ellipsoid.hpp

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/*
 * Copyright (c) 2023, NVIDIA CORPORATION.
 *
 * 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
 *
 * https://apache.ac.cn/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 <cassert>
#include <cmath>
 
namespace cuproj {


template <typename T>
struct ellipsoid {
 ellipsoid() = default;

 constexpr ellipsoid(T a, T inverse_flattening) : a(a)
  {
 assert(inverse_flattening != 0.0);
 b = a * (1. - 1. / inverse_flattening);
 f = 1.0 / inverse_flattening;
 es = 2 * f - f * f;
 e = sqrt(es);
 alpha = asin(e);
 n = pow(tan(alpha / 2), 2);
  }
 
 T a{}; // 半长轴
 T b{}; // 半短轴
 T e{}; // 第一偏心率
 T es{}; // 第一偏心率平方
 T alpha{}; // 角偏心率
 T f{}; // 扁率
 T n{}; // 第三扁率
};

template <typename T>
constexpr ellipsoid<T> make_ellipsoid_wgs84()
{
 return ellipsoid<T>{T{6378137.0}, T{298.257223563}};
}

 
} // 命名空间 cuproj