The largest city in each 10x10 degree latitude/longitude box

Re:The largest city in each 10x10 degree latitude/longitude box by roelschroeven on Thursday June 25, 2020 @05:28PM (#23645936)

I'm not 100% sure about that. Are angles between circles on a sphere defined by the angles between their tangent lines? If it were true, you could for each point/meridian combination construct an infinite amount of different circles that would all meet at right angles with that meridian (just vary the circle's radius). That doesn't feel quite right.

According to Wikipedia [1], "in spherical geometry, angles are defined between great circles". Meridians are great circles, but parallels are not. Possibly the angle is simply not defined for circles that are not great circles?

[1] https://en.wikipedia.org/wiki/Spherical_geometry

[ Parent | on HN ]

Re:The largest city in each 10x10 degree latitude/longitude box by tantalor on Thursday June 25, 2020 @06:20PM (#23646429)

It only matters what is the angle between the lines tangent to the curves at the point of intersection.

Here's an example: https://www.desmos.com/calculator/is7mush1ma

The red and blue circles are both perpendicular to the green circle at the origin.

[ Parent | on HN ]

Re:The largest city in each 10x10 degree latitude/longitude box by roelschroeven on Friday June 26, 2020 @05:23AM (#23650166)

OK, thanks, today I learned something new.

[ Parent | on HN ]