• cheeseburger@lemmy.ca
      link
      fedilink
      English
      arrow-up
      2
      ·
      6 months ago

      10,152 Km between Atlanta and Tbilisi, and ChatGPT gave the pseudocode below as an explanation, which I didn’t double check before making this comment!

      
      # Coordinates for Atlanta, Georgia, USA
      atlanta_coords = (33.7490, -84.3880)
      
      # Coordinates for Tbilisi, Georgia (country)
      tbilisi_coords = (41.7151, 44.8271)
      
      # Calculate the straight line distance through the Earth
      geopy.distance.great_circle(atlanta_coords, tbilisi_coords).km```
      • Gobbel2000@programming.dev
        link
        fedilink
        English
        arrow-up
        4
        ·
        6 months ago

        That’s wrong, it calculates the surface distance not the distance through the earth, while claiming otherwise. From the geopy.distance.great_circle documentation:

        Use spherical geometry to calculate the surface distance between points.

        This would be a correct calculation, using the formula for the chord length from here:

        from math import *
        
        # Coordinates for Atlanta, West Georgia
        atlanta_coords = (33.7490, -84.3880)
        # Coordinates for Tbilisi, Georgia
        tbilisi_coords = (41.7151, 44.8271)
        
        # Convert from degrees to radians
        phi = (radians(atlanta_coords[0]), radians(tbilisi_coords[0]))
        lambd = (radians(atlanta_coords[1]), radians(tbilisi_coords[1]))
        
        # Spherical law of cosines
        central_angle = acos(sin(phi[0]) * sin(phi[1]) + cos(phi[0]) * cos(phi[1]) * cos(lambd[1] - lambd[0]))
        chord_length = 2 * sin(central_angle/2)
        
        earth_radius = 6335.439 #km
        print(f"Tunnel length: {chord_length * earth_radius:.3f}km")
        

        A straight tunnel from Atlanta to Tbilisi would be 9060.898km long.

      • gmtom@lemmy.world
        link
        fedilink
        English
        arrow-up
        3
        ·
        edit-2
        6 months ago

        Depends what the great circle function does. But chances are it gives you the arc length between the two points, which would give you the shortest distsnce between them on the surface of the earth.

        If you wanted the distance through the earth you would need to work put the central angle of that arc, then use that to work out the remaining edge of the triangle formed between the two cities and the centre of the earth.