Tile Specifications¶

Hierarchies/Levels¶

Tiles are split up into three levels or hierarchies. Hierarchy 0 contains edges pertaining to roads that are considered highway (motorway, trunk, and primary) roads and are stored in 4 degree tiles. Hierarchy 1 contains roads that are at a arterial level (secondary and tertiary) and are saved in 1 degree tiles. Finally, Hierarchy 2 contains roads that are considered at a local level (unclassified, residential, and service or other). These tiles are saved in .25 degree tiles.

So in python, the levels are defined as:
valhalla_tiles = [{'level': 2, 'size': 0.25}, {'level': 1, 'size': 1.0}, {'level': 0, 'size': 4.0}]

The World at Level 0¶

The following image shows the world at level 0. Using a world bounding box (-180, -90, 180, 90) the world is split up into 4 degree tiles. The rows and columns start from the bottom left and increase to the top right. Tiles are row ordered increasing from west to east.

Level 0 Image generated using http://geojson.io

Using a bounding box for Germany, Pennsylvania, and NYC we can show how the regions would be split up into the 3 levels. Level 0 is colored in light blue. Level 1 is light green and level 2 is light red.

Germany¶

Germany Image generated using http://geojson.io

Pennsylvania¶

Pennsylvania Image generated using http://geojson.io

NYC¶

NYC Image generated using http://geojson.io

Sample Tile Code¶

Below are some sample functions to help you obtain latitude and longitude coordinates, levels, tile ids, and list of tiles that intersect a bounding box.

#!/usr/bin/env python

valhalla_tiles = [{'level': 2, 'size': 0.25}, {'level': 1, 'size': 1.0}, {'level': 0, 'size': 4.0}]
LEVEL_BITS = 3
TILE_INDEX_BITS = 22
ID_INDEX_BITS = 21
LEVEL_MASK = (2**LEVEL_BITS) - 1
TILE_INDEX_MASK = (2**TILE_INDEX_BITS) - 1
ID_INDEX_MASK = (2**ID_INDEX_BITS) - 1
INVALID_ID = (ID_INDEX_MASK << (TILE_INDEX_BITS + LEVEL_BITS)) | (TILE_INDEX_MASK << LEVEL_BITS) | LEVEL_MASK

def get_tile_level(id):
  return id & LEVEL_MASK

def get_tile_index(id):
  return (id >> LEVEL_BITS) & TILE_INDEX_MASK

def get_index(id):
  return (id >> (LEVEL_BITS + TILE_INDEX_BITS)) & ID_INDEX_MASK

def tiles_for_bounding_box(left, bottom, right, top):
  #if this is crossing the anti meridian split it up and combine
  if left > right:
    east = tiles_for_bounding_box(left, bottom, 180.0, top)
    west = tiles_for_bounding_box(-180.0, bottom, right, top)
    return east + west
  #move these so we can compute percentages
  left += 180
  right += 180
  bottom += 90
  top += 90
  tiles = []
  #for each size of tile
  for tile_set in valhalla_tiles:
    #for each column
    for x in range(int(left/tile_set['size']), int(right/tile_set['size']) + 1):
      #for each row
      for y in range(int(bottom/tile_set['size']), int(top/tile_set['size']) + 1):
        #give back the level and the tile index
        tiles.append((tile_set['level'], int(y * (360.0/tile_set['size']) + x)))
  return tiles

def get_tile_id(tile_level, lat, lon):
  level = list(filter(lambda x: x['level'] == tile_level, valhalla_tiles))[0]
  width = int(360 / level['size'])
  return int((lat + 90) / level['size']) * width + int((lon + 180 ) / level['size'])

def get_ll(id):
  tile_level = get_tile_level(id)
  tile_index = get_tile_index(id)
  level = list(filter(lambda x: x['level'] == tile_level, valhalla_tiles))[0]
  width = int(360 / level['size'])
  height = int(180 / level['size'])
  return int(tile_index / width) * level['size'] - 90, (tile_index % width) * level['size'] - 180

Get the Level or Hierarchy¶

get_tile_level(73160266) returns a level of 2. 73160266 is a Valhalla Graphid.
get_tile_level(142438865769) returns a level of 1. 142438865769 is an Open Traffic Segment id.

Get the Latitude and Longitude from an ID¶

get_ll(73160266) returns the bottom left corner of the level 2 tile. (41.25, -73.75)
get_ll(142438865769) returns the bottom left corner of the level 1 tile. (14.0, 121.0)

Get the Tile ID from a Latitude, Longitude, and Level¶

get_tile_id(0, 14.601879, 120.972545) 2415 Tile would be on disk with the directory structure of /0/002/415.gph
get_tile_id(1, 14.601879, 120.972545) 37740 Tile would be on disk with the directory structure of /1/037/740.gph
get_tile_id(2, 41.413203, -73.623787) 756425 Tile would be on disk with the directory structure of /2/000/756/425.gph

Get Tile ID from an ID¶

get_tile_index(73160266) Returns the tile id 756425.
get_tile_index(142438865769) Returns the tile id 37741.

Get Tiles That Intersect a Bounding Box¶

tiles_for_bounding_box(-74.251961,40.512764,-73.755405,40.903125) Returns a list of tiles for the NYC bounding box at each level.
[(2, 752102), (2, 753542), (2, 752103), (2, 753543), (2, 752104), (2, 753544), (1, 46905), (1, 46906), (0, 2906)]