Ask Slashdot: Image Recognition For Race Timing?

First time accepted submitter int2str writes "Autocross is a form of motorsports practiced in the U.S. and around the world where car enthusiasts explore the capabilities of their car in an open parking lot or similar suited area. It's point-to-point racing (not closed circuit). Most of these events are organized by car clubs and volunteers. Timing is usually done with a form of detection beam at start and finish that gets interrupted by the car crossing the beam. Many commercial systems are available. All of these system require the operator to enter the car's number or ID and requires the cars finishing in the order they started. So if one car is not able to finish, the operator has to intervene, or timing is broken. For closed circuit racing, transponder systems are available to address this problem. But such systems require sensor loops in the track or overhead (bridge setup) and the transponders are expensive. Do you think it would be possible to design a timing system using off-the-shelf parts and open source solutions to uniquely distinguish about 100 participating vehicles and time them from a start to a finish point, independently of their finishing order?" Read below for some more details: int2str continues: "My initial idea would be:

• Use (web-?)cameras at each end that feed into a Linux based notebook (USB/Ethernet).
• Start recoding still images as fast as possible when motion is detected
• Identify unique shape, numbers, barcode, qr code or similar in the images, that have been attached using a magnet to the vehicle's door.

Difficulties to overcome:

• Camera with high enough shutter speed to get recognizable image of vehicle traveling 30-60mph
• Quickly and accurately identify a unique symbol or shape

So far I've started looking into OpenCV as a possible tool for image recognition, but have not been able to find a capture solution. Does anybody have experience with something like this? The solution would be open source and well documented as to benefit the many car clubs around the country and the world."

Comments

Seems simple

[pspahn]

• Timer on board vehicle
• Timer starts as it leaves starting line
• Timer stops as it crosses finish line
• Timer info is sent to controller

What exactly is the problem here?

Re:Seems simple

[TubeSteak]

What exactly is the problem here?

The problem is that your solution requires us to trust the client.
Not only should you never trust the client, you should assume the client is hostile and act accordingly.

Re:Seems simple

[Yaur]

RFID, maybe with a camera as backup, seems like the way to go.

Re:Seems simple

[xtal]

Detecting the finish line is one problem.

Detecting multiple cars crossing the finish line within a few ms is another problem.

Trusting the client is another issue.

Price is another..

Re:Seems simple

[SomePgmr]

Much (if not most) of kart, rc car and auto racing is timed using transponders (either active or passive) and a buried loop (antenna) at the start/finish. All crossings are time stamped by hardware there, and read into a db for race management and results. This method is also commonly used for marathons and such.

It makes for one authority on time, where multiple racers would have times relative to each other regardless of the accuracy of actual time at the device... which is set using buttons on the device, GPS, locally attached computer or with NTP.

Perhaps there's something unique about motocross that doesn't lend itself to the same systems everyone else uses... but otherwise, you nailed it.

Re:Seems simple

[JoeMerchant]

Autocross generally charges $20ish as an entry fee... the timer onboard vehicle would raise the barrier to entry higher than most clubs would want (due to cost / complexity for newcomers.)

Re:Seems simple

[Reelin]

you should assume the client is hostile and act accordingly

And this line of reasoning is how Trusted Computing was born. Wait, you mean we're supposed to trust the client unless we have a good reason not to?!?

Re:Seems simple

[fluffy99]

RFID, maybe with a camera as backup, seems like the way to go.

It certainly works for bike and running races. Last few races I attended had antenna beside the course and not a timing mat. Perhaps combining the RFID for the ID and a photosensor for more accurate timing.

Or for more low tech, a person at the start and finish keying in the numbers. Plenty of running races have hand held timers that the official just clicks the button (maybe trigger with photosensor instead) and keys the race tag number.

Re:Seems simple

[fluffy99]

Detecting multiple cars crossing the finish line within a few ms is another problem.

Autocross usually doesn't have multiple cars that close to each other. They are staged and sent on the track at intervals. Sometimes as the poster pointed out, they will pass each other and finish "out-of-order" which confuses a timing system that assumes FIFO/LILO.

Re:Seems simple

[tlhIngan]

The problem is that your solution requires us to trust the client.
Not only should you never trust the client, you should assume the client is hostile and act accordingly.

So put timer inside a box with serially numbered seals. Timers are issued at start of event and must be returned at end. If seal has been tampered, vehicle it was tracking is disqualified.

If necessary, issue them on start line and collect them at finish line. Have simple loops at start and finish line to automatically start and stop timer. A simple Arduino board should be good for this. Make it so the seals must be opened in order to extract timing data, reset the board, then re-seal timer. Include in timing data number of times it was started and stopped, too, or if it was attempted to be started while already running, or stopped while already stopped.

Re:Seems simple

[pmontra]

Agreed, but it works in bicycle racing, and people race in bunches and teams there. Never heard of anybody tampering with the transponders. Your cars should arrive alone and if the transponder doesn't match the car you disqualify it.

Re:Seems simple

[6Yankee]

Seals seemed to work well enough when I was hanging around gliders. I distinctly remember someone going for a height achievement, and the barograph (old-school, pen on paper drum) being started and wrapped in tape, which was then signed across the joins by several witnesses. The barograph was completely inaccessible in flight anyway, but the simple ideas are often the best.

I don't recall any such precautions for the (film) cameras they used to photograph waypoints on distance attempts, but I suppose it would be significantly harder to fake. With a digital camera, maybe sealing the card slot would be a good idea, but even then you're going to have to get above all the checkpoints somehow, or collude with someone who already has.

Of course, this was all five years before I'd even seen a GPS unit (and that one weighed more than the barograph did), so I've got now idea how it's done now. :)

Re:Seems simple

[Gription]

Not Motorcross... Autocross.
Over 90% of the participants are using the car in their driveway. There will be no "buried loop (antenna)" because you don't modify a parking lot you borrowed for a day. People are not going to use a $200 HotLap timer when they are just there to drive fast.

Auto-X is a very, very entry level motor sport. Most people don't even have their own helmet so they borrow a loaner that most clubs have available. The system HAS to be external to the car. There isn't any question about this.
Say you want to see who can go around a little course faster in your wife's Volvo wagon. That is Auto-X. How much modification are you going to do to your wife's wagon before you and your friends take turns driving through cones? None.
If you don't understand this then be clear about this: You don't understand.

RFID stickers and barcodes are a really interesting idea. You would still want to do the timing with a photo sensor but having the secondary system to tag the photo sensor events to the correct car would solve lots of things like people walking through the lights and messing up all the times for people who are on course. Barcode is the easiest and cheapest to generate but I see the issue there being that the barcode would need to be at a consistent height for the sensor to read it. Cars aren't consistent so you wouldn't be able to do that without a sophisticated machine vision system.

This type of upgrade to a timing system would make running an event a lot more fun. The timing system is the source of lots of cussing from workers and participants. A timing system generally costs a bit more then a grand so I doubt you would be able to develop something for less then that. I see this as something that might be added to a current system either by the manufacturer or as a personal upgrade. If you were able to come up with an open source type of solution or upgrade you would be a hero to car clubs across the country.

