geodesk::Mercator Class Reference

Methods for working with Mercator-projected coordinates. More...

#include <Mercator.h>

Static Public Member Functions
static int32_t	xFromLon (double lon) noexcept
	Converts longitude (in WGS-84 degrees) to a Mercator X-coordinate.
static int32_t	xFromLon100nd (int lon) noexcept
	Converts WGS-84 longitude (in 100-nanodegree increments) to a Mercator X-coordinate.
static int32_t	yFromLat (double lat) noexcept
	Converts latitude (in WGS-84 degrees) to a Mercator Y-coordinate.
static int32_t	yFromLat100nd (int lat) noexcept
	Converts WGS-84 latitude (in 100-nanodegree increments) to a Mercator Y-coordinate.
static double	roundTo100nd (double deg) noexcept
static double	lonFromX (double x) noexcept
	Converts a Mercator X-coordinate to longitude (in WGS-84 degrees).
static double	roundedLonFromX (double x) noexcept
	Converts a Mercator X-coordinate to longitude (in WGS-84 degrees, rounded to 7 digits of precision).
static double	latFromY (double y) noexcept
	Converts a Mercator Y-coordinate to latitude (in WGS-84 degrees).
static double	roundedLatFromY (double y) noexcept
	Converts a Mercator Y-coordinate to latitude (in WGS-84 degrees, rounded to 7 digits of precision).
static double	scale (double y) noexcept
	Calculates the scaling factor for the given Y-coordinate.
static double	metersPerUnitAtY (double y) noexcept
	Calculates the number of meters each Mercator unit represents at the given Y-coordinate.
static double	unitsFromMeters (double meters, double atY) noexcept
	Calculates the number of Mercator units represented by the given distance (in meters), at the given Y-coordinate.

Static Public Attributes
static constexpr double	MAP_WIDTH = 4'294'967'294.9999
static constexpr double	EARTH_CIRCUMFERENCE = 40'075'016.68558
static constexpr double	MIN_LAT = -85.0511288
static constexpr double	MAX_LAT = 85.0511287
static constexpr int32_t	MIN_LAT_100ND = -850511288
static constexpr int32_t	MAX_LAT_100ND = 850511287
static constexpr int32_t	MIN_Y = INT_MIN
static constexpr int32_t	MAX_Y = INT_MAX - 1

Detailed Description

Methods for working with Mercator-projected coordinates.

GeoDesk uses a Pseudo-Mercator projection that projects coordinates onto a square Cartesian plane 2^32 units wide/tall (in essence, the value range fully uses a 32-bit signed int). This projection is compatible with Web Mercator EPSG:3857, except that instead of meters at the Equator, it uses a made-up unit called "imp" ("integer, Mercator-projected").

Member Function Documentation

latFromY()

static double geodesk::Mercator::latFromY ( double y )

inlinestaticnoexcept

Converts a Mercator Y-coordinate to latitude (in WGS-84 degrees).

lonFromX()

static double geodesk::Mercator::lonFromX ( double x )

inlinestaticnoexcept

Converts a Mercator X-coordinate to longitude (in WGS-84 degrees).

metersPerUnitAtY()

static double geodesk::Mercator::metersPerUnitAtY ( double y )

inlinestaticnoexcept

Calculates the number of meters each Mercator unit represents at the given Y-coordinate.

The Y-coordinate must be between INT_MIN and INT_MAX (inclusive), or the result will be undefined.

Parameters

y	valid Y-coordinate

roundedLatFromY()

static double geodesk::Mercator::roundedLatFromY ( double y )

inlinestaticnoexcept

Converts a Mercator Y-coordinate to latitude (in WGS-84 degrees, rounded to 7 digits of precision).

roundedLonFromX()

static double geodesk::Mercator::roundedLonFromX ( double x )

inlinestaticnoexcept

Converts a Mercator X-coordinate to longitude (in WGS-84 degrees, rounded to 7 digits of precision).

roundTo100nd()

static double geodesk::Mercator::roundTo100nd ( double deg )

inlinestaticnoexcept

scale()

static double geodesk::Mercator::scale ( double y )

inlinestaticnoexcept

Calculates the scaling factor for the given Y-coordinate.

This factor is 1 at the equator and progressively increases towards the polar regions, and is used to compensate for the distortion introduced by the Mercator projection.

unitsFromMeters()

static double geodesk::Mercator::unitsFromMeters ( double meters, double atY )

inlinestaticnoexcept

Calculates the number of Mercator units represented by the given distance (in meters), at the given Y-coordinate.

The Y-coordinate must be between INT_MIN and INT_MAX (inclusive), or the result will be undefined.

Parameters

meters	distance in meters
atY	valid Y-coordinate

xFromLon()

static int32_t geodesk::Mercator::xFromLon ( double lon )

inlinestaticnoexcept

Converts longitude (in WGS-84 degrees) to a Mercator X-coordinate.

xFromLon100nd()

static int32_t geodesk::Mercator::xFromLon100nd ( int lon )

inlinestaticnoexcept

Converts WGS-84 longitude (in 100-nanodegree increments) to a Mercator X-coordinate.

yFromLat()

static int32_t geodesk::Mercator::yFromLat ( double lat )

inlinestaticnoexcept

Converts latitude (in WGS-84 degrees) to a Mercator Y-coordinate.

yFromLat100nd()

static int32_t geodesk::Mercator::yFromLat100nd ( int lat )

inlinestaticnoexcept

Converts WGS-84 latitude (in 100-nanodegree increments) to a Mercator Y-coordinate.

Member Data Documentation

EARTH_CIRCUMFERENCE

double geodesk::Mercator::EARTH_CIRCUMFERENCE = 40'075'016.68558

staticconstexpr

MAP_WIDTH

double geodesk::Mercator::MAP_WIDTH = 4'294'967'294.9999

staticconstexpr

MAX_LAT

double geodesk::Mercator::MAX_LAT = 85.0511287

staticconstexpr

MAX_LAT_100ND

int32_t geodesk::Mercator::MAX_LAT_100ND = 850511287

staticconstexpr

MAX_Y

int32_t geodesk::Mercator::MAX_Y = INT_MAX - 1

staticconstexpr

MIN_LAT

double geodesk::Mercator::MIN_LAT = -85.0511288

staticconstexpr

MIN_LAT_100ND

int32_t geodesk::Mercator::MIN_LAT_100ND = -850511288

staticconstexpr

MIN_Y

int32_t geodesk::Mercator::MIN_Y = INT_MIN

staticconstexpr

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The documentation for this class was generated from the following file:

• C:/dev/libgeodesk/include/geodesk/geom/Mercator.h