The technology driving telecasts just might surprise you.Fans of the sport say to truly appreciate NASCAR racing, you have to attend an event in person to see the cars whizzing by, hear and feel dozens of vehicles revving to over 9,000 rpm as they throttle up to the green flag at the start of the race, and smell the burnt rubber from a spinout or a tire-smoking victory celebration. The 91,000-plus fans sitting in the stands at last month's Nextel Cup race at New Hampshire International Speedway attest to the sensory experience of big-time auto racing. More technology from the NASCAR circuitBut the on-site crowd probably didn't know that on lap 21 Kasey Kahne got his red No. 9 car up to 157 mph on the front stretch before slowing down to a more leisurely 96 mph to take the curve. Or that Ricky Rudd's 21 car was traveling at precisely 67 mph when it hit the wall rear-end first on lap 211. Viewers at home had all this information and more courtesy of the on-screen graphics that were part of the TNT live coverage of the Siemens 300 race.Calculating and displaying real-time information such as speed takes more than a well-aimed radar gun and some quick hands on a keyboard. "It's the most complicated graphic to produce in television," says Bob Hess, track engineer for Sportvision, the Chicago technology company NASCAR contracts with to produce the real-time data and associated graphics for the television broadcasts.In the TV compound that sat just outside the grandstand behind Turn 3 at the New Hampshire course, Hess and his team of a half-dozen engineers sat in one of the 13 TV trucks on site to produce the race. Sportvision's truck is dedicated to receiving, compiling and distributing telemetry and position data from each car in the race and pushing it out to regular TV, pay-per-view, the Web and Nextel cellular phones.Each car is equipped with a GPS receiver embedded in the roof and a Data Acquisition and Positioning System (DAPS) black box mounted near the rear window that collects braking, throttle position and rpm information. Using a 900-MHz transmitter, the DAPS and GPS information is radioed to one of the three or four base stations positioned around the track. Multiple base stations are used for redundancy purposes, as objects in and around the track could block the signal. The telemetry data and GPS data is collected five times per second. To get from the base station to the truck, Sportvision taps into fiber cable connecting the camera positions around the track or a DSL modem connected to Category 3 cabling.Cat 3? "It's cheaper [than Cat 5] and it works," says Ken Milnes, senior vice president of engineering at Sportvision.Inside the truck, the communications controller (known as CC) aggregates all the data, including the official timing information from NASCAR, which is provided via an RS-232 serial interface. "CC organizes the data in a way that's useful for the other applications we run," Milnes says, adding that a proprietary format is used to store the data.A Cisco Catalyst switch connects Windows XP and Linux machines used to produce graphics. Coaxial cable feeds the graphics data to the other production trucks for the TV broadcast. A machine called T-Sync helps synchronize the time codes from the video feed with the GPS time data.Another challenge is to match the data with the car on screen as it traverses the 1.058-mile oval in roughly 30 seconds and is viewed from myriad camera positions. "As the camera is panning, tilting and zooming, we need to know what the camera is representing and where the car would be in the picture," Milnes says.Sportvision also creates the K-Zone for ESPN baseball coverage and the yellow first-down line used in football broadcasts. Those are a bit easier, given a baseball diamond and football field are relatively uniform in dimension from park to park. For racing, where all the tracks are different, three-dimensional topographical maps of all 23 tracks in the NASCAR Nextel Cup Series have been created from aerial surveys of the properties, and each camera has a GPS unit that tells the truck exactly where it's located. This lets Sportvision's computers know where the car is within 10 centimeters. It also lets TV viewers see cartoon-like thought bubbles follow cars around the track that show real-time speed and the "dot racing" graphic that shows how far a car is behind the leader on a graphical representation of the track.Sportvision also pushes the data out in a compact data format over a T-1 (with a back-up dial-up connection) to Turner Sports in New York, producers of the nascar.com site. Subscribers to the TrackPass service get a Java applet that shows the same data real-time telemetry information via the Internet. Pit Command, a graphical representation of the track and car positions, also is available on Nextel phones.Ironically, all but the official timing and GPS information is available during an event to the race teams, as NASCAR prohibits them from using real-time telemetry data, all in the name of parity and competition.Of course, the setup happens for 36 races almost every weekend over the course of the 10-month NASCAR season. Each track presents its own set of challenges for the crew. Although Williams Communications provides T-1 connectivity to the truck at each track using the same IP address (no need to reconfigure the on-board router), sometimes the local telco provider puts the physical line in the wrong place, which happened at the New Hampshire International Speedway this last time around. At Talledega Superspeedway in Alabama, one of the setup crew got lost for 2 hours in the sewer system while trying to run a cable under the track to the infield.With the data Sportvision provides, racing fans watching on TV or the Internet get a feel for how close these guys are when hurling around the track. On lap 49, there was a 3.26-second difference between the first-and fifth-place cars, and there were three cars between them. So much for the 2-second rule you learned in drivers ed.