Re:Seems simple

[bitingduck]

Agreed, but it works in bicycle racing, and people race in bunches and teams there. Never heard of anybody tampering with the transponders. Your cars should arrive alone and if the transponder doesn't match the car you disqualify it.

It doesn't work all that well in bicycle racing-- if you're using chips, you still need a good camera at the finish, and if you have a good camera at the finish you don't need chips. Chips are a convenience for picking order in the middle/back of the pack, but aren't good for picking close finishes. I've never seen any published data on the spatial resolution of the chip systems (and asked the sales people directly because they were trying to sell it to me). The demos I've seen for track racing (I did a lot of track promoting for 6 years) were unimpressive to say the least-- they really offered me nothing that couldn't be done for a lot less with a tape system. And for the money that a chip system costs ($12-15K) you can get a finishlynx and some timing tapes that give you what you need with no ambiguity in photo finishes. I also know more than a few cases in stage races and CX where the officials with watches and pads of paper had the results finished and posted before the chip people were even close to unwinding their results.

Chip systems would work well for Autocross (the big market for MyLaps seems to be automotive, and they look decent for that) but are $$$, which I suspect is why the OP submitted in the first place. For the OP, it might be possible to do something reasonable with a miniDV camera reading race numbers (large black on white) combined with either one of the commercial systems for a few hundred $ or something homemade with arduinos and photosensors or timing tapes, and then roll your own software to combine the two data sets.

Re:Seems simple

[SomePgmr]

That makes sense. And while these systems are affordable in nearly any kind of racing, I can see where it might be too much for the wife's volvo.

Your typical rfid system just isn't going to work. Barcode is problematic at best. You're almost better off with soap on a window.

Re:Seems simple

[SomePgmr]

Actually, just had a thought. While rfid and barcode+camera probably won't work well, if you only have a couple racers at a time, you could probably use inexpensive active transmitters and a stationary receiver next to the s/f.

The way the big kids' loops work is taking a whole bunch of readings at the loop, not just one. Then the decoder averages all the readings per transmitter at the loop from first hit to last, generates a median crossing time, time stamps it against the received ID and stores it. This gets rid of the "well my transponder is higher powered than that guys" issues. The only downside is you have go past the finish line.

You could probably combine this with a beam trip (also cheap) to get reasonably accurate crossing times. If you're correlating the two, you also have ID's. Whole rig would be portable and definitely come in under $1k, but would involve making hardware. Just a thought.

simplify

[TheSHAD0W]

Some large numbers on the sides or hood of the car would make image recognition, if not trivial, at least relatively simple.

Re:simplify

[JoeMerchant]

Numbers on the cars are more or less standard, but are usually a mixture of different types, including shoe polish on the windows - OCR would be... challenging.

Re:simplify

[SmurfButcher Bob]

Well then, just offload the problem into The Cloud!

Done!

Most definitely

[Antisyzygy]

I worked in Face Recognition as a research assistant for my MS. I was part of a group designing a robust end-to-end system for the purposes of identifying people in a wide variety of conditions. This problem seems easier because you can assume that the cars will be in one location within one time frame, the camera is fixed and everything in your data set will cross this line unless they break down, they will have almost identical 3D structure (unlike the face), and you can expect some identifying marks on the front end that crosses the finish line. As long as you have some sort of identifying marks, you can use standard face/object recognition techniques to identify the vehicle. There are some pretty advanced algorithms out there. The best out there when I was actively working in face recognition was STASM and Pittpatt. Better yet, if you had some unique identifier expected at some part of the vehicle, you can easily make the problem much easier. For example, have each one use an infrared identification tag located in precisely the same spot relative to the build of the vehicle.

Re:Most definitely

[Antisyzygy]

I suspect what you mean is that I am a demon because I sided with Teh 3vil |31g |3r0th3r. Technology != evil. Its how its applied that matters. There are legitimate uses for such technology, such as identifying a person who is trying to enter their home, or a person who is trying to access their bank account, or even to identify a person known to make bombs and blow people up who try to board airplanes. Its not necessary to be a luddite to avoid abuses of technology. Fix the system rather than oppress scientific development and innovation. You can band together with like minded people and force laws into existence that protect you from abuse, or you can just stop being apathetic and never allow such abusive laws to pass.

Re:Most definitely

[JoeMerchant]

they will have almost identical 3D structure (unlike the face), and you can expect some identifying marks on the front end that crosses the finish line. As long as you have some sort of identifying marks, you can use standard face/object recognition techniques to identify the vehicle.

The cars in autocross are as (and usually more) varied as what you see on the street. In a field of 100 competitors, you might expect to see 5 or 6 participants with a particular make/model, for the most popular (e.g. 6 Miatas, 5 Neons, 4 Corvettes, 4 Mustangs, and a hodge podge of all kinds of cars from the last 40 years.)

Re:Most definitely

[Antisyzygy]

This is still more-or-less a significant domain reduction over the human face. If you weren't human you wouldn't be able to identify one face from another. Try identifying faces upside-down sometime in a split second. We are uniquely built to identify very small variations in the human face in upright position. I suspect the front end of a car would be much less difficult. For example, first classify what the make of the car is, then classify color, then classify markings. If you have a database of cars in the race you will find a match with high probability.

Re:Most definitely

[JoeMerchant]

There is a practical issue with photographing the front (hard to protect the camera) - most timing equipment is located 30' to the side of the finish line (you can get closer at the start.)

Re:Most definitely

[St.Creed]

I must remember that insult - it's quite good :)

Re:Most definitely

[Fnord666]

I must remember that insult - it's quite good :)

Too bad you can't credit it properly since whomever it was is a wuss and posted anonymously.

QR Codes

[insane]

Put giant QR code stickers on the hood/doors. Done.

Barcodes

[GrahamCox]

How about sticking a big barcode to the competition number panel and use a simple barcode scanner to ID the vehicle as the beam breaker is triggered?

Re:Barcodes

[Dan East]

This is the cheapest / most versatile option, but you would use QR codes or other 2D codes designed specifically for this kind of image scanning and not traditional 1D "barcodes". Issues to consider would be lighting, the camera's ability to capture clear images at whatever speed the vehicle is moving at, etc.

Re:Barcodes

[GrahamCox]

Using QR Codes is still complicated compared to simple barcodes. You need a fast camera, image processing, etc. That might be acceptable of course. But a simple laser barcode scanner is cheap and effective, and simpler to interface. You can print the barcode for the competitor on a sheet of office paper and stick it to a side window with tape. Super-cheap and likely to work. There could be a problem ensuring that several vehicles arriving at once were able to be scanned (that may not be an issue for the sport, if vehicles are set off at timed intervals and don't tend to catch one another - not sure).

