Rotated points in mapbox are skewed

Rotated points in mapbox are skewed - javascript

I have a mapbox example where I do the following:1) setup a view with a pitch angle of 60 degrees2) map the canvas corner points to get the viewing frustrum as a trapezoid3) change the bearing by 30 degrees and get and draw the trapezoid again4) zoom out to see the trapezoids5) manually rotate the first trapezoid by 30 degrees6) draw the rotated trapezoid7) change the pitch to zero to look down at the imageWhen I do this, the manually rotated trapezoid (red in the image) does not match the one generated using the setBearing() call (purple in the image). It appears to be skewed improperly and I have been looking at the manual rotate code for 8 hours and cannot figure out why. Am I dealing with curvature of the earth rotated co-ordinate issues or? Can someone sort this out? Thanks!
mapboxgl.accessToken = 'pk.eyJ1IjoiZm1hY2RlZSIsImEiOiJjajJlNWMxenowNXU2MzNudmkzMndwaGI3In0.ALOYWlvpYXnlcH6sCR9MJg';
var map;
function addLayerToMap(name, points, color, width) {
map.addLayer({
"id": name,
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": points
}
}
},
"layout": {
"line-join": "round",
"line-cap": "round"
},
"paint": {
"line-color": color,
"line-width": width
}
});
}
function pointsRotate(points, cx, cy, angle){
var radians = (Math.PI / 180) * angle;
var cos = Math.cos(radians);
var sin = Math.sin(radians);
var newpoints = [];
function rotate(x, y) {
nx = (cos * (x - cx)) + (sin * (y - cy)) + cx,
ny = (cos * (y - cy)) + (-sin * (x - cx)) + cy;
return [nx, ny];
}
for(var i=0;i<points.length;i++) {
newpoints[i] = rotate(points[i][0],points[i][1]);
}
return(newpoints);
}
function convertTrapezoidToPath(trap) {
return([
[trap.Tl.lng, trap.Tl.lat], [trap.Tr.lng, trap.Tr.lat],
[trap.Br.lng, trap.Br.lat], [trap.Bl.lng, trap.Bl.lat],
[trap.Tl.lng, trap.Tl.lat] ]);
}
function getViewTrapezoid() {
var canvas = map.getCanvas();
var trap = {};
trap.Tl = map.unproject([0,0]);
trap.Tr = map.unproject([canvas.offsetWidth,0]);
trap.Br = map.unproject([canvas.offsetWidth,canvas.offsetHeight]);
trap.Bl = map.unproject([0,canvas.offsetHeight]);
return(trap);
}
map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.48610019683838, 37.82880236636284],
zoom: 17,
pitch: 60
});
map.on('load', function () {
// get the center and trapezoid of the zoomed in view
var center = map.getCenter();
var trapezoid = getViewTrapezoid();
// convert the view trapezoid to a path and add it to the view
var trapezoid_path = convertTrapezoidToPath(trapezoid);
addLayerToMap("viewTrapezoid",trapezoid_path,'#888',4);
// now rotate the bearing by 30 degrees to get a second view trapezoid
map.setBearing(30);
setTimeout(function() {
var trapezoid2 = getViewTrapezoid();
var trapezoid2_path = convertTrapezoidToPath(trapezoid2);
addLayerToMap("viewTrapezoid2",trapezoid2_path,'#f0f',2);
// return to a "top down" view and zoom out to show the trapezoids
map.setBearing(0);
map.setZoom(13.5);
setTimeout(function() {
map.flyTo({ pitch: 0 });
// rotate the original view trapezoid by 30 degrees and add it to the map
var newpath = pointsRotate(trapezoid_path,center.lng,center.lat,30);
addLayerToMap("rotatedTrapezoid",newpath,'#f00',2);
}, 500);
}, 500);
});
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.css' rel='stylesheet' />
<div id='map'></div>

