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Xiaobian to share with you what are the slice formats in GIS development, I believe most people still do not know how, so share this article for everyone's reference, I hope you have a lot of harvest after reading this article, let's go to understand it together!

Two common slice formats: 1. Based on Mercator coordinate system (Web Mercator EPSG:3857) Map manufacturers: Google Maps, Bing Maps, Gaode, Baidu, Arcgis Online, etc. 2. Based on WGS84 coordinate system (WGS1984 EPSG:4326) Map manufacturers: Google Earth, etc.

Open source map frameworks such as Openlayers, Cesium, maptalks, Lealet, etc. support service loading in both tile formats.

Detailed map slice service description URL:

http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification

http://wiki.osgeo.org/wiki/WMS_Tiling_Client_Recommendation

http://msdn.microsoft.com/en-us/library/bb259689.aspx

http://code.google.com/apis/maps/documentation/overlays.html#Google_Maps_Coordinates

Web Mercator EPSG:3857 Slice Generation Algorithm Description:

Extent of web mercator coordinate system:

[-20037508.342789244, -20037508.342789244, 20037508.342789244, 20037508.342789244], in meters;

20037508.342789244 From the circumference of the earth wgs84 coordinate system range:

[-180 90, 180, 90] in degrees.

latitude and longitude coordinates web mercator metric unit pixel slice

LatLon Meters Pixels Tile

First of all, the latitude and longitude should be converted into metric units of web mercator. The image to be cut is a picture with large pixels, and there is a coordinate range of latitude and longitude. In this way, the pixel and metric coordinate range should be converted. Finally, the corresponding slice should be generated. When converting web mercator coordinates to latitude and longitude, the maximum latitude coordinate is 85.05112878, and the range greater than this coordinate or less than this negative coordinate is clipped. The corresponding web mercator conversion range to latitude and longitude is: [-180, -85.05112878, 180, 85.05112878], so, load the web mercator slice onto the sphere, and there will be two unsealed holes in the north and south poles.

。

The first level zoom=0 of the web mercator slice, some also start from zoom=1, the size of the slice is set to 256*256, corresponding to the above mentioned web mercator coordinate range, and the resolution of the first level is:

initialResolution=20037508.342789244*2/ 256 = 156543.03392804062

After each magnification level, the corresponding first resolution/2 is used. These resolution levels are schemes that can be used to make slice software, such as Arcgis Server, Geoserver, etc.

TMS defines the slice starting from the bottom left corner of the map, i.e. the origin is at the bottom left corner; Google Maps defines the slice center at the top left corner; QuadTree is a slice naming format used by Bing Maps; TMS and Google Maps store and read maps in the form of x\y\z; QuadTree converts x\y into binary form for storage and reading; the principle is the same, but the naming rules are different. The above is all the content of this article "What are the slice formats in GIS development?" Thank you for reading! I believe that everyone has a certain understanding, hope to share the content to help everyone, if you still want to learn more knowledge, welcome to pay attention to the industry information channel!

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