Re:Barcodes

[Anonymous Coward]

I disagree that 2D barcodes are better for this than 1D - the OP said they only need to distinguish between ~100 vehicles, so you really don't need high data density. Plus, I think using a 1D code could help you get around the shutter-speed issue: if you turn the barcode so the stripes are horizontal and capture images across the start/finish lines, motion blur shouldn't affect your image capture. You would need to make sure you get the barcodes on each car positioned at the same height (relative to your cameras), and that the lighting is good enough (high contrast is the most important factor). Note that this system wouldn't work if you have cars finishing at the same time (but then, I don't see how the beam-blocking systems would figure out if two different cars are finishing at the same time).

I suggest looking into zbar (zbar.sourceforge.net). It's an open source barcode reading software, which has support for many different types of 1D and 2D codes. It comes with two example programs - one for static images, and one for webcams. I've never tried the webcam version, but the static image decoder works great.

For generating barcodes, check out:
http://code.google.com/p/postscriptbarcode/
There's a web-based front end for it, but with a little hacking on the Postscript version you can print out pretty much any kind of barcode in any format you want.

Re:Barcodes

[white_owl]

I think Barcodes are a good idea, and as the grandparent of this comment mentions they could be on a fixed part of the car say the front right corner of the car. Magnetic signs would be reusable, although a white sheet of paper with blue tape holding it on would make it easy to find the barcode in an image. Then when the car trips a light beam at the start/finish line you can take one frame and the barcode will be approximately in the same location. I would argue in favor of 2d codes vs QR codes. If you use 2D barcodes so that the lines are horizontal, then the system could tolerate a fair amount of blur. Since you only need an identifying number for the car the ability of QR codes to code a good deal of data is not needed.

Re:Barcodes

[CityZen]

Yes, you win. Note the two main ideas: 1) Use the existing beam breakers to get the timing down to whatever precision is needed.
2) Have the beam breaker also trigger the camera or whatever system is recording the bar code or other easily-machine-identifiable visual code.
The camera part doesn't need to be timing critical, in this setup, since the beam breaker system is dealing with that.
Of course, there's still the matter of writing a bit of software to tie everything together, but that should be pretty elementary.
(If you don't have an existing beam breaker timer system, then you could probably find something at instructables.com.)

RFID

[Anonymous Coward]

There is already an outfit doing motorcycle road racing using RFID. it would work in this instance as well.

Re:RFID

[GameboyRMH]

I was going to suggest this. The stage rallies around here use optically triggered timing plus RFID for identification.

The autocross group is on an even smaller budget so we use a guy with a stopwatch and a clipboard. It's good enough.

You're overcomplicating it

[Uksi]

I autocross and I've been thinking about the same problem. I even thought about writing my own free software and building plans for off-the-shelf/cheap-to-make transponders ($1200 for a wireless transmitter unit? jesus).

The problem is that if a car doesn't finish and misses the timing mark--the software shoudl just let you to fix it up. You should be able to say "this car didn't finish" (has a missing tick) or "ignore this tick" (some corner worker tripped the lights accidentally). Then it shoudl be able to just recalculate the times affected. It seems so simple to me, I am baffled that it hasn't been implemented.

All the cars starts in the same order, all the numbers are known at hte start time and cars never pass each other. So you have always same-sequence travel of cars. All you need to do is fix occassional lacks of ticks or extra ticks. No need to re-run the cars.

Re:You're overcomplicating it

[JoeMerchant]

I also autocross, and I think a practical solution would be to add a network camera to each electric eye installation, connect them wired or wireless to a notebook, and simply snap photos as the beam is broken. Keep timestamp records for each beam break event, assume everything is running normally, but also do a fairly simple color check on the car to verify that the assumed finish time event matches the start event. Display a series of thumbnails on the screen for each automatically determined start/finish pair, and if the system ever messes up, all the operator has to do is slide the finish photos to match the start photos - and the times will be calculated automatically (iPad would make a nice interface for the system...)

If you want to be lazy enough for the system to i.d. the cars exactly for you (and tabulate all the times with minimal operator intervention), I'd go to issuing QR (2D bar) code panels and add that to the software - but it will still fault occasionally and need human attention, and the other thing to consider is if fiddling with the bar codes is really less work than just babysitting the timer and hand entering the car numbers as they start.

Re:You're overcomplicating it

[Jumperalex]

Except for reruns, double driver cars, novices (or experts) who are late / get into the wrong grid slot. You can't assume the order is always the same.

Re:You're overcomplicating it

[Zadaz]

A thousand times this.

Your problem doesn't need complicated (and expensive) things like transponders, infrared identifiers or image recognition cameras. You're dealing with edge cases that a human can deal with in a few seconds if they have the right interface for it.

Give them the right interface for it.

Re:You're overcomplicating it

[Uksi]

It doesn't, because at that point, the car that spun is considered a "DNF." The car that spun can be instructed to not to trip the timing lights and if they do, it can be fixed.

In autocross, cars are not allowed to pas each other. If someone spins and the car behind gets too close (within 10 seconds), it gets red-flagged and gets a re-run.

Re:You're overcomplicating it

[Uksi]

The starter always confirms the starting car's number at the starting line. So if someone gets into the wrong grid spot, it doesn't matter because their car number would be still correct at the starting line. If someone is driving someone else's car and doesn't inform timing appropriateyl, then you would have that problem anyway.

Reruns are not an issue because they are just like regular runs, except done again for a special reason. Cars still line up at the starting line in a certain order to run a re-run.

Double-driver cars are not an issue with sequencing--with any other solution, the club needs to know which driver is at the starting line.

The order that's the same is the order of cars that have been launched from the starting line, not the order of cars lining up for that line.

Re:You're overcomplicating it

[Jumperalex]

ahh I see what you are saying. "All the cars starts in the same order" was not clear and made it sound like you meant for the entire heat they are always in the same order. Perhaps, "all the cars cross the finish line in the same order they started" would have been easier for me to understand.

Re:You're overcomplicating it

[bitingduck]

shutter speed doesn't have to match frame rate for video cameras-- Many MiniDV cameras are capable of 1/2000 s shutter speeds, even when they're only shooting 30 fps. So you can get a quite clear picture of someone moving pretty fast-- we use 1/1000 for bike races where the finishes are ~60-70 kph and can quite easily read 12 cm high numbers off riders who are 7 m from the camera, and that's with an SD camera and 4:3 format. For road races I know people who use an HD camera with widescreen format to cover the whole road more easily. From other posts it sounds like autocrossers typically finish at less than 100 kph, so it's probably very doable with a MiniDV camera.

Use the best software

[jbeaupre]

I'd suggest using the best software available: the human brain.

Version 1
Aim a camera at the finish line. Aimed to capture the racer's number and any other identifying information. Set the camera to be triggered by the interruption of an IR beam. Place a clock in the picture field.
During / after the race, find each racer's picture and record the time.

Version 2
Aim a video camera at the finish line.
Use a laser pointer as a finish line. Aim it at something white and make sure it is visible as a racer crosses
Put a clock in the field.
After the race, fast forward and write down the time each racer crossed.

As a bonus, you have photo evidence in case there is any dispute.

Re:Use the best software

[swalve]

I was going to suggest the same sort of thing. Two cameras in timesync with each other.

