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Fix obfuscatedCoordinatesImpl helper (it returned values outside of offset radius)

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This commit is contained in:
Vesa Luusua 2018-09-14 14:38:06 +03:00
parent 8107016533
commit fcbffabbe5
1 changed files with 45 additions and 19 deletions
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64
src/util/maps.js
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@ -5,24 +5,41 @@ import config from '../config';
const { LatLng } = sdkTypes;
const EARTH_RADIUS = 6371000; /* meters */
const DEG_TO_RAD = Math.PI / 180.0;
const THREE_PI = Math.PI * 3;
const TWO_PI = Math.PI * 2;
const degToRadians = latlng => {
const { lat, lng } = latlng;
const latR = lat * DEG_TO_RAD;
const lngR = lng * DEG_TO_RAD;
return { lat: latR, lng: lngR };
};
const radToDegrees = latlngInRadians => {
const { lat: latR, lng: lngR } = latlngInRadians;
const lat = latR / DEG_TO_RAD;
const lng = lngR / DEG_TO_RAD;
return { lat, lng };
};
/**
* This obfuscatedCoordinatesImpl function is a temporary solution for the coordinate obfuscation.
* In the future, improved version needs to have protectedData working and
* available in accepted transaction.
*
* Based on:
* https://gis.stackexchange.com/questions/25877/generating-random-locations-nearby#answer-213898
*/
const obfuscatedCoordinatesImpl = (latlng, cacheKey) => {
const { lat, lng } = latlng;
const { lat, lng } = degToRadians(latlng);
const sinLat = Math.sin(lat);
const cosLat = Math.cos(lat);
// https://gis.stackexchange.com/questions/25877/generating-random-locations-nearby
const r = config.maps.fuzzy.offset / 111300;
const y0 = lat;
const x0 = lng;
// Two seeded random numbers to be used to calculate new location
// We need seeded so that the static map URL doesn't change between requests
// (i.e. URL is cacheable)
const u = cacheKey ? seedrandom(cacheKey)() : Math.random();
const v = cacheKey
const randomizeBearing = cacheKey ? seedrandom(cacheKey)() : Math.random();
const randomizeDistance = cacheKey
? seedrandom(
cacheKey
.split('')
@ -30,16 +47,25 @@ const obfuscatedCoordinatesImpl = (latlng, cacheKey) => {
.join('')
)()
: Math.random();
const w = r * Math.sqrt(u);
const t = 2 * Math.PI * v;
const x = w * Math.cos(t);
const y1 = w * Math.sin(t);
const x1 = x / Math.cos(y0);
const newLat = y0 + y1;
const newLng = x0 + x1;
// Randomize distance and bearing
const distance = randomizeDistance * config.maps.fuzzy.offset;
const bearing = randomizeBearing * TWO_PI;
const theta = distance / EARTH_RADIUS;
const sinBearing = Math.sin(bearing);
const cosBearing = Math.cos(bearing);
const sinTheta = Math.sin(theta);
const cosTheta = Math.cos(theta);
return new LatLng(newLat, newLng);
const newLat = Math.asin(sinLat * cosTheta + cosLat * sinTheta * cosBearing);
const newLng =
lng + Math.atan2(sinBearing * sinTheta * cosLat, cosTheta - sinLat * Math.sin(newLat));
// Normalize -PI -> +PI radians
const newLngNormalized = (newLng + THREE_PI) % TWO_PI - Math.PI;
const result = radToDegrees({ lat: newLat, lng: newLngNormalized });
return new LatLng(result.lat, result.lng);
};
const obfuscationKeyGetter = (latlng, cacheKey) => cacheKey;