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34 lines
1.3 KiB
JavaScript
34 lines
1.3 KiB
JavaScript
/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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import roundDecimal from './roundDecimal';
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export const EARTH_CIRCUMFERENCE_KM = 40075.16;
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export const MILES_PER_KM = 1.60934;
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export function kmToPixels(kilometers, latitude, zoomLevel) {
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// Algorithm from: http://wiki.openstreetmap.org/wiki/Zoom_levels
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const latitudeRad = latitude * (Math.PI / 180);
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// Seems like the zoomLevel is off by one
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const kmPerPixel =
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(EARTH_CIRCUMFERENCE_KM * Math.cos(latitudeRad)) / 2 ** (zoomLevel + 9);
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return roundDecimal(kilometers / kmPerPixel, 2);
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}
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