Ok, so it turns out that because of longitude getting thinner as you approach the poles, you first need to convert all degree co-ordinates (lat and long) to Mercator co-ordinates that take into account the non-spherical nature of the earth. I've added two functions here that convert from lat lon to mercator and vice versa and put them into the code and the result is a trapezoid that is directly on top of the one provided using the setBearing() method. Problem solved!
mapboxgl.accessToken = 'pk.eyJ1IjoiZm1hY2RlZSIsImEiOiJjajJlNWMxenowNXU2MzNudmkzMndwaGI3In0.ALOYWlvpYXnlcH6sCR9MJg';
var map;
function addLayerToMap(name, points, color, width) {
map.addLayer({
"id": name,
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": points
}
}
},
"layout": {
"line-join": "round",
"line-cap": "round"
},
"paint": {
"line-color": color,
"line-width": width
}
});
}
function pointsRotate(points, cx, cy, angle){
var radians = (Math.PI / 180) * angle;
var cos = Math.cos(radians);
var sin = Math.sin(radians);
var newpoints = [];
function rotate(x, y) {
nx = (cos * (x - cx)) + (sin * (y - cy)) + cx,
ny = (cos * (y - cy)) + (-sin * (x - cx)) + cy;
return [nx, ny];
}
for(var i=0;i<points.length;i++) {
newpoints[i] = rotate(points[i][0],points[i][1]);
}
return(newpoints);
}
function convertTrapezoidToPath(trap) {
return([
[trap.Tl.lng, trap.Tl.lat], [trap.Tr.lng, trap.Tr.lat],
[trap.Br.lng, trap.Br.lat], [trap.Bl.lng, trap.Bl.lat],
[trap.Tl.lng, trap.Tl.lat] ]);
}
function getViewTrapezoid() {
var canvas = map.getCanvas();
var trap = {};
trap.Tl = map.unproject([0,0]);
trap.Tr = map.unproject([canvas.offsetWidth,0]);
trap.Br = map.unproject([canvas.offsetWidth,canvas.offsetHeight]);
trap.Bl = map.unproject([0,canvas.offsetHeight]);
return(trap);
}
function Mercator2ll(mercX, mercY) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var lon = mercX / shift * 180.0;
var lat = mercY / shift * 180.0;
lat = 180 / Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180.0)) - Math.PI / 2.0);
return [ lon, lat ];
}
function ll2Mercator(lon, lat) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var x = lon * shift / 180;
var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
y = y * shift / 180;
return [ x, y ];
}
function convertDegrees2Meters(points) {
var newpoints = [];
for(var i=0;i<points.length;i++) {
newpoints[i] = ll2Mercator( points[i][0], points[i][1] );
}
return newpoints;
}
function convertMeters2Degrees(points) {
var newpoints = [];
for(var i=0;i<points.length;i++) {
newpoints[i] = Mercator2ll( points[i][0], points[i][1] );;
}
return newpoints;
}
map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.48610019683838, 37.82880236636284],
zoom: 17,
pitch: 60
});
map.on('load', function () {
// get the center and trapezoid of the zoomed in view
var center = map.getCenter();
var trapezoid = getViewTrapezoid();
var center_meters = ll2Mercator(center.lng,center.lat);
// convert the view trapezoid to a path and add it to the view
var trapezoid_path = convertTrapezoidToPath(trapezoid);
addLayerToMap("viewTrapezoid",trapezoid_path,'#888',4);
// now rotate the bearing by 30 degrees to get a second view trapezoid
map.setBearing(30);
setTimeout(function() {
var trapezoid2 = getViewTrapezoid();
var trapezoid2_path = convertTrapezoidToPath(trapezoid2);
addLayerToMap("viewTrapezoid2",trapezoid2_path,'#f0f',2);
// return to a "top down" view and zoom out to show the trapezoids
map.setBearing(0);
map.setZoom(13.5);
setTimeout(function() {
map.flyTo({ pitch: 0 });
// rotate the original view trapezoid by 30 degrees and add it to the map
var tpath_meters = convertDegrees2Meters(trapezoid_path);
var newpath_meters = pointsRotate(tpath_meters,center_meters[0],center_meters[1],30);
var newpath = convertMeters2Degrees(newpath_meters);
addLayerToMap("rotatedTrapezoid",newpath,'#f00',2);
}, 500);
}, 500);
});
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.css' rel='stylesheet' />
<div id='map'></div>

