Accuracy of Google Map measuring tool

And other tools.

[fischermx]

Hi,

I want to measure a park, where I use to jog in the mornings.
I'm using Google Earth with the measure tool and it is 817 mts.

There's also another nice services called map24.com, which uses an applet on the browser and also has a measure tool. With that tool, the park is 842 mts.

Which do you think is more accurate?

I once measured with the car and it was 805mts, but I did not have the wheels on the size recommended by the manufactured, so I suppose it is invalid.

[radix]

Nike+, i. e. Nike + iPod?

[appi2]

Measure your own drive,garden,garage,house etc then compare that with the map maybe.