61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
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#pragma once
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#include "Library.h"
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#include <cstdint>
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#include <optional>
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#include <span>
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#include <string>
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#include <vector>
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namespace CesiumGeospatial {
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class Cartographic;
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/**
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* @brief Loads and queries heights from an Earth Gravitational Model 1996
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* (EGM96) grid.
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*
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* EGM96 is a standard geopotential model of the earth's surface, which can be
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* used to obtain an approximation of the mean sea level (MSL) height at any
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* location on Earth.
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*/
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class CESIUMGEOSPATIAL_API EarthGravitationalModel1996Grid final {
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public:
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/**
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* @brief Attempts to create a {@link EarthGravitationalModel1996Grid} from the given buffer.
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*
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* This method expects the buffer to contain the contents of the WW15MGH.DAC
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* 15-arcminute grid. It must be at least 721 * 1440 * 2 = 2,076,480 bytes.
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* Any additional bytes at the end of the buffer are ignored.
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*
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* @returns The instance created from the buffer, or `std::nullopt` if the
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* buffer cannot be interpreted as an EGM96 grid.
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*/
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static std::optional<EarthGravitationalModel1996Grid>
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fromBuffer(const std::span<const std::byte>& buffer);
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/**
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* @brief Samples the height at the given position.
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*
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* @param position The position to sample. The `height` is ignored.
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* @returns The height (in meters) of the EGM96 surface above the WGS84
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* ellipsoid. A positive value indicates that EGM96 is above the ellipsoid's
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* surface, while a negative value indicates that EGM96 is below the
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* ellipsoid's surface.
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*/
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double sampleHeight(const Cartographic& position) const;
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private:
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EarthGravitationalModel1996Grid(std::vector<int16_t>&& gridValues);
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/**
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* Returns the height of the given grid value, in meters.
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*/
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double getHeightForIndices(size_t vertical, size_t horizontal) const;
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std::vector<int16_t> _gridValues;
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};
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} // namespace CesiumGeospatial
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