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96 lines
2.9 KiB
Python
96 lines
2.9 KiB
Python
"""
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Geo projection.
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"""
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from typing import Optional
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import numpy as np
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from map_machine.geometry.boundary_box import BoundaryBox
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__author__ = "Sergey Vartanov"
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__email__ = "me@enzet.ru"
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def pseudo_mercator(coordinates: np.ndarray) -> np.ndarray:
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"""
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Use spherical pseudo-Mercator projection to convert geo coordinates into
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plane.
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:param coordinates: geo positional in the form of (latitude, longitude)
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:return: position on the plane in the form of (x, y)
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"""
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y: float = (
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180 / np.pi * np.log(np.tan(np.pi / 4 + coordinates[0] * np.pi / 360))
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)
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return np.array((coordinates[1], y))
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def osm_zoom_level_to_pixels_per_meter(
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zoom_level: float, equator_length: float
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) -> float:
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"""
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Convert OSM zoom level to pixels per meter on Equator. See
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https://wiki.openstreetmap.org/wiki/Zoom_levels
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:param zoom_level: integer number usually not bigger than 20, but this
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function allows any non-negative float value
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:param equator_length: celestial body equator length in meters
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"""
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return 2 ** zoom_level / equator_length * 256
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class Flinger:
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"""
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Convert geo coordinates into SVG position points.
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"""
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def __init__(
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self,
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geo_boundaries: BoundaryBox,
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zoom_level: float,
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equator_length: float,
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) -> None:
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"""
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:param geo_boundaries: minimum and maximum latitude and longitude
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:param zoom_level: zoom level in OpenStreetMap terminology
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:param equator_length: celestial body equator length in meters
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"""
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self.geo_boundaries: BoundaryBox = geo_boundaries
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self.ratio: float = 2 ** zoom_level * 256 / 360
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self.size: np.ndarray = self.ratio * (
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pseudo_mercator(self.geo_boundaries.max_())
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- pseudo_mercator(self.geo_boundaries.min_())
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)
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self.pixels_per_meter: float = osm_zoom_level_to_pixels_per_meter(
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zoom_level, equator_length
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)
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self.size: np.ndarray = self.size.astype(int).astype(float)
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def fling(self, coordinates: np.ndarray) -> np.ndarray:
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"""
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Convert geo coordinates into SVG position points.
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:param coordinates: vector to fling
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"""
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result: np.ndarray = self.ratio * (
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pseudo_mercator(coordinates)
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- pseudo_mercator(self.geo_boundaries.min_())
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)
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# Invert y axis on coordinate plane.
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result[1] = self.size[1] - result[1]
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return result
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def get_scale(self, coordinates: Optional[np.ndarray] = None) -> float:
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"""
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Return pixels per meter ratio for the given geo coordinates.
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:param coordinates: geo coordinates
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"""
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if coordinates is None:
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# Get pixels per meter ratio for the center of the boundary box.
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coordinates = self.geo_boundaries.center()
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scale_factor: float = abs(1 / np.cos(coordinates[0] / 180 * np.pi))
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return self.pixels_per_meter * scale_factor
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