Accuracy - How close a measurement is to the "True" measurement.

Precision - How repeatable a measurement is. 

Proper use of the proper tools will get accurate work, some of the time.
It is the installation of proper methods with these tools that produces
Precision. 

For instance, if a person drives to Colorado and marks the distance their odometer
tracks in mileage.  Then they turn around and drive the same path home they will
get the same mileage.  However, if their tires are not the exact same size the cars
computer has stored in its memory, they may have several miles variation from the
true distance. 
These same calculations are performed by our car to determine speed.  Ever wander
why you were pulled over and the Officer tells you that you were going faster than
your speedometer was indicating?
This can all be adjusted on the fly by simply marking your distances on your odometer
to the mile markers along the road. 
A fun test, if you have a long drive and want to occupy some of your minds time,
is to check your mileage over 10 miles to see if there is any discrepency. 
If the mile markers are 10, and the odomerter reads 9.6 miles.  You have
a 4% error.  You have gone 0.4 miles farther than your odometer told you.
At 70 miles per hour, that means you are actually going 2.8 miles and hour
faster than your speedometer says.  Your true speed is 72.8 miles per hour. 

These same theories apply to Surveyors. We should know our instruments are not perfect. 
With the proper methods and care, we can adjust for these "systematic" errors.