I made some graphs of the windgradient - that is how much the wind speed changes when going higher above the surface.
These are the standard wind gradients, meaning how they are if the weather is "normal", without wind shear or layer/temp. effects of any kind.
I've taken into account that the water surface gets more rough, when the wind picks up.
It is very evident, that a hand held anemometer can be very erroneous, because the wind speed changes so rapidly in "hand" height, especially in high winds.
And there is always some kind of shore effect, where the wind will be slowed down when reaching the shore (where you most likely are measuring).
If the anemometer is placed on a flagpole in 7-8 meters height, the readings will often be quite accurate, regardless of ground level errors.
The shore effect still exist - but is often very small in this height.
This is common knowledge to most of you, I know - but there are many who will find it useful.
Here is the graph, which is very interesting for ALL of us, I think:
If you want it in meter and m/s (European):
If you want it in feet and knots:
I've measured and checked these wind gradients on many weather stations and wind mill's here in Denmark, and it is often quite accurate - although there can be wind shear that makes it different - but not very often.