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 Darien CT area map is done
with map tiles at OSM zoom level 12.
The map includes Stamford, Greenwich, and Port Chester
to the west,
and Norwalk, Westport, Fairfield, and Bridgeport
to the east.
Approximate latitude,longitude of Darien city:
41.0511, -73.4791 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.
The zoom-level-12 tiles go from
x-numbers 1209 to 1215. (7 columns)
The zoom-level-12 tiles go from
y-numbers 1531 to 1537. (7 rows)
Total: 7 x 7 = 49 tiles
Image width: 7 x 256 = 1,792 pixels
Image height: 7 x 256 = 1,792 pixels
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Here is a link to the OSM (openstreetmap.org)
'slippy map'
for
Darien, CT --- initially at zoom-level 12 and
centered at latitude and longitude 41.0511 -73.4791.
Page was created 2016 Oct 30.
Page was changed 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.)