Re:Use the best software

[WebMasterP]

This won't work. Almost all forms of autocross guarantee a driver 3 runs (each driver does one run, then each driver does a second set, etc.). Knowing what time you have to beat after each run is a huge part of autocross. The data has to be input in real time, or at least close so that results can be viewed after each run. This problem gets worse with ProSolo, where there are two courses and challenges require results for a class to figure "handicap times". Additionally, multiple cars are on course at one time (generally like 3), so it's very difficult for one person to do.

In my region, we have some open source custom software that a local member wrote that works pretty good and automatically inputs the times as they come in. I've modified the software to make entering our timing cards faster, but we're a bluetooth bar code reader and some business cars away from having a very streamlined process.

The other thing the author of the original question is missing out is how penalties for hitting cones or missing gates is entered. There has to be some human interaction there. If my region didn't have timing cards, we trusted the computer and the operator completely, we could have 1 person running timing, instead of 2 (I'm not counting the announcer or course control). National level SCCA autocross handles this problem by having someone with a bar code scanner standing near the start line that scans a bar code on your helmet as you drive up.

Re:Use the best software

[Jumperalex]

Racers want to know their time when they cross the line or very soon after, not after their heat / event. The system needs to be reasonably realtime.

Similar cars

[LoudMusic]

What happens if two dudes show up in a blue Miata?

Re:Similar cars

[BoberFett]

Even worse, what happens when two dudes show up in a Delorean and finish the race before they even start?

Re:Similar cars

[Anonymous Coward]

Then they are probably a nice couple

Re:Similar cars

[Anonymous Coward]

Why would they start the race if they've already finished it?

Re:Similar cars

[JoeMerchant]

Heard in the Paddock Why are you Spec Miata drivers so aggressive? "We are compensating for our ChickCars."

Re:Similar cars

[pmontra]

Of course. Both cars and neutrinos can speed into tunnels between Switzerland and Italy so there must be a way.

Re:Similar cars

[Eristone]

Yes we can -- they're Brown neutrinos

Use AprilTags to identify vehicles

[Anonymous Coward]

They're similar to QR codes but optimized for the needs of robotics (similar to your needs).

In robotics, the main need is for robust recognition, and accuracy.

QR codes are much more complicated because they need a lot more "payload" bytes (millions of unique codes), whereas you only need to distinguish between a couple hundred codes

there is even source code available:
http://april.eecs.umich.edu/wiki/index.php/April_Tags

Not quite that easy...

[Anonymous Coward]

I have run timing & scoring for track events (I don't AutoX), but you are under-estimating the problem. Time tolerances for a winning finish can be as close as .0001 seconds. Any variation in the delay for a camera or the time needed to process the image could be a serious problem. Another problem would be car placement, cars will not always cross the line in a nice, neat manner.

Those problems can have real monetary consequences when you factor in the product contingencies (free race tires and other products) that are commonly provided by manufacturers to winning amateur motor sports and AutoX participants. Not to mention the possible impact on season long points races for championships.

Timing loops and lights are very accurate, with loops easily meeting the .0001 second requirement we adhere to. I have personally seen time attack contests decided by a .0003 second margin of victory. Price for loop systems is more than the light based systems, but I have enough experience with the loop systems to know they are very accurate when set up correctly.

If you do want to go home-brew, your best bet might be to mix cameras with timing lights. Get the timing from the lights and let the camera based system assign the the light's times to each specific car assuming you can get the recognition working correctly.

Re:Not quite that easy...

[flatulus]

Timing tolerances of +/- 100 microseconds?

At 100 miles/hr (160 km/hr) that would be a distance of 0.176 inches (4.44mm).

I think you meant "milliseconds" which is 0.001, not 0.0001. Still, multiply the above by ten and you get:

1.76 inches or 44.4 mm

That's a pretty awesome "photo finish."

And for that matter, what about relativistic effects?

Re:Not quite that easy...

[geezer nerd]

These are interesting numbers, and yes, I verified them with my own calculator.

But it has been stated here that the race is fastest time over a fixed course, not a nose-nose competition between multiple vehicles. That makes the short difference of distance not very relevant.

AForge Rocks

[Anonymous Coward]

AForge has the components you need to compliment a IR system: motion tracking and object identification. I've used it on a similar project for a cup team to get corner exit ride heights and yaw. Camera shutter speed shouldn't be much of an issue with just about any off the shelf camera. Camera position will require a bit of testing but that will be pretty obvious. Using video as an alternative with an off the shelf camera is another matter. Here frame rates rule. Even if you jump through the hoops to get 60 FPS you would only have captured the start and stop times with .016 of a second.

outsource everything!

[pinfall]

Automaticallt take your pics and upload to dropbox, pay mechanical turks to identify and enter data, profit!

Bluetooth?

[crow]

How quickly can Bluetooth establish a connection? Use the optical beams to determine the time that a car passes a point, and give each driver a Bluetooth headset that has been paired with laptops used to record the timing.

You can test the range to make sure it will work--you should only need a few meters. You can get cheap headsets for somewhere around $50, probably less.

I have no idea if this would actually work, but it should be possible to do a test run with parts you probably already have.

Re:Bluetooth?

[JoeMerchant]

Bluetooth isn't the right tech, you're looking for RFID in this case.

Re:Bluetooth?

[crow]

Yes, RFID would be better, but something like Bluetooth or even turning on WiFi on a cell phone in the car could be sufficient, and it could eliminate the need to purchase equipment that isn't already on-hand. It also has a nice hack spirit if it works, in using something in ways beyond what it was designed for.

Forget autocross, how about foot races?

[Radical Moderate]

As a race organizer, timing chips are a PIA, it would be awesome if facial recognition could track everyone at the start and finish. We're talking up to 10,000 people though, and you'd have to have a photo on file to identify each person. The finish would be easy, everyone is spread out, but at the start you have a lot of faces crossing the starting line simultaneously. Aside from being kind of creepy, is it workable?

Re:Forget autocross, how about foot races?

[blair1q]

Why are timing chips a PIA?

What's the error rate?

Re:Forget autocross, how about foot races?

[Radical Moderate]

User error....trying to get everyone to turn them in, paying for lost chips, etc. Not a pain for the runners, but a big pain for organizers.

GPS?

[flatulus]

I know this has a scalability problem (i.e. the cost of equipment goes up linearly with the number of contestants) but you could build a self-contained GPS device that tracks a car's position throughout the event. Have it record position information to flash as often as possible (Sparkfun has a GPS receiver that will update position 10 times/sec for US $61). At the end of the event, everyone turns in their GPS device and their position recordings are uploaded into a computer.

Now one may argue that GPS position error could be enough to make the winner ambiguous (i.e. "photo finish"). But position errors due to RF propagation are "systemic", in that they would affect all receivers in the same vicinity pretty much equally. Further, with a large number of position samples and high update rate, post-processing could be done to calculate trajectory of the possible winners as they approach the finish line. It simply isn't possible to accelerate or decelerate so quickly that you can't interpolate position and velocity in the vicinity of the finish line.

