http://gonintendo.com/?p=80601

EA boasts that Grand Slam Tennis will not require calibration between rounds, unlike Sega's Virtua Tennis 2009. Instead, calibration will be done on the fly without input from the player as the match loads. This comes Shortly after Sega brags that Virtua Tennis '09's implementation of Wii MotionPlus controls will not require buttons to be pressed during gameplay.

I'm guessing that EA's using gravity as a reference point to make sure the gyros stay on course during the match.

Will this influence anybody's decision on which tennis game they'll buy? Would you rather press buttons during the game, or in between points?

You can only use gravity to calibrate pitch and roll, but not yaw, ie not on the horizontal plane. They can use the IR pointing to correct the horizontal drift without the player pressing any button, but even this won't work if the player keeps the wiimote pointing offscreen for a long while.

What werekitten says is true.

For it to callibrate "on the fly" it woulneed you to point at the screen on occasion.... so it depends how fast it can callibrate and whether it can do it during fast motion.

If it can callibrate fast/in motion then I suppose it won't matter as the likely hood is you will point at the screen quite a bit in a Tennis game.

If not, then it really doesn't matter too much that you have to let it callirate at the start of a match as in Virtua Tennis, it's no more hassle than going through an extra menu screen.

Yes, I understand that gravity will only provide a reference point for two planes, but given that Virtua Tennis wants IR calibration for every point rather than every match, this suggests that EA has a clever trick for extending the period between calibrations. I would think that relying on sweeps past the sensor bar during gameplay is even less reliable than gravity. It's pure speculation on my part, but I think that regular sampling of the direction of gravity, in conjunction with sensor data on acceleration and orientation, might be used to pull it off.

I guess another possibility is that EA has simply designed their game not to require as much sensor precision as Virtua Tennis. It makes sense when you consider their reliance on buttons.

Its a war, always trying to outdo eachother. One will have a big flaw (not sure what it is yet) And I will get the other one.

It's not really a big deal, both games will be great and I could see both selling well too.

if i get either one, it'll be Virtua Tennis, in support of SEGA and all their awesomeness (barring any major flaws)

Shouldn't invisible calibration be the norm anyway?

Just because I'm curious, do we have any info on how much the M+ gyros drift?

There isn't much info on the IDG-600 gyroscope out there yet. The best I could find is this Ars Technica article:

http://arstechnica.com/gaming/news/2008/08/wii-motion-sensor.ars

"When you think of gyroscopes today, though, especially with regard to heading information, they're around $300,000 and are capable of accuracy of ten-thousandths of a degree per hour so that a 747 after an eleven hour flight can land where it's supposed to land," explained Virginia. "Game controllers, such as what Nintendo has selected, don't need that kind of accuracy. What they were looking for something in the area of one-tenth of a degree per second. [The IDG-600 gryo in the MotionPlus] measure up to 1500 degrees per second; it offers accuracy and full-range motion. We worked towards [a cost of] $1 per axis."

One-tenth of a degree per second would drift up to 6 degrees in a minute of play, or a full 90 degrees in 15 minutes. Invensense's PR guy seems to be talking about Nintendo's minimum spec with that sentence, though, so it may not describe the IDG-600's actual capabilities.