. Every item coming in FITS inside the storage place (not 1 item requiring two spaces OR 2 items going into the same space). At receiving the computer assigns an empty storage space. The forklift operator then takes the item to the required location and stores it. Ideally you want some kind of system to verify this BUT in real live all you need is good employees and good managers who allow each other to do their jobs.

If this system is followed then no goods will go missing. Problem is that this often doesn't happen. Neither does it seem to happen in the posters warehouse. If the forklift operators kept track off where they dropped items off OR dropped them off at the pre-assigned location then things wouldn't go missing.

Sadly he seems to go for a tech solution. Nice but it won't work unless he shifts his attention from the forklifts to the items. They are the ones missing in action.

For the most obvious failure and the sure sign that this p

Re:First part of any successfull solution

[duffbeer703]

The relevant point of your long-winded response is:

"Track the stuff, not the lift"

The problems with that solution are:

- There's alot of stuff
- It doesn't belong to the OP
- It stays in the warehouse for a brief period.

Tracking the forklift gives you all the info that you need, plus you get the added bonus of being able to figure out which employee isn't doing his job correctly.

Nope you got it wrong

[SmallFurryCreature]

Not unless you add to the specification. How do you know who is on what forklift and how do you know what that forklift is carrying. That is the reason you have to do it long-winded.

What you and others are perhaps comparing this with is truck tracking systems. BUT these systems are for a totally different need. They track trucks (and not what is in them) with gps because they already know what is in the truck from the loading bill AND because it helps them decide wich truck is closest to pick up an new fre

Re:First part of any successfull solution

[MrResistor]

Tracking the forklift gives you all the info that you need

No, tracking the forklift gives you all the information you need to find the forklift, and nothing more.

You might be able to make a good guess about where the goods are based on that information, but it's still a guess.

Tracking the position of the forklift does not tell you: Who's driving it; if it picks up or puts down a pallet, or if it's even carrying anything at all; what's on the pallet; if someone adds or removes items from a pallet, and

Re:First part of any successfull solution

[p7]

What you aren't taking into account is the info he didn't provide. The forklift has a VT220 terminal on it, what do you think they are doing with them? Surfing the web? My guess is the drivers log into them. Who's driving is solved. Maybe the driver some how logs when he drops something off, there goes loading, unloading and whether he has anything and all the other issues you mention. Personally using RFID tags, I could probably design a system that could do all that with no driver intervention. Jus

Re:First part of any successfull solution

[MrResistor]

What you aren't taking into account is the info he didn't provide.

What you aren't taking into account is what information he did provide: specifically that whatever their current system is, it isn't sufficient to prevent or find lost packages.

My guess is the drivers log into them. Who's driving is solved.

No, who's logged in is solved. Who's driving is a whole different question. Perhaps it hasn't occured to you that material handling isn't generally a field sought after by the highly literate?

Maybe

Re:First part of any successfull solution

[p7]

You are making alot of assumptions yourself. You assume that he doesn't know what is on the forklift. For all we know every item can be identified by the forklift automatically. They may be using a system like you describe. People can make mistakes and drop off an item in the wrong storage space, so they want this system to automatically verify that the driver was at the right storage container when he dropped off the item.

You may be right, but you go to far in assuming that he didn't provide enough in

Re:First part of any successfull solution

[MrResistor]

If he already knew that stuff, then the problem would already be solved. All he would have to do is extend his automatic item recognition to include locations, and from there it's a database problem.

The simple fact is that the position of the forklift is at best tertiary to the problem, and actually provides not a single bit of information relevant to finding packages. This much should be obvious to anyone who has ever done any kind of material handling.

SmallFurryCreature is right: aletterman is asking th

INU

[NitsujTPU]

Use an inertial navigation unit.

Some Idealab ideas...

[toybuilder]

These are two companies I've heard of from Idealab where I used to work:

Newbury Network's Location Server [newburynetworks.com] products uses 802.11b signal monitoring to do location detection. They offer a virtual docent system that uses the technology to allow the virtual docents to provide location-appropriate information.

Evolution Robotic's VSLAM [evolution.com] lets robots use odometry AND visual data to update its position information.

Depending on the size of the warehouse and the manner of "occlusion" that occurs, I'd say wiring up the warehouse with lots of cameras and triangulating to a beacon would be a pretty straightforward method... The hockey puck, indeed!