For the "systemic position errors", a single reference GPS receiver at a stationary location next to the finish line can be used to determine position "wander" due to RF, ephemeris, selective availability (even though it's off these days) and use this to subtract out this systemic error from everyones' position data.

Would be fun to build :-)

Re:GPS?

[Antisyzygy]

http://ask.slashdot.org/comments.pl?sid=2499210&cid=37875118 There are image processing techniques that would work with relatively small identification marks and a sufficiently "good enough" camera. The processing may take 5 minutes but you can cut to commercial and have a human verify it later. The issue is getting the original system accurate enough you are 99 percent sure whoever crossed the line first, crossed it. Facial recognition systems already have this level of accuracy. Just like voting systems however, for fairness you need human review before passing definite judgement. Apply some science and you would have a killer product there. Im surprised there aren't more industries employing at least one academic to make their systems more cutting edge.

Re:GPS?

[JoeMerchant]

See traqmate.com

Re:GPS?

[Jumperalex]

but too expensive to give to every driver and since newbies can walk on the day of the event the club would also need a good number of "loaner" units. Much like they do with loaner helmets.

Re:GPS?

[cojsl]

Current optical timing systems for autocross time to the thousandth of a second- and there are dead heats even then. So GPS is no where near accurate enough.

Factoid- prior to national events two parallel timing systems are set up and tested against each other to ensure consistent results. IIRC, anything greater than 5 thousands variation between them calls a timing system into question.

RFID

[Anonymous Coward]

Don't know if it would work in auto sports but sounds like a use for RFID, http://en.wikipedia.org/wiki/Radio-frequency_identification#Race_timing

Practical experience with autox T&S systems

[cojsl]

I'm an autocrosser with experience setting up, maintaining, and troubleshooting both an older T&S system, and the new system used by the SCCA at national events. Ours was the first local region to install the new "national" system, so I'm familiar with the "issues" surrounding the current T&S options.

There are several practical issues with optical systems for automated vehicle recognition- number and class markings are already tough to get consistent without requiring an additional barcode or QR large enough (some competitors would gripe about a huge barcode) to be useful at the 30'+ distance finish line sensors are set back to minimize getting hit by spinning cars. Add in the fact that existing markings some times fall off on course, or competitors in dual driver cars forget to change numbers between runs, and it's tough to be certain you'd have something consistent to try to recognize.

The national T&S system uses a wireless barcode reader operated by a worker in the starting queue to read stickers placed on competitors helmets to register cars in the T&S software. Locally, we position the T&S trailer to allow the operators to manually enter vehicles as they enter the start queue. Human eyes really are the most flexible here "shouldn't 80ES be 180ES?".

I like one of the comments above about a webcam triggered by the finish light taking a picture with a clock display in it. Unless there was OCR to immediately post the result to the software, the results feedback would be too slow for our region- we have real time announcement of finish stats, and the software can post results to a web server real time for smartphone access in paddock. The T&S software uploads a small file to the web server in the 20ish second gap between finishing cars.

Apologies for not offering solutions, but hopefully the extra info about some of the issues can help shape a solution.

Re:Practical experience with autox T&S systems

[JoeMerchant]

The national T&S system uses a wireless barcode reader operated by a worker in the starting queue to read stickers placed on competitors helmets to register cars in the T&S software.

At my local events, there are usually a few people sharing loaner helmets...

Use the open source Predator Tracking

[wmaiouiru]

This is pretty much a tracking problem, I would use the open source Predator Tracking algorithm to track each of the car simultaneously. The problem I see is if it is going to be fast enough for 100 cars, but it is worth to investigate it. http://info.ee.surrey.ac.uk/Personal/Z.Kalal/ Alternatively, thinking about using open source-hardware as a solution, use the open source Arduino Micro-controller Piece the sensor you need, and you will have your system at a much lower price ! http://www.arduino.cc/

Re:Use the open source Predator Tracking

[JoeMerchant]

Don't know if Predator refers to the military UAV, but it got me thinking, float a camera on a balloon and video the whole track from above....

RFID?

[ssyladin]

Why not put an RFID tracker on each car? They're relatively cheap and you can store some encrypted identifier in it. Pillar or mat sensors would pick up when the car crosses the line, though it might be a challenge finding sensors that'd pick up a car at 60mph...

Selective Wavelength Emission/Absorption

[cosm]

Special paint that reflects/absorbs only at certain frequencies. You have a 'stickers' that go on all four corners of the vehicle. The finish line has a spread-spectrum laser array blasting across it. When a car crosses the line, each car is tagged with unique tape. The laser light reflected will be unique to the vehicle. You triangulate the reflected lights timings and use that in conjunction with the wavelength reflected back and you've got a car and you've got a time.

Unique tape on each car. Cheap, replaceable. Not a perfect solution, but some variant of this involving selected emission/absorption is a winning ticket. I made this up in 1 minute and have no idea if there are any preexisting solutions that do this. For the pedants; yes tape could peel off and yes people could cheat some how I'm sure, blah blah blah, and I'm sure there is a more optimal solution blah blah blah, and I'm sure you'll have issues in X Y Z situation with A B C conditions blah blah blah. Go make something better and sell it.

Autocross or footraces, just use existing tech

[rust627]

An Australian security company has developed and is selling to petrol stations and some other businesses a number plate recognition program that is capable (I have seen it in operation) of reading and identifying car number plates with reasonable (98% +) accuracy at a distance of about 50 Metres (Maybe more, but the one I saw was working at that distance) on cars driving on a normal suburban road (speed limit 60 Kmh).
With larger numbers such as the display numbers on a race car, or the vest on a foot racer I don't think it would have any difficulty. And for the racers who 'forget' to change their numbers across multiple vehicles, well I am sure that they could live with their personal results being posted a little later after someone had checked the image generated as they crossed the line.
In some events at the club level in rallying you are disqualified if you are not showing your numbers for the various judges and officials to easily identify you during the race (much as that goes against the general slashdot desire for privacy and anonymity at all times)

Yep - if you can do the lifting

[Mr. Underbridge]

There has been a lot of work for recognizing images in video. Here, if you're smart you should be able to do the recognition given a single still, which means it's just ordinary image processing after extraction from the video.

Make it easier on yourself by making the numbers something like bright yellow on blue with a white border (for instance). Then just look for segments of each image with high response for yellow and blue. Then extract the video and pass it through an OCR tool.

Also, put the camera somewhere like the apex of a turn where they have to slow down and you'll be perpendicular to the side of the car (with enough distance that your camera rig doesn't get creamed).

Great idea but addressing issue of latency?

[w0mprat]

Accuracy hard to achieve. You'd have to carefully track the latency between the webcams image and the software timestamping the video data. Not an easy coding excercise, and would require calibration with accurate timing equipment. This latency also better be stable. I don't know too much about using linux for realtime work but I have heard it has some latency issues at the kernel level that causes trouble for audio pro's.

