Which of the following have led to the advancement of mapmaking techniques?

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Which of the following have led to the advancement of mapmaking techniques?
a.compass, astrobale camera satellite and computer
b. Vand de graf generator and tesla coil
c.Plow and cotton gin
d. Weathervane and barometer 

Compasses were used as early as 1040 by the Song Dynasty as a way of navigating and mapping the vast oceans in their sea adventures. Astrolabes were used find the exact location of ships by referring to the celestial bodies. Camera satellites and computers are used nowadays to create very accurate maps that people can readily access and update.  

2pi more meters because you find the circumference which is 6pi and 4pi and subtract it and you get 2pi

The answer is gross domestic product. hope this