3 ms·
Interesting historical exploration! The medieval debate on whether North, East or South should be at the top of the map could be linked to the disagreement on t
by georgecmu 13y ago
Interesting historical exploration! The medieval debate on whether North, East or South should be at the top of the map could be linked to the disagreement on the East/North coordinate system convention of the modern day: ENU vs NED.
Generally, land vehicles use the ENU (East-North-Up) convention, with East corresponding to the X axis and Z axis point up (against the gravity vector), while sea and aircraft use the NED (North-East-Down) convention, with X axis pointing North, and Z axis pointing down, aligned with the gravity vector.
- einhverfr 13y agoInterestingly they didn't get to a real explanation. It ended with the idea that for reasons lost to history, Ptolomy appears perhaps to have originated the practice. The thing is, I don't think that is lost to history. Ptolomy was amazingly meticulous and while he didn't spell out why, he was very clear about enough details I think this could be pieced together further.
- couchand 13y agoRegardless of the east vs. north distinction, I find it very unnatural to have an increasing vertical coordinate correspond to a movement towards the earth, if for no other reason that calling sea level zero and using mainly positive numbers above seems very convenient (for any vehicle except submarines).
- 7952 13y agoIf you are measuring sea depth it doesn't make sense to have a minus sign when most of your values will be negative. Also, it is important to remember that sea level is an entirely arbitrary concept that depends on your frame of reference. On nautical charts elevations are usually measured against the lowest tide level which will be different to the datum on GPS (for example).