How this iphone application works?

I am just looking iphone apps at apple store, and i have found this app g8, http://www.dynolicious.com/, but can you give some ideas or logic that how this app works, i mean how it is possible to measure car performance without using or communicating with any external hardware ...??? By using just hardware built into iphone, ie. a开发者_开发问答ccelerometer.

It works as follows. The data provided as results are actually estimates, not absolutely correct values measured attaching external hardware to the car. The estimates come from the GPS unit and the accelerometer embedded within the iPhone. Using the GPS you can estimate from the positions detected in different temporal instants the distance travelled and therefore the velocity. Then you can also estimate the acceleration using the accelerometer.

This is just a guess, but I would expect that you tell it your car make and model which will give the manufacturer's performance and fuel consumption figures. Then using the accelerometer and positional information in the phone you can calculate the speed of the car. A relatively simple equation can then be used to calculate the expected performance.

I would guess it uses the GPS to measure the 0-60 acceleration (start a stopwatch and stop when GPS says you're moving at 60 mph) and the built-in accelerometer to detect G-force. The horsepower estimate is just that - an estimate. They may have a performance table of various known cars and their 0-60 performance and horsepower. Based on that, they can give an estimate for yours.