The point over which a level is centered is called a
a. station mark
b. transit
c. plumb line
d. point of reference

  D.  Point of reference

Explanation:

A point of reference used as a starting point for determining locations of objects at a construction site or in an area being surveyed will often be located on the above-ground portion of a station mark. The transit used for making the survey measurements will be leveled, and centered over the point of reference using a plumb line.

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answer: if though all maps are biased we study them to tell we have to go and use them to tell the direction we have to go but if you don't want to use a compass to find the way to go then the only option is to use the standard maps made by the european's  

explanation: