mirror of https://github.com/espruino/BangleApps
gipy : compute distances
frederic wagner
parent
a1705964c2
commit
81226a34d6
169
apps/gipy/app.js
169
apps/gipy/app.js
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@ -10,36 +10,48 @@
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var lat = null;
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var lon = null;
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var refresh_needed = false;
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class Path {
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constructor(filename) {
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let buffer = require("Storage").readArrayBuffer(filename);
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this.points = Float64Array(buffer);
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let total_distance = 0.0;
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this.on_segments(function (p1, p2, i) {
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total_distance += p1.distance(p2);
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}, 0, this.len-1);
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this.total_distance = total_distance;
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}
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// start is index of first wanted segment
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// end is 1 after index of last wanted segment
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on_segments(op, start, end) {
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let previous_point = null;
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for(let i = start ; i < end + 1 ; i++) {
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let point = new Point(this.points[2*i], this.points[2*i+1]);
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if (previous_point !== null) {
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op(previous_point, point, i);
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}
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previous_point = point;
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}
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}
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point(index) {
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let lon = this.points[2*index];
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let lat = this.points[2*index+1];
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return new Point(lon, lat);
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}
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// return index of segment which is nearest from point
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nearest_segment(point, start, end) {
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let previous_point = null;
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let min_index = 0;
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let min_distance = Number.MAX_VALUE;
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for(let i = Math.max(0, start) ; i < Math.min(this.len, end) ; i++) {
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let current_point = this.point(i);
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if (previous_point !== null) {
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let distance = point.distance_to_segment(previous_point, current_point);
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this.on_segments(function (p1, p2, i) {
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let distance = point.fake_distance_to_segment(p1, p2);
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if (distance <= min_distance) {
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min_distance = distance;
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min_index = i-1;
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}
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}
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previous_point = current_point;
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}
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}, start, end);
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return min_index;
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}
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get len() {
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@ -77,9 +89,24 @@ class Point {
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return this.lon * other_point.lon + this.lat * other_point.lat;
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}
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distance(other_point) {
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//see https://www.movable-type.co.uk/scripts/latlong.html
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const R = 6371e3; // metres
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const phi1 = this.lat * Math.PI/180;
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const phi2 = other_point.lat * Math.PI/180;
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const deltaphi = (other_point.lat-this.lat) * Math.PI/180;
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const deltalambda = (other_point.lon-this.lon) * Math.PI/180;
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const a = Math.sin(deltaphi/2) * Math.sin(deltaphi/2) +
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Math.cos(phi1) * Math.cos(phi2) *
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Math.sin(deltalambda/2) * Math.sin(deltalambda/2);
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const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
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return R * c; // in metres
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}
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fake_distance(other_point) {
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return Math.sqrt(this.length_squared(other_point));
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}
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distance_to_segment(v, w) {
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fake_distance_to_segment(v, w) {
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// from : https://stackoverflow.com/questions/849211/shortest-distance-between-a-point-and-a-line-segment
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// Return minimum distance between line segment vw and point p
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let l2 = v.length_squared(w); // i.e. |w-v|^2 - avoid a sqrt
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@ -87,96 +114,86 @@ class Point {
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return this.distance(v); // v == w case
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}
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// Consider the line extending the segment, parameterized as v + t (w - v).
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// We find projection of point p onto the line.
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// We find projection of point p onto the line.
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// It falls where t = [(p-v) . (w-v)] / |w-v|^2
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// We clamp t from [0,1] to handle points outside the segment vw.
