Map-Tile Tools in Python

tiletools.py

'''
A collection of Tile tools in python. 

Author: Daniel Ellis 2022
Contact: daniel.ellis.research (a-t) gmail (dot) com

Article: https://medium.com/p/e54de570d0bd

'''
import mpmath as mp



def get_tile(lat_deg,lon_deg,zoom):
    ''' 
    Get the corresponding tile to a given longitude and latitude
    '''
    lat_rad = mp.radians(lat_deg) #lat_deg * mp.pi / 180
    n = 2 ** zoom
    xtile = n * ((lon_deg + 180) / 360)
    ytile = n * (1 - (mp.log(mp.tan(lat_rad) + mp.sec(lat_rad)) / mp.pi)) / 2

    return 'tile: %d/%d/%d '%(zoom,xtile,ytile)


def tile_translator(z,x,y,newzoom):
   '''Find the linking (left top) most tile from another zoom level'''

   n = 2 ** z
   x /= n
   y /= n

   n2 = 2 ** newzoom
   x *= n2
   y *= n2
   return '%d/%d/%d'%(newzoom,x,y)


def get_children(z,x,y):
    ''' Return the children of a tile '''
    tile = list(map(int,(tile_translator(z,x,y,z+1).split('/'))))
    return [[tile[0],tile[1]+i,tile[2]+j] for i in [0,1] for j in [0,1]]


def tile2lon(z,x,y) :
    return x / 2**z * 360 - 180;


def tile2lat(z,x,y) :
    n = mp.pi - 2 * mp.pi * y / 2**z;
    return float((180 / mp.pi) * (mp.atan(0.5 * (mp.exp(n) - mp.exp(-n)))))


def tile_bbox(z,x,y):
    '''
    Return the bounding box of a tile
    '''
    w = tile2lon(z,x,y)
    s = tile2lat(z,x,y)
    e = tile2lon(z,x+1,y)
    n = tile2lat(z,x,y+1)

    return [w,s,e,n]