tile_math.cpp¶

file src/app/map/tile_math.cpp · Applications

Web Mercator (EPSG:3857) projection formulas behind the slippy-map tile arithmetic.

Source src/app/map/tile_math.cpp

Implements the spherical forward and inverse projection of the OpenStreetMap slippy map scheme and the ground resolution per pixel.

See also

Namespaces¶

Namespace	Description
`nmeasim::app::map`	The slippy-map view of the desktop application, part of `nmeasim::app`.

Declared or defined in this file and documented on the page of their namespace.

Member	Description
`nmeasim::app::map::tiles_at`	Returns the number of tiles along one axis at a zoom level, 2^`zoom`.
`nmeasim::app::map::tile_coordinates`	Returns the fractional tile coordinates of a position at a zoom level.
`nmeasim::app::map::pixel_coordinates`	Returns the pixel coordinates of a position at a zoom level.
`nmeasim::app::map::position_of_tile`	Returns the position at fractional tile coordinates at a zoom level, the inverse of `tile_coordinates`.
`nmeasim::app::map::position_of_pixel`	Returns the position at pixel coordinates at a zoom level, the inverse of `pixel_coordinates`.
`nmeasim::app::map::tile_at`	Returns the tile containing fractional tile coordinates, with x wrapped around the antimeridian.
`nmeasim::app::map::parent_of`	Returns the tile one zoom level up (one level less detailed) that contains a tile.
`nmeasim::app::map::wrap_longitude`	Wraps a longitude into [-180, 180), as the world repeats east and west.
`nmeasim::app::map::metres_per_pixel`	Returns the ground distance one pixel covers at a latitude and zoom level.

File-local functions

Name	Description
`to_radians()`	Converts an angle from degrees to radians.
`to_degrees()`	Converts an angle from radians to degrees.

File-local variables

Name	Description
`kEarthCircumferenceM`	Equatorial circumference of the Earth in metres: 2 pi times the WGS 84 semi-major axis of 6378137 m, the sphere Web Mercator projects from.

double to_radians(double degrees) noexcept

Converts an angle from degrees to radians.

Parameters

Name	Type	Description
`degrees`	`double`	Angle in degrees, any value.

Returns double: The angle in radians.

double to_degrees(double radians) noexcept

Converts an angle from radians to degrees.

Parameters

Name	Type	Description
`radians`	`double`	Angle in radians, any value.

Returns double: The angle in degrees.

double kEarthCircumferenceM{40075016.686}

Equatorial circumference of the Earth in metres: 2 pi times the WGS 84 semi-major axis of 6378137 m, the sphere Web Mercator projects from.