How to get bounds of a google static map?

Question

How to get bounds in degrees of google static map which has been returned, for example, for following request

http://maps.googleapis.com/maps/api/staticmap?c         


        

Answer 1

Thanks Marcelo for your answer. It has been quite helpful. In case anyone would be interested, here the Python version of the code (a rough translation of the PHP code, probably not as pythonic as it could be):

from __future__ import division
import math
MERCATOR_RANGE = 256

def  bound(value, opt_min, opt_max):
  if (opt_min != None): 
    value = max(value, opt_min)
  if (opt_max != None): 
    value = min(value, opt_max)
  return value


def  degreesToRadians(deg) :
  return deg * (math.pi / 180)


def  radiansToDegrees(rad) :
  return rad / (math.pi / 180)


class G_Point :
    def __init__(self,x=0, y=0):
        self.x = x
        self.y = y



class G_LatLng :
    def __init__(self,lt, ln):
        self.lat = lt
        self.lng = ln


class MercatorProjection :


    def __init__(self) :
      self.pixelOrigin_ =  G_Point( MERCATOR_RANGE / 2, MERCATOR_RANGE / 2)
      self.pixelsPerLonDegree_ = MERCATOR_RANGE / 360
      self.pixelsPerLonRadian_ = MERCATOR_RANGE / (2 * math.pi)


    def fromLatLngToPoint(self, latLng, opt_point=None) :
      point = opt_point if opt_point is not None else G_Point(0,0)
      origin = self.pixelOrigin_
      point.x = origin.x + latLng.lng * self.pixelsPerLonDegree_
      # NOTE(appleton): Truncating to 0.9999 effectively limits latitude to
      # 89.189.  This is about a third of a tile past the edge of the world tile.
      siny = bound(math.sin(degreesToRadians(latLng.lat)), -0.9999, 0.9999)
      point.y = origin.y + 0.5 * math.log((1 + siny) / (1 - siny)) * -     self.pixelsPerLonRadian_
      return point


def fromPointToLatLng(self,point) :
      origin = self.pixelOrigin_
      lng = (point.x - origin.x) / self.pixelsPerLonDegree_
      latRadians = (point.y - origin.y) / -self.pixelsPerLonRadian_
      lat = radiansToDegrees(2 * math.atan(math.exp(latRadians)) - math.pi / 2)
      return G_LatLng(lat, lng)

#pixelCoordinate = worldCoordinate * pow(2,zoomLevel)

def getCorners(center, zoom, mapWidth, mapHeight):
    scale = 2**zoom
    proj = MercatorProjection()
    centerPx = proj.fromLatLngToPoint(center)
    SWPoint = G_Point(centerPx.x-(mapWidth/2)/scale, centerPx.y+(mapHeight/2)/scale)
    SWLatLon = proj.fromPointToLatLng(SWPoint)
    NEPoint = G_Point(centerPx.x+(mapWidth/2)/scale, centerPx.y-(mapHeight/2)/scale)
    NELatLon = proj.fromPointToLatLng(NEPoint)
    return {
        'N' : NELatLon.lat,
        'E' : NELatLon.lng,
        'S' : SWLatLon.lat,
        'W' : SWLatLon.lng,
    }

Usage :

>>> import MercatorProjection
>>> centerLat = 49.141404
>>> centerLon = -121.960988
>>> zoom = 10
>>> mapWidth = 640
>>> mapHeight = 640
>>> centerPoint = MercatorProjection.G_LatLng(centerLat, centerLon)
>>> corners = MercatorProjection.getCorners(centerPoint, zoom, mapWidth, mapHeight)
>>> corners
{'E': -65.710988,
'N': 74.11120692972199,
'S': 0.333879313530149,
'W': -178.210988}
>>> mapURL = "http://maps.googleapis.com/maps/api/staticmap?center=%f,%f&zoom=%d&size=%dx%d&scale=2&maptype=roadmap&sensor=false"%(centerLat,centerLon,zoom,mapWidth,mapHeight)
>>> mapURL
http://maps.googleapis.com/maps/api/staticmap?center=49.141404,-121.960988&zoom=10&size=640x640&scale=2&maptype=roadmap&sensor=false'