Using zoom math 500 how to#
Now for an example of how to use the above data. Why this is level 24 was chosen I don't know however as someone else here worked out 0 gets you down to one 256 pixel tile for the earth.
Using zoom math 500 32 bit#
32 bit integers are also efficient to store and process. This is a logical choice as it yields global accuracy to about one centimeter which is plenty for aerial imagery. They then took that and divided it by a full 32 bit integer. (note in a previous post someone used a value of 40,075,160 I've seen this in Wikipedia a few places and it's incorrect. So back 15-20 year ago someone took WGS-84 as base data. What you need for these images to be used with any accuracy is to know the dimension of each pixel then scale the image according to whatever your overlaying it with. Scale ratios are relative to printed documents not computer screens. Well its not really a legitimate question to start with. Unit at Latitude = (Cosine of Latitude) X (Unit at Equator)
Zoom level 24 uses 2 to the 32 power (4,294,967,296) pixels at circumference.Įquatorial Circumference / 2 32 =. for zoom level N, the scale is one half of that of zoom level N-1.for zoom level 1, the scale is one half of that of zoom level 0.so the point is that the scale depends on your monitor's PPI and on the latitude (because of the Mercator projection).You cannot observe this in Google Maps since it automatically moves to the zoom level 1, but you can see it on OpenStreetMap's map (it uses the same tiling scheme).ģ60 degress on the Equator are equal to Earth's circumference, 40,075.16 km, which is 40075160 mĭivide 40075160 m with 0.065 m and you'll get 616313361, which is a scale of zoom level 0 on the Equator for a computer monitor with 100 DPI On zoom level 0, the whole 360 degrees of longitude are visible in a single tile.
That means 256 pixels are roughly 6.5 cm of length. Let's say your computer monitor has 100 pixels per inch (PPI). Google's web map tile has 256 pixels of width.To help you understand the maths (not a precise calculation, it's just for illustration):
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