CODEWITHSUNDEEP
google-mapsmercator
Ufuk Ugur
Ufuk Ugur

Reputation: 346

calculate google maps tile boundary coordinates

I've made a lot of searches and found some useful resources but still having problems about calculation.

I want to calculate NE and SW coordinates for a specific tile.

This is my way :

Zoom = 11
x = 1188 
y = 767

number of tile = 2 ^ 11 (equals 2048)
angle1 = 360 / 2048
longitude = (1188 * angle1) - 180

it works correct.

But latitude part is not :

angle2 = 170.1022575596 / (2048/2)
latitude = ((2048 / 2) - 767) * angle2

thanks in advance

Upvotes: 3

Views: 1580

Answers (2)

Hong Cheng
Hong Cheng

Reputation: 370

Here I want to share a python version answer.

PS: [the last answer includes matlab and java implementations]

from math import atan, exp
z = 18.
x = 223576.
y = 101583.
pi = 3.1415926

alon1 = (x /pow(2.,z))*360.0 - 180.0
alon2 = ((x+1) /pow(2.,z))*360.0 - 180.0

an   = pi-2.*pi*y/pow(2.,z)
alat1 = 180.0/pi*atan(0.5*(exp(an)-exp(-an)))
an   = pi-2.*pi*(y+1)/pow(2.,z)
alat2 = 180.0/pi*atan(0.5*(exp(an)-exp(-an)))
print(alon1,alat1,alon2,alat2)

Upvotes: 0

karougeo
karougeo

Reputation: 21

The solution you are looking for is this:

z = 11
x = 1188 
y = 767

pi = 3.14159

alon1 = (x /2^z)*360.0 - 180.0
alon2 = ((x+1) /2^z)*360.0 - 180.0

an   = pi-2*pi*y/2^z
alat1 = 180.0/pi*atan(0.5*(exp(an)-exp(-an)))
an   = pi-2*pi*(y+1)/2^z
alat2 = 180.0/pi*atan(0.5*(exp(an)-exp(-an)))

And you get the NW (alon1,alat1) & SE (alon2,alat2) coordinates for this specific tile.

Upvotes: 2

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