const mysql = require('../utils/mysql_db')
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const numbers = require('../utils/numbers')
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async function Locating() {
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try {
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//首先获取已计算生成的非法电台目录
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let sql = `SELECT id,frequency,confirm FROM fm_t_illegal_radio;`;
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let result = await mysql.query(sql);
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let map_illegal_radio = {};
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for (let i = 0; i < result.length; i++) {
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map_illegal_radio[result[i].frequency] = result[i];
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}
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//获取扫描记录中所有非法电台记录 用以计算
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sql = `
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SELECT frequency, signal_strength, lon, lat, max(upload_time) AS upload_time
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FROM fm_t_scan_record a
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LEFT JOIN fm_t_task_record b ON a.task_record_id = b.id
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WHERE result <> '0' AND result <> '1' AND signal_strength IS NOT NULL AND lon IS NOT NULL AND lat IS NOT NULL
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GROUP BY frequency, device_lgid ;`;
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result = await mysql.query(sql);
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let map_data = {};
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for (let i = 0; i < result.length; i++) {
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if (map_data[result[i].frequency]) {
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map_data[result[i].frequency].push(result[i]);
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} else {
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map_data[result[i].frequency] = [result[i]];
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}
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}
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//依次计算每个非法电台的位置
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for (let freq in map_data) {
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if (map_illegal_radio[freq] && map_illegal_radio[freq].confirm == "已确认") {
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continue; //如果电台信息已经经过确认，则不再计算
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}
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let data = map_data[freq];
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let xy = [];
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let dis = [];
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for (let i = 0; i < data.length; i++) {
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xy.push([data[i].lon, data[i].lat]);
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dis.push(getDistanceByRSS(data[i].signal_strength)); //计算距离
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}
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let location = equationSolving(xy, dis); //求解坐标
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if (!location) {
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continue;
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}
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//保存计算结果到数据库
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if (map_illegal_radio[freq]) {
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sql = `UPDATE fm_t_illegal_radio
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SET lon=${location[0][0]},
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lat=${location[1][0]},
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time=NOW()
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WHERE id=${map_illegal_radio[freq].id};`;
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} else {
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sql = `INSERT INTO fm_t_illegal_radio (frequency,lon,lat,confirm,time,detail)
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VALUES(${freq},
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${location[0][0]},
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${location[1][0]},
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'待确认',
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NOW(),
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'平台计算');`;
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}
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result = await mysql.query(sql);
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}
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return true;
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} catch (err) {
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return false;
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}
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}
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//通过接收信号强度近似计算电台距离 便于计算返回值单位转为 度
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function getDistanceByRSS(rss) {
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let dis = -0.0236 * rss - 2.0394; //距离近似计算公式
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return dis > 0 ? dis : 0;
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}
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//求解距离方程组 得到电台坐标
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//xy为n x 2 的矩阵，表示n个已知点的坐标
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//dis为n个已知点到未知点的距离
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function equationSolving(xy, dis) {
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try {
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if (dis.length == 1) {
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let theta = Math.random() * Math.PI;
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return [
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[xy[0][0] + dis * Math.cos(theta)],
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[xy[0][1] + dis * Math.sin(theta)]
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];
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} else if (dis.length == 2) {
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//仅粗略计算，直接返回 中点 ------ 待改进
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return [
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[0.5 * (xy[0][0] + xy[1][0])],
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[0.5 * (xy[0][1] + xy[1][1])]
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];
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} else {
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let n = dis.length;
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let A = [];
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let b = [];
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const c = dis[n - 1] * dis[n - 1] - xy[n - 1][0] * xy[n - 1][0] - xy[n - 1][1] * xy[n - 1][1];
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for (let i = 0; i < n - 1; i++) {
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A.push([2 * (xy[i][0] - xy[n - 1][0]), 2 * (xy[i][1] - xy[n - 1][1])]);
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b.push([xy[i][0] * xy[i][0] + xy[i][1] * xy[i][1] - dis[i] * dis[i] + c]);
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}
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let AT = [
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numbers.matrix.getCol(A, 0),
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numbers.matrix.getCol(A, 1)
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];
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let X = numbers.matrix.multiply(
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numbers.matrix.multiply(
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numbers.matrix.inverse(numbers.matrix.multiply(AT, A)),
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AT),
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b);
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return X;
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}
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} catch (err) {
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return null;
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}
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}
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Locating();
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