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 Canary Islands map is done
with map tiles at OSM zoom level 12.
Approximate latitude,longitude of Tenerife:
28.26 , -16.60 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 1855 to 1864. (10 columns)
These zoom-level-12 tiles go from
y-numbers 1708 to 1715. (8 rows)
Total: 10 x 8 = 80 tiles
Image width: 10 x 256 = 2,560 pixels
Image height: 8 x 256 = 2,048 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
Tenerife (Wikipedia link) --- initially at zoom-level 10 and
centered at latitude and longitude 28.2686 -16.6055,
near the center of the island.
Page created 2019 Feb 10.