coordinates.h

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/* Copyright 2018-2019 TomTom N.V., 2014 Gareth Cross

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. */

#pragma once

#include <cmath>
#include <stdexcept>
#include <string>
#include <tuple>

#include "mercator.h"

struct WGSCoordinate
{
  double lat, lon;
};

template <typename NumericType = int>
struct TileCoordinateGeneric
{
  NumericType x, y;
};

template <typename NumericType = int>
TileCoordinateGeneric<NumericType> fromWGSCoordinate(WGSCoordinate coord, int zoom)
{
  if (zoom > MAX_ZOOM)
  {
    throw std::invalid_argument("Zoom level " + std::to_string(zoom) + " too high");
  }
  else if (coord.lat < -85.0511 || coord.lat > 85.0511)
  {
    throw std::invalid_argument("Latitude " + std::to_string(coord.lat) + " invalid");
  }
  else if (coord.lon < -180 || coord.lon > 180)
  {
    throw std::invalid_argument("Longitude " + std::to_string(coord.lon) + " invalid");
  }

  double constexpr rho = M_PI / 180;
  double const lat_rad = coord.lat * rho;

  TileCoordinateGeneric<NumericType> ret;
  int const n = 1 << zoom;
  ret.x = n * ((coord.lon + 180) / 360.0);
  ret.y = n * (1 - (std::log(std::tan(lat_rad) + 1 / std::cos(lat_rad)) / M_PI)) / 2;
  return ret;
}

template <typename NumericType = int>
WGSCoordinate toWGSCoordinate(TileCoordinateGeneric<NumericType> coord, int zoom)
{
  WGSCoordinate ret{ 0, 0 };
  ret.lon = coord.x / std::pow(2.0, zoom) * 360.0 - 180;
  double n = M_PI - 2.0 * M_PI * (1 + coord.y) / std::pow(2.0, zoom);
  ret.lat = 180.0 / M_PI * std::atan(0.5 * (std::exp(n) - std::exp(-n)));
  return ret;
}

template <typename NumericType>
bool operator==(TileCoordinateGeneric<NumericType> self, TileCoordinateGeneric<NumericType> other)
{
  return std::tie(self.x, self.y) == std::tie(other.x, other.y);
}
template <typename NumericType>
bool operator>=(TileCoordinateGeneric<NumericType> self, TileCoordinateGeneric<NumericType> other)
{
  return std::tie(self.x, self.y) >= std::tie(other.x, other.y);
}
template <typename NumericType>
bool operator<=(TileCoordinateGeneric<NumericType> self, TileCoordinateGeneric<NumericType> other)
{
  return std::tie(self.x, self.y) <= std::tie(other.x, other.y);
}

using TileCoordinate = TileCoordinateGeneric<int>;