![]() ![]() A Guinness commercial in which the transition from cosmic back to everyday scale is achieved by a galaxy turning into a swirl of froth on a glass of Guinness.Fuji TV's sign-off sequence used in the early 1970s features a zoom out from a replica of the Fuji TV building note the original one in Kawada to the surface of the moon in a recreation of the famous "Earthrise" photo taken from Apollo 8. One created for CBLT (a CBC affiliate) in Toronto in the 1980s features a zoom-in from space on the city of Toronto as the streets of the downtown area dissolve into a shot of the city skyline, particularly the CN Tower. While not technically "ads," some TV stations have used variations of this as station identifications.The second half was a zoom back in, to the call's recipient in central Manhattan. The first half of a 1980s British Telecom commercial was a zoom out, from a man telephoning from an office in central London to the entire western hemisphere.Mapbox GL–based libraries uses 512×512-pixel tiles by default, so Mapbox GL zoom levels are one fewer than the zoom levels described above that are used by other tools. The error also does not take into account additional differences caused by variation of the altitude on ground, or by the irregular variations of the geographic polar axis, and other errors caused by celestial tidal effects and climatic effects on the average sea level, or by continent drifts, major earthquakes, and magmatic flows below the crust). But this error is very slight: it is null on the reference Equator, then grows to an absolute maximum of 0.3% at median latitudes, then shrinks back to zero at high latitudes towards poles. This formula assumes that the Earth is perfectly spheric, but since the Earth is actually ellipsoidal there will be a slight error in this calculation, which does not take into account the flattening (with a slight reduction of radius for the best-fitting sphere passing at geographic poles at average sea level). C should be expressed in whatever scale unit you're interested in (miles, meters, feet, smoots, whatever). Make sure your calculator is in degrees mode, unless you want to express latitude in radians for some reason. S pixel = S tile / 256 = C ∙ cos( latitude) / 2 ( zoomlevel + 8) For example on the equator and at zoom level 0, we get 40 075 016.686 / 256 ≈ 156 543.03 (in meters per pixel). Where C means the equatorial circumference of the Earth ( 40 075 016.686 m ≈ 2π ∙ 6 378 137.000 m for the reference geoid used by OpenStreetMap).Īs tiles are 256-pixels wide, the horizontal distance represented by one pixel is: S tile = C ∙ cos( latitude) / 2 zoomlevel The horizontal distance represented by each square tile, measured along the parallel at a given latitude, is given by: Such scale is typically used for the kind of area to represent on a single tile (Note that when rendering on the web, the standard CSS pixel size is defined at 96 PPI, browsers will rescale the images when needed but only by integer factors on PNG images to avoid making the rendered text or icons too fuzzy if the screen has a lower resolution, the rendered images may be larger and it's possible for a renderer to create image with other resolutions than 256 pixels at 96 PPI to better fit the expected sizes, and for a web interface to automatically select other available resolutions for Hi-DPI screens, but this requires more storage and computing resources on the server as well the zoom level in the formulas above do not necessarily need to be integers, and this may be used to get intermediate scales with tiles having more pixels). In addition, the given scales assume that 256-pixel wide tiles are rendered and will be dependent on the resolution of the viewing monitor: these values are for a monitor with a 0.3 mm / pixel (85.2 pixels per inch or PPI). "~ Scale" is only an approximate size comparison and refers to distances on the Equator.These values for "m / pixel" are calculated with an Earth radius of 6372.7982 km and hold at the Equator for other latitudes the values must be multiplied by the cosine (approximately assuming a perfect spheric shape of the geoid) of the latitude. Values listed in the column "m / pixels" gives the number of meters per pixel at that zoom level for 256-pixel wide tiles.The "° Tile width" column gives the map width in degrees of longitude, for a square tile drawn at that zoom level.This is useful when calculating storage requirements for pre-generated tiles. The "# Tiles" column indicates the number of tiles needed to show the entire world at the given zoom level. ![]() Variation with latitude of represented distances (in degrees or pixels) on the Mercator projection per actual distances (in meters) on Earth surface. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |