I installed jSpeed and speedo and both of them are showing a speed from 1 to 7 km/h while I stay still . I rebooted the phone and it doesn't solve anything . Is this a bug ? It could be fixed ?

Which speeds do you get if you are moving? Preferably in a vehicle with known speed.

Depending on how the software calculates the speed and how it handles different satellite visibility, there might be several reasons for the results you're getting.

Well , while being in a car it shows correctly because I watched the speedometer of car and the jSpeed and they shows same speed , but while standing still it shows unstable speeds from 1 to 7 km/h , and few times 0 .

Its the rotation of the earth/satellites I would think. At the equator the earth moves at about 25 km/h

I also think it's related to the accuracy of the gps measurement (thus also to the amount of satellites you've locked on to). I'm guessing it could be somehow tinkered to look nicer on the speedometer software but probably at the expense of accuracy of the reading in really slow speeds.

The earth's circumference is, roughly, 40000 km at the equator.

It makes a full turn in, roughly, 24 hours.

So, the earth moves at, roughly, 1700km/h at the equator.

The moving while stationary thing has been a problem for as long as GPS has existed. The math is complicated just as much as the reasons are for the problem - there are a long list of factors that are difficult to eliminate, so every measurement will have error.

Some units will go in to averaging mode when they think you are stationary - convolving all the points in to an ellipse of error with you in the middle more or less at zero kph, others just give it to you raw. If you track this slow movement you'll see the points all roughly surround where you actually are.

It's not a bug, it can't be fixed, it's just a result of some amazing human ingenuity, the accuracy of it is astounding. Though I do understand when you feel it isn't :-)

I meant to write per min wrote per hour in stead. So its 28 km/m and change at the equator. Times that number by the cosine of latitude and that is the speed where you are.