If I drive from home to the University of Surrey and you want to know where I am at a given time on my journey then if you know my speed and what time I left home you should be able to calculate roughly where I have got to. (Bear in mind that the queue at the Costa coffee at Exeter Services can be desperately slow, so perhaps factor in a random variable for that). However, if you want to know where I am exactly at any given time, you will not be able to know how fast I am going at that point because in effect you have to stop time at the moment you want to know where I am, in order to accurately calculate my position. And similarly if you want to know how fast I am travelling (relative to the road, I believe) you will have to accept that my position at that time will remain approximate, since calculation of my speed requires that I am moving past any given point as you catch me on your speed camera.
If you want to subvert these complications of quantic information gathering, you could just call me on my mobile, and I can let you know both my position and speed at any time. Maybe understanding the subtleties of quantum theory is merely about being correctly selective about who, or what, you ask the questions of.
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