You can use any you like - it just means there may, or may not, be lots of zeros before, or after, a decimal point.
A sensible unit to use (to avoid lots of zeros and provide a reasonable degree of accuracy) would be millimetres (mm).
meters
It depends on the distance between the two points. If it is more than a kilometer apart then you would use kilometer. Unless you wanna do it with centimeter. It's just whatever is easier.
No, a foot is not a metric measurement. Metric measurements of length would include millimeter, centimeter, meter, and kilometer.
The distance between two towns can be measured in either imperial or metric units of length. Imperial unit would be miles, whilst the metric unit would be kilometres.
the measurer
Meters
distance
A global positioning system (GPS)
meters
I would assume that you would use cm or even mm if you wanted to be more accurate
A metric ruler.
Kilometers
kilometers
meters
Metres (in a built-up area), kilometres if across open spaces.
Miles is best.
A calculator would be between 100 and 150 millimetres.