Today, longitudes on earth are counted east or west of Greenwich, Great Britain.
This prime meridian results from two facts: that Britannia ruled the waves, and that its kings owned land and buildings in Greenwich. The choice is as logical as was choosing the arm of some king as unit length for the realm. The latter was repaired after the French revolution, when the metre was defined as the ten millionth part of the distance from the North pole to the equator. So instead of the King (whose physical measurements, in the French case, were also dramatically altered by the revolution), it was mother Earth who defined the unit length, in a logical way. I propose to do the same for the prime meridian, having it pass through the highest point on the equator. The logic is easy to understand: the equator has a physical meaning for any celestial body, and the highest point on it is the best observable. (Also the longest observable should the planet be drowned.) For planet earth, this point, 4.690 metres above sea level, is situated on the southern slopes of the Cayambe volcano in Ecuador. To make things easy for space travelers or clumsy surveyors: Cayambe is the only spot on the Equator with snow cover.
Greenwich is 77°59′31″ east of the newly proposed prime meridian. To translate the King's longitude to the Earth's, add or subtract this number. The arithmetic would be simpler, if at the same time we abandoned the Babylonian subdivision of degrees in minutes and seconds, and simply wrote 77.9919°. I hesitate to recommend the revolutionary subdivision of the circle in 400 centesimal degrees (or gons) instead of 360 Babylonian degrees. It's revolutionary all right (along with months of 30 days each, and days of 10 hours each) but mathematics, unlike Revolutionary Man, has no particular inclination towards counting in tens. An equilateral triangle has angles of 60 Babylonian degrees, which translates into 66.6666 gons; halving it gives rise to a triangle with angles of 30, 60 and 90 Babylonian degrees, which is 33.333, 66.666 and 100 gons, respectively. On the other hand, there is Nature's strong hint: at last, both the right angle and the boiling temperature of water would be 100 degrees!