If you want to do this with a web cam and a bit of code on a linux machine, well 30fps video gets you a lower bound of 33ms time resolution. That's before the camera feeds to the USB data channel, then any gamer will tell you USB has some latency, and then software has to process the image data. High powered laptop and a good camera might be able to do all this as low as 100ms before it can timestamp the data. Image processing for identifying the vehicle can then happen at any time. This would need to be carefully accounted for in deciding who wins a race.

Proper race timing needs to be 3 decimal places, at 200kph (124mph) a 1/1000th of a second ammounts to 6cm of difference. Races are really won and lost on as little as this and often the timing is done even finer.

Re:Great idea but addressing issue of latency?

[Bob9113]

Proper race timing needs to be 3 decimal places, at 200kph (124mph) a 1/1000th of a second ammounts to 6cm of difference.

Good math.

AutoX is much slower than that. This may not work for F1, but F1 can afford the fancy equipment.

AutoX top speed is well below 100kph on most tracks, and you can put a turn near the finish line to keep the speed across the line under 50 kph (I suspect the turn near the finish is pretty common anyway, to keep the course exit speed down). It's also rarely more important than who buys the first round at the bar afterwards, so you could probably go as low as the hundredth with no loss. 1/4th the speed, 1/10th the resolution gets you to 2.4 meters. You should be able to hit that 99% of the time with one crappy camera. Better gear for a better answer, or use multiple cameras and average the answer.

Am I missing something?

[cob666]

First, I'm not familiar with car racing so apologies if my observation is idiotic.

The problem I see with having bar codes or RFID measure the time is how the car crosses the finish line. Because the OP mentioned a beam being interrupted I imagine the finish is determined by the front of the car touching the finish line (not unlike any other type of racing) so if the time is measured by a barcode or image on the roof or door then how do you match that with the front of the vehicle. Also, if the time is measured by when a sensor picks up an RFID tag then again you have issues with mat / receiver sensitivity and tolerances in the transponder triggering the sensor.

Because only one car is on the track at a time you do have some wiggle room, I'm sure there would be many ways to accomplish this but it seems like you're already doing what would seem like the 'best' approach:
System where both IR beams are hooked up the same time, beam 1 starts the time, beam 2 stops the timer. Before each car, race official 'initialized' the timer system by entering information about the car racing, this would solve two issues, the first is that it would reset the timer back to zero, the other being that if the previous car didn't cross the finish beam to stop the timer, the initialize process would automagically flag the previous car as not finishing (not sure how that would effect the time for that driver though). You could also put in other beams throughout the course that would give you times up to that point in the race. So, if you have a start beam, mid course beam and finish line beam, the start beam would start the time, the mid course beam would just grab the time but keep the timer going, the finish line beam would stop the timer.

Is this feasible, too simplistic or am I overlooking something important?

Re:Am I missing something?

[cojsl]

Not idiotic at all, you made good inferences. The current popular systems have an optical beam transceiver and reflector pair at both the start and finish lines, which are hard wired to a fairly simple timing box with multiple time displays that can track 2 or more (typically 4) times simultaneously (which also limits how many vehicles can be on course at once), with the oldest time being replaced by the newest time, so timing integrity is not dependent on the PC, but on the "simpler" hardware inside the timing box. As events are timed to the thousandth of a second- with "dead heats" occurring even then, depending on a PC for timing accuracy is not the best choice. At our events, one of the T&S staff's job is "manual time log"- writing every new time down direct from the timer box, along with the vehicle or event causing the trip- tumbleweeds, false trips by workers, rain, snow (which happened this year), etc, to generate an independent audit trail of results. The timing box sends new times to a PC running the T&S software via a serial connection. The T&S software operators enter cars in the start queue into the software, make adjustments for wrong/ missing numbers, false trips, extra trips, etc in real time. Cars are sent onto course approx. every 30 seconds for a safety margin, with runs lasting from 30-70 seconds depending on the size of the course. On a large course, 3-4 cars is about the max on course at a time.

two cameras?

[ai4px]

Two cameras? One camera that the cars drive over or under and a 2nd camera perpendicular looking at the side of the same car. Place a barcode on the front of the car... shutter speed would not be so much of an issue as the car would approach the camera for a relatively long period of time. The second camera marks when the car crosses the finish line.

Do not complicate the problem

[Anonymous Coward]

I say have you heard of the Boston marathon or near any popular marathon. They attach a RFID chip to the sneaker and record when it crosses the start and at the end. They collect the start and stop of thousands of people on the same day and crossing in large groups out of order.

There is also open source license plate recognition.
You could have every driver use a fingerprint reader and part of the start and finish is the drivers running to/from the car.

Similar, for RC

[Spiked_Three]

I have been working on a racing timing system for RC; https://picasaweb.google.com/104667803940601062545/Spiked3#5624165831383052962 is an older screenshot, but you get the idea. In my research I came across this; https://sites.google.com/site/easylapcounter/home which does recognize based on imagery. Your idea certainly seems feasible. for RC, we just byte the bullet and use the expensive MyLaps (AMB) transponder system ($3000 base + $125 per transponder). I assume they have some huge patent on it because it seems like it would easy and cheap to copy, yet no one has done it. Good luck.

This cannot be hard

[NEDHead]

I think my cell phone can do this already

Magnetic stickers, eh?

[jafo]

The problem with magnetic stickers is... Corvettes have fiberglass body panels. :-)

I once ran timing, here are my thoughts:

Personally, I don't think that transponders are expensive, and I think they'd be a great solution which would absolutely fail because of politics. "You mean I have to buy a $100 device (or rent for $5/event) to mount to my $40,000 car that has $2,000 rims and $1,400 tires?!? What do you think I am, made of money?!?"

I suspect you won't be able to do good detection except if the cars stop at the end. That's something you'll have to play with though, maybe you can set up a zone past the end where they have to stop to get recognized, or *MAYBE* the camera can deal with them if they stick to the recommended speed off the track. Cameras are very bad at getting sharp shots of sideways motion though. It'll also depend on the conditions out.

I imagine you will need to use a hardware timing device that runs in real-time and then you can pull the time off in the non-realtime OS. That or you'll need to run real-time OS extensions. Maybe you can get something reasonable out of a hardware interrupt like a serial/parallel port line change. The normal x86 Linux clock is 1ms resolution, and plenty of jitter, so just expecting to use the clock under Linux is probably unrealistic.

These people are as serious as a heart attack about this hobby. Saying "Accurate to within a few thou is probably good enough" is a good way to see exactly how good your insurance plan is. :-)

You're going to have to deal with things like a car leaving the starting line with "185" on it's side and crossing the finish with "85", "18", or even "1 5" on it. :-)

The "Predator" OpenCV system sounds like it would be awesome to try in this situation.

Consider setting up a place where the cars can go to get recognized and their number entered, maybe at the starting line, but maybe a dedicated area. Predator/OpenCV may be able to detect things like the letter that fell off during the run, but it may also mis-detect in some cases. You'll probably need someone eye-balling the start and finish anyway.

Good luck with that. I tried writing up some documentation for how to run the system I at our Autocross after they trained me on it, and I had my ass handed to me...