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let t = Math.max(0, Math.min(1, (this.minus(v)).dot(w.minus(v)) / l2));
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let projection = v.plus((w.minus(v)).times(t)); // Projection falls on the segment
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return this.distance(projection);
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return this.fake_distance(projection);
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}
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}
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function display(path) {
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if (!refresh_needed) {
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return;
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}
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refresh_needed = false;
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g.clear();
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g.setColor(g.theme.fg);
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// let next_segment = path.nearest_segment(new Point(lon, lat), current_segment-2, current_segment+3);
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current_segment = path.nearest_segment(new Point(lon, lat), 0, path.len);
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let previous_point = null;
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current_segment = path.nearest_segment(new Point(lon, lat), 0, path.len-1);
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let start = Math.max(current_segment - 5, 0);
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let end = Math.min(current_segment + 7, path.len);
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for (let i=start ; i < end ; i++) {
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let point = path.point(i);
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let px = point.screen_x();
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let py = point.screen_y();
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if (previous_point !== null) {
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if (i == current_segment + 1) {
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g.setColor(0.0, 1.0, 0.0);
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} else {
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g.setColor(1.0, 0.0, 0.0);
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}
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g.drawLine(
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previous_point.screen_x(),
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previous_point.screen_y(),
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px,
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py
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);
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let end = Math.min(current_segment + 7, path.len-1);
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path.on_segments(function(p1, p2, i) {
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let px = p2.screen_x();
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let py = p2.screen_y();
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if (i == current_segment + 1) {
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g.setColor(0.0, 1.0, 0.0);
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} else {
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g.setColor(1.0, 0.0, 0.0);
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}
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g.setColor(g.theme.fg2);
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g.fillCircle(px, py, 4);
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g.drawLine(
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p1.screen_x(),
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p1.screen_y(),
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px,
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py
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);
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g.setColor(g.theme.fg);
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g.fillCircle(px, py, 4);
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g.setColor(g.theme.bg);
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g.fillCircle(px, py, 3);
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previous_point = point;
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}
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}, 0, path.len-1);
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g.setColor(g.theme.fgH);
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g.fillCircle(172/2, 172/2, 5);
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g.setFont("6x8:2").drawString(("distance "+(Math.round(path.total_distance/100)/10))+" km",0,30);
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Bangle.drawWidgets();
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}
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Bangle.loadWidgets();
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let path = new Path("test.gpc");
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var current_segment = path.nearest_segment(new Point(lon, lat), 0, Number.MAX_VALUE);
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var current_segment = path.nearest_segment(new Point(lon, lat), 0, path.len-1);
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// let fake_gps_point = 0.0;
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// function simulate_gps(path) {
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// let point_index = Math.floor(fake_gps_point);
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// if (point_index >= path.len) {
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// return;
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// }
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// let p1 = path.point(point_index);
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// let p2 = path.point(point_index+1);
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// let alpha = fake_gps_point - point_index;
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// lon = (1-alpha)*p1.lon + alpha*p2.lon;
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// lat = (1-alpha)*p1.lat + alpha*p2.lat;
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// fake_gps_point += 0.2;
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// display(path);
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// }
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// setInterval(simulate_gps, 500, path);
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function set_coordinates(data) {
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let old_lat = lat;
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if (!isNaN(data.lat)) {
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lat = data.lat;
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}
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let old_lon = lon;
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if (!isNaN(data.lon)) {
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lon = data.lon;
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}
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if ((old_lat != lat)||(old_lon != lon)) {
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refresh_needed = true;
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let fake_gps_point = 0.0;
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function simulate_gps(path) {
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let point_index = Math.floor(fake_gps_point);
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if (point_index >= path.len) {
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return;
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}
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let p1 = path.point(point_index);
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let p2 = path.point(point_index+1);
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let alpha = fake_gps_point - point_index;
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lon = (1-alpha)*p1.lon + alpha*p2.lon;
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lat = (1-alpha)*p1.lat + alpha*p2.lat;
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fake_gps_point += 0.2;
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display(path);
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}
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Bangle.setGPSPower(true, "gipy");
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Bangle.on('GPS', set_coordinates);
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setInterval(simulate_gps, 500, path);
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setInterval(display, 1000, path);
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// function set_coordinates(data) {
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// let old_lat = lat;
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// if (!isNaN(data.lat)) {
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// lat = data.lat;
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// }
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// let old_lon = lon;
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// if (!isNaN(data.lon)) {
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// lon = data.lon;
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// }
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// if ((old_lat != lat)||(old_lon != lon)) {
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// display(path);
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// }
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// }
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// Bangle.setGPSPower(true, "gipy");
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// Bangle.on('GPS', set_coordinates);
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