Classes
struct	TileKey

Functions
QDebug	operator<< (QDebug debug, const TileKey &key)
	Streams as slippy "zoom/x/y" notation for logging.

double	worldSize ()
	Full mercator world extent (2piR) in world meters.

QPointF	geoToWorld (const QGeoCoordinate &coord)
	Geo -> world meters. Latitude is clamped to +/-kMaxLatitude.

QGeoCoordinate	worldToGeo (const QPointF &world)
	World meters -> geo (altitude 0)

double	mercatorScale (double latitude)

bool	isValidKey (const TileKey &key)
	True if zoom is within [kMinZoom, kMaxZoom] and x/y address a tile at that zoom.

double	tileSpanAtZoom (int zoom)
	Edge length of one tile at zoom, in world meters.

QPointF	tileMinCorner (const TileKey &key)
	South-west (minimum x/y) corner of a tile in world meters.

TileKey	tileForWorld (const QPointF &world, int zoom)
	Tile containing a world point. World coordinates are clamped to the world extent.

double	metersPerPixelAtZoom (int zoom)
	World meters spanned by one pixel of a kTilePixels tile at zoom (equator)

int	zoomForMetersPerPixel (double metersPerPixel)
	Smallest zoom whose resolution is at least as fine as metersPerPixel (clamped to valid range)

size_t	qHash (const TileKey &key, size_t seed=0)

Variables
constexpr double	kEarthRadius = 6378137.0
	WGS84 equatorial radius (m)

constexpr double	kMaxLatitude = 85.05112878
	Mercator latitude clamp (deg)

constexpr int	kMinZoom = 0

constexpr int	kMaxZoom = 23

constexpr int	kTilePixels = 256
	Nominal tile edge used for meters-per-pixel.

Detailed Description

Web Mercator (EPSG:3857) projection and slippy-tile math for the GeoMap engine.

World space: mercator meters, origin at (lon 0, equator), x east, y north, z up. Note mercator meters are true meters only at the equator (scale grows with 1/cos(lat)); the rendered scene is self-consistent but distances are not geodesic.

Tile addressing: standard slippy scheme — tile (0,0) is the north-west corner, x grows east, y grows south.

Function Documentation

◆ geoToWorld()

QPointF TileMath::geoToWorld ( const QGeoCoordinate & coord )

Geo -> world meters. Latitude is clamped to +/-kMaxLatitude.

Definition at line 23 of file TileMath.cc.

References kEarthRadius, and kMaxLatitude.

Referenced by GeoMapCamera::centerForCoordinateAtScreenPoint(), GeoScene::scenePositionFor(), GeoScene::screenPositionFor(), GeoMapCamera::setCenter(), and SurfacePatchModel::terrainHeightAt().

◆ isValidKey()

bool TileMath::isValidKey ( const TileKey & key )

True if zoom is within [kMinZoom, kMaxZoom] and x/y address a tile at that zoom.

Definition at line 44 of file TileMath.cc.

References kMaxZoom, kMinZoom, TileMath::TileKey::x, TileMath::TileKey::y, and TileMath::TileKey::zoom.

Referenced by ElevationTilePyramid::bestTileFor(), HeightField::insertTile(), ElevationTilePyramid::insertTile(), TerrariumTileFetcher::requestPatchHeights(), ProceduralHeightSource::requestTile(), TerrariumTileFetcher::requestTile(), and HeightField::samplePatch().

◆ mercatorScale()

double TileMath::mercatorScale ( double latitude )

Mercator scale factor 1/cos(lat): how many mercator meters one true ground meter spans at the given latitude (clamped to +/-kMaxLatitude). Used to convert true-meter heights/altitudes into mercator scene units so vertical and horizontal geometry stay consistent away from the equator.

Definition at line 38 of file TileMath.cc.

References kMaxLatitude.

Referenced by GeoScene::verticalScale().