VSLAM

[toybuilder]

BTW, it's interesting to note that the VSLAM allows the robot to be "kidnapped" and dropped off at a new location...

If the robot is kidnapped at the beginning of exploration (right after the initial map is created), can it figure out its location? Or does the robot start exploration again?

The vSLAM algorithm contains a novel approach for data processing which enables quick detection and recovery from kidnapping scenarios. Though it's not advisable to kidnap the robot immediately before the landmark datab

Long antenna and ceiling mounted 802.11

[Corpus_Callosum]

Mount the 802.11 wireless access points on the ceiling of the factory and put a long vertically mounted antenna on the forklift (to minimize or eliminate the effects of floor geometry).

Then use triangulation software that allows you to train it and keep collecting data points until your target precision is hit.

RFID tags

[dshannon]

I implemented a similar system in a brewery warehouse about 12 years ago - we used ceiling mounted RF tags and a reader on the roof of the fork (with a 10-12 foot range), connected to the fork release/grab mechanism to match ceiling tag against location when the forkie picks up stock or puts it down - and there you go - he doesn't have to scan anything, but you know where that pallet is all the time. There are/were alternative solutions which involve mounting the reader under the body of the fork and buryi

Farming equipment

[citmanual]

I'm not sure if the resolution is tight enough for your needs, but this sort of problem is frequency used in large agri-businesses. Many of the larger operations use fixed position repeaters to increase the resolution of GPS and keep track of yields and soil conditions while planting, tilling, or harvesting.

Cricket Indoor Location System commercially avail

[metoc]

Check out the MIT Cricket Indoor Location System. http://cricket.csail.mit.edu/ [mit.edu].

It is commercially available from Crossbox Technologies http://www.xbow.com/Products/productsdetails.aspx? sid=116 [xbow.com]

LGVs and AGVs

[chrisatslashdot]

Ditch the driver and get yourself some Laser Guided Vehicles or Automated Guided Vehicles. These are in widespread use in industry and distribution in the US and Europe. If you go to the expense of tracking a forlift I can't help but believe that you could get a nice ROI by adding the hardware/software to replace the driver.

RFID

[mqx]

It sounds like a dirty word, but it's probably your solution: outfit your storage area with RFID, and put a sensor on the forklift so that when the forklift drops the item off, you can sense which RFID tag the forklift is close to.

The RFID tag may need to be in the floor, on the shelves, or whatever else: the beauty of this solution is that it's cheap: the tags are cheap and small and just need to be embedded around the floor: you then need to manually associate the tags with a location (shelf, etc).

What

Bet these guys would be willing to work with you

[grandpohbah]

Way better than 1ft resolution out of the box, but if you are serious, I bet they could dumb it down a bit.http://www.arcsecond.com/index.aspx [arcsecond.com]

found this

[zogger]

Seems to be sort of what you are looking for.

fiber optic gyro tracking stuff for warehouses [kvh.com]

Just ran across the release and remembered this past ask slashdot. Hope it's useful info.

ENSCO, Inc makes that

[srchestnut]

It's called Ranger, and uses radio to provide cm accuracy positions indoors or anywhere GPS isn't an option.
Check out the website:
http://www.ensco.com/products/homeland/rng/rng_ovr .htm [ensco.com]

There's contact information at the top.

Tachometers

[heroine]

Because of the number of obstructions, no sonic or propogation delay mechanism would work. No stationary cameras would work. Electromagnetic mechanisms would only be accurate to feet. You could put barcodes in random locations and get a camera on the vehicle to automatically detect the barcodes.

triangulate

[rkww]

Put a tall mast on the forklift and get two spools of fishing twine. Fasten the spools high on the walls in two adjacent corners and tie the twine to the mast. Measure how much twine is unspooled, and triangulate.

location system

[netmote]

Tracking moving assets like fork lifts is tricky. Specially when you want it down to a foot of accuracy. I've tried with a dead reckoning FOG gyro, indoor gps and rfid. The expensive FOG gyro drifts over time and needs often recalibration (every minute). The indoor GPS has issues with obstacles like walls and shelves. RFID simply only reaches a few inches of rf range. Wherenet.com has an interesting solution, but is very expensive. A better solution is using a mesh network with both RSSI and Ultrasoni