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 Gran Canaria:
27.97 , -15.60 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 1867 to 1873. (7 columns)
These zoom-level-12 tiles go from
y-numbers 1713 to 1719. (7 rows)
Total: 7 x 7 = 49 tiles
Image width: 7 x 256 = 1,792 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
Gran Canaria --- initially at zoom-level 10 and
centered at latitude and longitude 27.97 -15.60,
near the center of the island.
Page created 2016 Oct 30.
Page was chnaged 2018 Jul 08.
(Added 'slippy map' link.)
Page was changed 2019 Jan 11.
(Added css and javascript to try to handle text-size
for smartphones, esp. in portrait orientation.)
Page was changed 2019 Feb 10.
(HTML changes due to reorg of OSMmaps.)