Reference:
http://wiki.openstreetmap.org/wiki/ Slippy_map_tilenames#Zoom_levels
Brief overview:
OSM tiles are 256x256 pixel PNG files.
Filename (URL) format is http://tile.openstreetmap.org/zoom/x/y.png
where
zoom=zoom-level-integer (from 0 to 19),
x=longitude-locator-integer (non-negative column number),
y=latitude-locator-integer (non-negative row number).
In the link above, see sample code to calculate x and y for a given zoom-level and a given latitude and longitude.
The following map of the Greek island
Naxos
(and the island of
Paros to the west) is done
with map tiles at OSM zoom level 12.
Approximate latitude,longitude of Naxos:
37.05 , 25.48 degrees
Each OSM tile is a 256x256 PNG file.
Each zoom-level-12 tile is one image of
2^12 x 2^12 = 4096 x 4096 = 16,777,216 images ~ 16 million images
which are used by OpenStreetMap to cover most of the Earth.
These zoom-level-12 tiles go from
x-numbers 2333 to 2342. (10 columns)
These zoom-level-12 tiles go from
y-numbers 1591 to 1597. (7 rows)
Total: 10 x 7 = 70 tiles
Image width: 10 x 256 = 2,560 pixels
Image height: 7 x 256 = 1,792 pixels
These tiles are fetched from the
OSM server when you (re)load this page.
So these tiles form an image using
the latest versions of the OSM tiles.
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Here is a link to the OSM (openstreetmap.org)
'slippy map'
for
Naxos (Wikipedia link) --- initially at zoom-level 10 and
centered at latitude and longitude 37.05 25.48,
near the center of the island.
Page created 2019 Feb 10.