Re:Magnetic stickers, eh?

[Sez Zero]

Personally, I don't think that transponders are expensive, and I think they'd be a great solution which would absolutely fail because of politics. "You mean I have to buy a $100 device (or rent for $5/event) to mount to my $40,000 car that has $2,000 rims and $1,400 tires?!? What do you think I am, made of money?!?"

Having been on the other side as an organizer, I can tell you that it is usually pretty easy to extort a few more dollars from someone at the event. Here's how the conversation goes:

Org: So, I see you don't have your RainBow License for this event?
Racer: No, I wasn't sure I needed one for today
Org: You need one if you want to race
Racer: Well, I don't have one. What do I need to do?
Org: You need to go see Bob in Rainbows and give him $50
Racer: Aw, man, $50?!?!
Org: Yup.
Racer: I'm not paying that
Org: So you mean you're going to just head home after preparing your car for the last several weekend, spending hundreds of dollars on tires and other expenses, driving several hours just to get out here and not get to do the activity you've been breathlessly waiting to do since the last event?
Racer: Bob in Rainbows?
Org: Yup
Racer: $50?
Org: Yup
Racer: Thanks!

Usually it never gets that far and people are off like a shot as soon as you tell them "Bob in Rainbows" the first time. When people get to the track, after all of the preparation that goes into it, there're ready to throw fairly large amounts of money at a problem to get it to go away.

Get the right camera

[RightwingNutjob]

QR codes are the right idea. The real money you'll need to spend is on the camera and near-realtime PC to process it.

I've had good luck using GigEVision under Linux. There's a bunch of vendors out there that have Linux drivers for their GigEVision cameras and the specialized acquisition hardware is just an ethernet card. You probably want something that goes at least 30 fps sustained (probably about 1-3k for a camera, depending on resolution and bells and whistles). That's plenty enough to be able to interpolate vehicle trajectories between frames to get down to millimeter accuracy, assuming your optics package gives you the resolution.

Webcams are probably a no-go because you'll want higher resolution in order to be able to observe and recognize the codes over a wide finishline area, and USB 2.0 is limited in the amount of bandwidth you can get.

Just read the numbers

[oaksey]

I've heard about systems in cities that read number plates and time you between their different locations to see if you are speeding, I'm guessing a system like this could be used, just a matter of if it is cost effective or not.

Backup

[SEWilco]

The crucial data is the timing, while identification is a task. You must record the timing, but it is not crucial to perform the identification in real time, is it? You just need to be able to eventually produce the timed list. Record the timing and photo information in a way which lets you later review and compare both, so if you miss an identification it can be done later.

Yes, try to do the identification task immediately, but ensure that the system has the needed abilities to deal with problems. Rain, mud, or a bug on your lens could interfere with the intended operation.

Magnets? Maybe not

[SEWilco]

Identify unique shape, numbers, barcode, qr code or similar in the images, that have been attached using a magnet to the vehicle's door.

Not all vehicles are steel. Magnets might not hold your barcode on all vehicles.

Why not use RFID tags?

[blanchae]

Seems that RFID tags on the cars would solve that. No need to use facial recognition software - too complicated. In the railway industry they use barcodes on the side of railcars to keep track of them. That's another inexpensive idea. Just have the cars go single file through a laser barcode reader or through the local supermarket checkout...

Reread the summary

[thegarbz]

• Timer stops as it crosses finish line

What exactly is the problem here?

Was already mentioned in the summary question. Transponder location is the problem. You fall down on the detection of where the finish line is.

Eh. What?

[adolf]

Find me someone intimately familiar with an Android phone, or barcodes, or RFID, who can also grok basic SQL, and somone intimately familiar with the particular practical difficulties of SCCA timing, and I'll have your solution in-place, tested and working, before lunch.

This isn't rocket surgery.

(And if you give us until supper, it might even have a fancy web interface.)

Why reinvent the wheel?

[Killer99]

the timing and identification of race entrants or individuals is a very easy thing... this has been solved using RFID tag's to identify the entrants and the same timing devices to actually do the timing...

All of this is too complicated

[mswope]

How about a big QR code on each door and a camera hooked up to a laptop at the way-points?

Three suggestions based sorted by financial trade

[sulimma]

I can think of three options:
1) Expensive, but available immediately:
There is license plate reading software in use on highways in Europe. These turnpike systems use cameras to read the license plates and LIDAR 3D laser scanners to reliably measure the size of a truck. The lase information should provide very reliable timing data, but likely are an overkill.
As others suggested special markers on the cars could be easier to identify then license plates.

2) cheaper in development but higher material cost for each race
Put an android phone with GPS in each car and write a small app that tells the measurement system when they are approaching the goal line.

3) very low deployment cost but more development cost
Paint an reflective bar code on the side of the car. A fixed laser is pointing across the goal line. Connect the light detector picking up the reflection to a sound board. This will give you 25us accuracy on the timing and the pattern of the reflection will tell you which car it is. The system will even get you a very accurate speed measurement.

Options 1 and 2 only tell you the ordering of the cars. Detailed timing must be measured with another system. It might be sufficient to interpolate camera frame data.

Combining some techniques

[synoniem]

Based on a beam triggered start and finish you could use a still camera with a timestamp and a clock in sight. At the same time place a tag on all cars on the same height and distant from the front of the car. Combine a visual tag with a RFID tag in one and you have double signalling of both start and finish. Comparing those two can be done in milliseconds when connected to a laptop and only uses a networked connection between the two laptops.

Work together?

[ewanm89]

I would couple the beams with RFID tag (tag identifies the car, while the beams do all the timing). I would also suggest maybe getting together with another club and sharing the gear or a local university (with this one could probably get them to help make up a good system). As long as you choose separate race days. I'd also imagine quick setup and dismantle is needed?

I'll Try This

[Wingsy]

Get two line lasers. Modulate the beams at 20kHz for the start beam and 22kHz for the finish line beam. Direct the beams from overhead down to the start/finish lines. Design a timer/detector (I'll volunteer whenever I have time!) whose receptor is at least 1 inch in length and mount that to the top of each car. Each detector also has a small radio transmitter and a unique ID code.

When the car passes under the start beam the timer is started and is stopped when under the stop beam. At the stop beam the transmitter sends the ID and the E.T. (staggered so no 2 cars would omit at the same time).

Now, this isn't one of those races where the cars are covered in mud at the finish line, is it?

Re:I'll Try This

[Wingsy]

mmmmm.... "omit" = "transmit"

Barcodes on the car

[Paul Rutland]

Stick a different 2D barcode on each car, mount a camera in a location that can see the barcode at the finish line. When the car crosses the finish line, take a picture and search for the barcode.

Fill out the requirements!

[Nightwraith]

So many things missing from the OP's requirements like:

Must work in ALL weather conditions (fog, rain, snow, dust)
Must be accurate to 1 ms
Must identify which DRIVER is in the car as more than one person may be driving any given car, and drivers may have full face helmets
Must handle backward/spinning/sliding finishes
Must process in near realtime ( 20sec between finishes)
Must handle multiple cars on course at once (at least 3 running)
Must handle GoKarts and other strange pieces of machinery that may not have roof/hood/doors
Portable/Lightweight/Packable

What else is my caffeine starved brain missing?

