rough location filter with same minimum/maximum lattitude/longitude range

geoFilterDiscretteCache.js

"use strict";

const EARTH_RADIUS = 6371;

function degToRad(deg) {
  return deg * Math.PI / 180;
}
/**
 * @param {Number} distance km
 * @returns {Number}
 */
function approximateLatitude(distance) {
  return 180 * distance / EARTH_RADIUS / Math.PI;
}

/**
 * Return min/max lat/lon for approximately search by coordinates
 *
 * @param {Number} distance MUST be fixed for caching, km
 * @param {Number} latitude search point center
 * @param {Number} longitude search point center
 * @returns {{latMin: number, latMax: number, lonMin: number, lonMax: number, latIgnore: boolean, lonIgnore: boolean}}
 */
function approximateDistance(distance, latitude, longitude) {
  const lat = parseFloat(latitude);
  const lon = parseFloat(longitude);

  const deltaLat = approximateLatitude(distance);//сдвиг по широте
  let tmpLon = Math.abs(lat) + deltaLat;
  const resMinLat = Math.floor((lat - deltaLat) / deltaLat) * deltaLat;
  const resMaxLat = Math.ceil((lat + deltaLat) / deltaLat) * deltaLat;

  tmpLon = Math.ceil(tmpLon / deltaLat) * deltaLat;//ближе к экватору
  if (tmpLon > 90) {
    tmpLon = 90;
  }
  const r = EARTH_RADIUS * Math.cos(degToRad(tmpLon));
  const deltaLon = 360 * distance / (Math.PI * r * 2);
  const resMaxLon = Math.ceil((lon + deltaLon) / deltaLon) * deltaLon;
  const resMinLon = Math.floor((lon - deltaLon) / deltaLon) * deltaLon;

  return {
    //latMin: resMinLat < -90 ? -90 : resMinLat,
    //latMax: resMaxLat > 90 ? 90 : resMaxLat,
    //lonMin: resMinLon < -180 ? -180 : resMinLon,
    //lonMax: resMaxLon > 180 ? 180 : resMaxLon
    latMin:    resMinLat,
    latMax:    resMaxLat,
    lonMin:    resMinLon,
    lonMax:    resMaxLon,
    latIgnore: deltaLat >= 90,
    lonIgnore: deltaLon >= 180
  };
}

function getDistanceFromLatLonInKm(lat1, lon1, lat2, lon2) {
  var R = 6371; // Radius of the earth in km
  var dLat = deg2rad(lat2 - lat1);  // deg2rad below
  var dLon = deg2rad(lon2 - lon1);
  var a =
        Math.sin(dLat / 2) * Math.sin(dLat / 2) +
        Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) *
        Math.sin(dLon / 2) * Math.sin(dLon / 2)
    ;
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  var d = R * c; // Distance in km
  return d;
}

function deg2rad(deg) {
  return deg * (Math.PI / 180)
}

//console.log(180 * 100 * 360 * 100 * 3)
var _ = require('lodash');

var testResult = {};
_.each(_.range(1, 11), function (v) {
  testResult[v] = {
    latMin: 90,
    latMax: -90,
    lonMin: 180,
    lonMax: -180
  };
});

function updateError(key, lat1, lon1) {
  var tr = testResult[key];
  if (!tr) {
    console.error(key);
    process.exit(1);
  }
  tr.latMin = Math.min(tr.latMin, lat1);
  tr.latMax = Math.max(tr.latMax, lat1);
  tr.lonMax = Math.max(tr.lonMax, lon1);
  tr.lonMin = Math.min(tr.lonMin, lon1);
}

var maxDistance = 0;

var latStart = 90, latStep = 0.5, latHole = 0;
var lonStart = 180, lonStep = 0.5;
var distStart = 5, distStep = 5, distEnd = 10;
var len = ((latStart - latHole) * 2 / latStep) * (lonStart * 2 / lonStep) * ((distEnd - distStart) / distStep);
//var len = (latStart * 2 / latStep) * (lonStart * 2 / lonStep) * ((distEnd - distStart)/ distStep);

var passedOver = 0;
var flag1 = false;
var flag2 = false;

_.each(_.union(_.range(-latStart, -latHole, latStep), _.range(latHole, latStart + latStep, latStep)), function (lat) {
//_.each(_.range(-latStart, latStart + latStep, latStep), function (lat) {
  _.each(_.range(-lonStart, lonStart + lonStep, lonStep), function (lon) {
    _.each(_.range(distStart, distEnd, distStep), function (distance) {
      var distanceTest = distance;
      var cb = function () {
        var res = approximateDistance(distance, lat, lon);

        if (res.latIgnore) {
          //console.log('aaalat', distance);
          flag1 = true;
          return;
        }
        if (res.lonIgnore) {
          //console.log('aaalon', distance);
          flag2 = true;
          return;
        }
        updateError(9, res.latMin, res.lonMin);
        updateError(10, res.latMax, res.lonMax);
//console.log(lat, lon, distance)
//console.log(res)
        var dist = getDistanceFromLatLonInKm(lat, lon, res.latMax, res.lonMax);
        //console.log(dist)
        maxDistance = Math.max(maxDistance, dist);
        if (dist < distanceTest) {
          console.error("**t1**", Math.round(dist), lat, lon);
          updateError(1, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, res.latMax, res.lonMin);
        maxDistance = Math.max(maxDistance, dist);
        //console.log(dist)
        if (dist < distanceTest) {
          console.error("**t2**", Math.round(dist), lat, lon);
          updateError(2, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, res.latMin, res.lonMax);
        maxDistance = Math.max(maxDistance, dist);
        //console.log(dist)
        if (dist < distanceTest) {
          console.error("**t3**", Math.round(dist), lat, lon);
          updateError(3, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, res.latMin, res.lonMin);
        maxDistance = Math.max(maxDistance, dist);
        //console.log(dist)
        if (dist < distanceTest) {
          console.error("**t4**", Math.round(dist), lat, lon);
          updateError(4, lat, lon);
        }

        dist = getDistanceFromLatLonInKm(lat, lon, 90, 180);
        if (dist < distanceTest) {
          console.log("**t5**", Math.round(dist), lat, lon);
          updateError(5, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, 90, -180);
        if (dist < distanceTest) {
          console.log("**t6**", Math.round(dist), lat, lon);
          updateError(6, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, -90, 180);
        if (dist < distanceTest) {
          console.log("**t7**", Math.round(dist), lat, lon);
          updateError(7, lat, lon);
        }
        dist = getDistanceFromLatLonInKm(lat, lon, -90, -180);
        if (dist < distanceTest) {
          console.log("**t8**", Math.round(dist), lat, lon);
          updateError(8, lat, lon);
        }
      };
      cb();
      if (passedOver++ % 1000000 === 0) {

        console.log(100 * passedOver / len, "%   (", passedOver, len, ")");
        console.log(testResult);
      }

      //process.nextTick(cb);
    });
  });
});

console.log("\n  DONE", testResult, flag1, flag2, maxDistance);