I’m trying to move a shape along an equirectangular projection by converting the pixels into spherical coordinates, moving them, and then converting them back. Its been a while since I’ve done any kind of mathematics like this, so I’m sure I’m doing something wrong or using the wrong equations or something, I just don’t know what.

This is what I’m trying to achieve:

when the sphere in 3d space looks like:

here’s the code for moving the points:

def __move_point(point, width, height, dx, dy): # dx and dy are in degrees
    lat, long = __convert_to_lat_long(point[0], point[1], width, height)
    
    new_lat = lat + dy
    new_long = long - dx
    
    new_lat = np.clip(new_lat, -90, 90) # np is numpy
    if new_long < -180:
        new_long += 360
    elif new_long > 180:
        new_long -= 360
        
    return __convert_to_xy(new_lat, new_long, width, height)

def __convert_to_lat_long(x, y, width, height):
    latitude = (0.5 - (y / height)) * 180
    longitude = ((x / width) - 0.5) * 360
    return (latitude, longitude)

def __convert_to_xy(lat, long, width, height):
    x = (long / 360 + 0.5) * width
    y = (0.5 - lat / 180) * height
    return (int(x), int(y))

This however doesn’t cause any polar distortion, only translates the shape up/down. Before image:

and after I run the code:

There’s a lot of information on how to do this with Cartesian coordinates, but I’m not using Cartesian coordinates on purpose.