Measuring a quantity using two measuring devices

I would like to ask how I can reduce uncertainty by designing an experiment.

I need to measure a quantity( say speed, in m/s). I have to calibrate the device and then move the device to measure this.

I would like to reduce the uncertainty by using two devices to measure the same quantity.

If I calibrate the devices together, I will be able to find how correlated they are to each other.

I then can move both devices to measure the same point - how do I combine the uncertainties of these devices?

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spiff.rit.edu/classes/phys273/uncert/uncert.html may be useful towards the end (the example about repeating a banana cream pie). Do you know the uncertainty of one device? Are you expecting the same value for the both devices? If I'm not mistaken you're looking to essentially get multiple measurements for a value without repeating the whole experiment to improve the accuracy of your measurement? – Folau Aug 6 '13 at 10:29
I am looking into getting multiple measurements of a value without repeating the whole experiment to improve the accuracy of the measurement. I know the uncertainty of the devices, so the idea is to 1) Calibrate the devices together to find how correlated they are to each other 2) place both devices so that they point(laser) to the same point that will measure the same m/s ---- will this be the best setup to reduce the uncertainty when compared to using only one measurement device? – user2165209 Aug 6 '13 at 10:48