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83 lines
1.3 KiB
JavaScript
83 lines
1.3 KiB
JavaScript
/**
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* @module ol/proj/Units
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*/
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/**
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* Projection units: `'degrees'`, `'ft'`, `'m'`, `'pixels'`, `'tile-pixels'` or
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* `'us-ft'`.
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* @enum {string}
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*/
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const Units = {
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/**
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* Radians
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* @api
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*/
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RADIANS: 'radians',
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/**
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* Degrees
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* @api
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*/
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DEGREES: 'degrees',
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/**
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* Feet
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* @api
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*/
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FEET: 'ft',
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/**
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* Meters
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* @api
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*/
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METERS: 'm',
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/**
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* Pixels
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* @api
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*/
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PIXELS: 'pixels',
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/**
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* Tile Pixels
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* @api
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*/
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TILE_PIXELS: 'tile-pixels',
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/**
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* US Feet
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* @api
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*/
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USFEET: 'us-ft',
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};
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/**
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* See http://duff.ess.washington.edu/data/raster/drg/docs/geotiff.txt
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* @type {Object<number, Units>}
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*/
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const unitByCode = {
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'9001': Units.METERS,
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'9002': Units.FEET,
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'9003': Units.USFEET,
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'9101': Units.RADIANS,
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'9102': Units.DEGREES,
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};
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/**
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* @param {number} code Unit code.
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* @return {Units} Units.
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*/
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export function fromCode(code) {
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return unitByCode[code];
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}
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/**
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* Meters per unit lookup table.
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* @const
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* @type {Object<Units, number>}
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* @api
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*/
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export const METERS_PER_UNIT = {};
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// use the radius of the Normal sphere
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METERS_PER_UNIT[Units.RADIANS] = 6370997 / (2 * Math.PI);
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METERS_PER_UNIT[Units.DEGREES] = (2 * Math.PI * 6370997) / 360;
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METERS_PER_UNIT[Units.FEET] = 0.3048;
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METERS_PER_UNIT[Units.METERS] = 1;
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METERS_PER_UNIT[Units.USFEET] = 1200 / 3937;
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export default Units;
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