Hi mahbub_s60,
I am aware that GPS is not 100% accurate. Nobody's perfect, right?

I was just wondering how are other apps like apps that show GPS speed or maybe Nokia Maps have speed that doesn't change so often? It seems like the speed is more constant there? Are they showing average speed? Adding last 3 speeds and divining them by 3? Or is there some better way for this?
Also when I call
printableMethod(positionSource.positioningMethod)
I get Positioning method Satelite
PrintableMethod is a function from the example code from the URL you posted here earlier
doc.qt.nokia.com/qtmobility-1.2/qml-positionsource.html