Re:Eh. What?

[Nightwraith]

I'm your Huckleberry.

Cat got your tongue? Don't want to spill the beans?
Why not outline some basics of your design and we'll help identify where the weaknesses are. Cause there's a HUGE hole there right now...

Break up the problem

[Sez Zero]

I'm timed races with AMB systems and I own an AMB transponder for my race car, which are more expensive than the RC versions. The problem is front money. But my old region had dozens of transponders that they'd rent to participants for a nominal fee. I'm sure they made up the cost of a transponder from the rental monies.

Why not break the problem down into two parts?

First, use the existing photocell equipment for timing the vehicles start and end times. These are cheap and proven; I know a lot of autos clubs use or have previous used these. Second, use your web cams at the pre-start and cool down lane to grab a face to ensure that the start and stop times correspond to the same driver. Then the system can adjust for cars that DNF, and you could probably figure out the problem of someone walking through the lights in software.

Every auto-x I've been to has a starter. Just have that person ask "Ready? Ok, look here for your picture" and send them on the course. Remember that you'll also want to be able to identify the drivers AND the cars for cases where two drivers share a car (which is no uncommon in my area). Car is also important to make sure the specific driver is driving the right car for the class entered. Also add a camera to the cool-down lane and have a person there, or design the lane such that people will be looking at a certain spot, your camera.

Failing that, what about RFID tags? Swipe on course, swipe off. That could be cheated, so perhaps the webcam could be backup enforcement of the actual driver.

Re:Question asker is retarded

[Jumperalex]

Because you know nothing. Most systems are too expensive for grassroots racing, even your so called "cheap solutions".

Use E-Tag with existing Light beam system

[AussieJimbo]

Light beam gives accurate timing. E-Tag (as used in motorway tolling) identifies the car. http://en.wikipedia.org/wiki/E-TAG http://en.wikipedia.org/wiki/DSRC Software matches the potentially less precise E-Tag activation time to the accurate light beam detection and you have your car and time recorded.

There are special cameras for this

[Wyzard]

I don't know how timing is normally done for auto races, but I've been part of the staff at a few track & field events, such as the Nike Indoor Nationals, and seen how the timing is done there. There's a special camera that captures a single column of pixels, carefully aligned with the finish line, that records a rapid sequence of images whenever something changes in its field of view. The software assembles all these one-pixel-wide images into a single image whose horizontal axis is time rather than space. You can clearly see each runner, though arms and legs often look a little curved since they're moving as they pass through the plane of the finish line. In particular, the ID number tags worn by each runner are clearly visible.

Recognition isn't automatic, but it doesn't need to be. The operator just clicks on the front of each runner's shoulder (the part that "counts" for finishing the race) and reads the number from the runner's ID tag, and the time value associated with that column of pixels is recorded as that runner's finish time. So there's a human delay involved in matching the time measurements to the runners, but no human delay in the measurements themselves.

The company that did the timing at the races where I worked was CFPI Timing, and the tech page on their website has lots of details. Apparently the camera system I described is made by FinishLynx.

Multiple-Exposure

[jtara]

Several posts have objected to the frame rates of consumer video cameras as limiting resolution. However, this can be overcome.

For one, there are high-speed cameras with much higher frame rates. They are quite costly, though, and not necessary for this applicaiton.

I propose you use a multiple-exposure camera. Such things do exist in the digital world. Charge is allowed to accumulate for an extended period. You use a strobe to produce multiple images. You can use an infrared strobe to avoid disturbing participants.

In either case, much more light will be needed than with conventional video, because of the short exposure times. So, I don't know how practical this would be in terms of lighting.

I have experience with this technique in another sport, that involves hitting a small ball on a grass course... Said balls can travel at 100mph or higher, so we are in the range.

Re:Multiple-Exposure

[jtara]

Two companies that I think may make suitable cameras:

http://www.jai.com/EN/Pages/home.aspx
http://www.teledynedalsa.com/mv/products/cameras.aspx

I might as well add a plug for my favorite machine-vision camera dealer. Very helpful folk:

http://www.aegis-elec.com/

It's been a few years since I've been involved in this stuff, and I'm sure there is new technology. For one, similar cameras are now available with image intensifiers, which helps solve the illumination problem.

Easy - RFID

[Big Smirk]

Contestants (be it cars, people whatever) have an RFID tag (probably passive, 900Mhz RFID) in a name tag or other tag (tag on dash of car) that will give you decent interval timing.

For the finish line, or where timing is more critical, you can supplement with a camera (photo finish if you will).

900Mhz RFID is typically good for 15+ feet (depending on the size of the tag) and can be used reliably up to about 45 feet (big tag on big metal object - like a rail car). Tags can be very cheap - about 25 cents. To 'track humans' you need to keep the tags off the skin (skin detunes/absorbes RF energy) so you need a slightly thicker name tag (foam backed) for reliable reading at range.

Oh, and its already been done. I believe runners right now use a low frequency RFID tag tied to their shoe laces and they have to run over a mat. Low frequency RFID is based more on magnetic fields - thus short range only.

As for cheating, the top competitors in a marathon are watched pretty carfully and their are lots of witnesses. The people running it for themselves.... well who cares if they cheat. Sorta like using an aim-bot on single player mode.

ANPR

[badzilla]

http://www.automaticnumberplaterecognition.co.uk/

Divide and conquer

[Half-pint HAL]

You're on the right track here, but let's divide the task into subtasks.

We don't need to produce a fully automated solution at the first iteration, so we set up the webcams and the beam-gates with synchronised clocks. Post-race, the software is used by the marshalls to verify timing thus: it lines up a table of screen grabs, each row representing what it thinks is one car, the marshall clicks "OK" if they all match, or either clicks a button to identify a "drop out" (at which point the following photos are shuffled down to following rows) or an overtake (in which case the remainder of the row is switched with the corresponding images in the next row).

This solution is dead straightforward and lets you use the equipment and optimise webcam position for clear images, and gives you an immediate efficiency improvement, rather than moving straight to a completely new automated setup that will undoubtedly fail and probably be rejected by the competitors and organisers as being pointless.

When you find a suitable OCR or barcode solution, you will have the infrastructure in place to run it in parallel with the computer-aided-manual process, so you can iron out the difficulties without causing any serious disruption to the administration of the race.

HAL

Use a flash

[Inoen]

A couple of suggestions:

Get a digital camera, that can be triggered externally, with low (and known) latency.
Use a flash. It will 1) eliminate the need for shutter speed and 2) illuminate the scene so the camera can use a small aperture, and not need auto focus.
Use barcodes as identifying symbols - there is plenty of barcode scanning software. Turn it "sideways" if needed for further robustness against motion blur
Print the barcode on a reflective material. Then it could easily be the brightest spot in the photo - easy to identify.