diff options
Diffstat (limited to 'include/mbgl/util/projection.hpp')
| -rw-r--r-- | include/mbgl/util/projection.hpp | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/include/mbgl/util/projection.hpp b/include/mbgl/util/projection.hpp index eb45088580..0b6e9f6bf1 100644 --- a/include/mbgl/util/projection.hpp +++ b/include/mbgl/util/projection.hpp @@ -8,14 +8,20 @@ namespace mbgl { +// Spherical Mercator projection +// http://docs.openlayers.org/library/spherical_mercator.html class Projection { - public: + // Map pixel width at given scale. + static double worldSize(double scale) { + return scale * util::tileSize; + } + static double getMetersPerPixelAtLatitude(double lat, double zoom) { const double constrainedZoom = util::clamp(zoom, util::MIN_ZOOM, util::MAX_ZOOM); - const double mapPixelWidthAtZoom = std::pow(2.0, constrainedZoom) * util::tileSize; + const double constrainedScale = std::pow(2.0, constrainedZoom); const double constrainedLatitude = util::clamp(lat, -util::LATITUDE_MAX, util::LATITUDE_MAX); - return std::cos(constrainedLatitude * util::DEG2RAD) * util::M2PI * util::EARTH_RADIUS_M / mapPixelWidthAtZoom; + return std::cos(constrainedLatitude * util::DEG2RAD) * util::M2PI * util::EARTH_RADIUS_M / worldSize(constrainedScale); } static ProjectedMeters projectedMetersForLatLng(const LatLng& latLng) { @@ -32,7 +38,7 @@ public: } static LatLng latLngForProjectedMeters(const ProjectedMeters& projectedMeters) { - double latitude = (2 * std::atan(std::exp(projectedMeters.northing / util::EARTH_RADIUS_M)) - (M_PI / 2)) * util::RAD2DEG; + double latitude = (2 * std::atan(std::exp(projectedMeters.northing / util::EARTH_RADIUS_M)) - (M_PI / 2.0)) * util::RAD2DEG; double longitude = projectedMeters.easting * util::RAD2DEG / util::EARTH_RADIUS_M; latitude = util::clamp(latitude, -util::LATITUDE_MAX, util::LATITUDE_MAX); |