Related

Show fixed 100 m x 100 m grid on lowest zoom level

I am using leaflet with openstreetmap to create a fixed grid on top of the world map that consists of 100m x 100m tiles. Basically, I am creating a turn-based game, where a player should be able to click on a certain tile, which then reveals a context menu. The server is going to know that the player has opened the tile for a certain place.
I tried the following:
<!DOCTYPE html>
<html>
<head>
<title>GridLayer Test</title>
<meta charset="utf-8" />
<link rel="stylesheet" href="https://unpkg.com/leaflet#1.0.1/dist/leaflet.css" />
<style>
body {
padding: 0;
margin: 0;
}
html,
body,
#map {
height: 100%;
width: 100%;
}
</style>
</head>
<body>
<div id="map"></div>
<script src="https://unpkg.com/leaflet#1.0.1/dist/leaflet.js"></script>
<script>
var map = new L.Map('map', { center: [10, 0], zoom: 2 });
var tiles = new L.GridLayer();
tiles.createTile = function (coords) {
var tile = L.DomUtil.create('canvas', 'leaflet-tile');
var ctx = tile.getContext('2d');
var size = this.getTileSize()
tile.width = size.x
tile.height = size.y
// calculate projection coordinates of top left tile pixel
var nwPoint = coords.scaleBy(size)
// calculate geographic coordinates of top left tile pixel
var nw = map.unproject(nwPoint, coords.z)
ctx.fillStyle = 'white';
ctx.fillRect(0, 0, size.x, 50);
ctx.fillStyle = 'black';
ctx.fillText('x: ' + coords.x + ', y: ' + coords.y + ', zoom: ' + coords.z, 20, 20);
ctx.fillText('lat: ' + nw.lat + ', lon: ' + nw.lng, 20, 40);
ctx.strokeStyle = 'red';
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(size.x - 1, 0);
ctx.lineTo(size.x - 1, size.y - 1);
ctx.lineTo(0, size.y - 1);
ctx.closePath();
ctx.stroke();
return tile;
}
L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
attribution: 'Map data © OpenStreetMap',
minNativeZoom: 1,
maxNativeZoom: 1,
}).addTo(map)
tiles.addTo(map)
</script>
</body>
</html>
As you can see the grid changed when I zoom in or out, even though I used minNativeZoom. However, I would like to have the grid fixed and 100m x 100m wide.
I also tried to only return tile when zoomLevel = 18. This does not work.
Any suggestions what I am doing wrong?
I appreciate your replies!

You can draw a grid with the following createTile implementation:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>GridLayer Test</title>
<link rel="stylesheet" href="https://unpkg.com/leaflet#1.0.1/dist/leaflet.css" />
<style>
body {
padding: 0;
margin: 0;
}
html,
body,
#map {
height: 100%;
width: 100%;
}
</style>
</head>
<body>
<div id="map"></div>
<script src="https://unpkg.com/leaflet#1.0.1/dist/leaflet.js"></script>
<script>
const numTilesX = 2 ** 17
const numTilesY = 2 ** 17
class TileNumber {
constructor(x, y) {
this.x = x;
this.y = y;
}
equals(other) {
return this.x === other.x && this.y === other.y;
}
}
let coloredTiles = [
new TileNumber(70435, 45249),
new TileNumber(70434, 45248),
new TileNumber(70441, 45245)
]
function latLngToTileNumber(latLng) {
const lngDegrees = latLng.lng;
const latRadians = latLng.lat * (Math.PI/180);
return new L.Point(
numTilesX * ((lngDegrees + 180) / 360),
numTilesY * (1 - Math.log(Math.tan(latRadians) + 1 / Math.cos(latRadians)) / Math.PI) / 2
);
}
const map = new L.Map('map', {center: [48.5748229, 13.4609744], zoom: 16, maxZoom: 19});
L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
attribution: 'Map data © OpenStreetMap', maxZoom: 19
}).addTo(map)
const tiles = new L.GridLayer({minZoom: 12});
tiles.createTile = function (coords) {
const tile = L.DomUtil.create('canvas', 'leaflet-tile');
const ctx = tile.getContext('2d');
const size = this.getTileSize();
tile.width = size.x
tile.height = size.y
// calculate projection coordinates of top left tile pixel
const nwPoint = coords.scaleBy(size);
// calculate geographic coordinates of top left tile pixel
const nw = map.unproject(nwPoint, coords.z);
// calculate fraction tile number at top left point
const nwTile = latLngToTileNumber(nw, Math.floor)
// calculate projection coordinates of bottom right tile pixel
const sePoint = new L.Point(nwPoint.x + size.x - 1, nwPoint.y + size.y - 1)
// calculate geographic coordinates of bottom right tile pixel
const se = map.unproject(sePoint, coords.z);
// calculate fractional tile number at bottom right point
const seTile = latLngToTileNumber(se, Math.ceil)
const minTileX = nwTile.x
const maxTileX = seTile.x
const minTileY = nwTile.y
const maxTileY = seTile.y
for (let x = Math.ceil(minTileX) - 1; x <= Math.floor(maxTileX) + 1; x++) {
for (let y = Math.ceil(minTileY) - 1; y <= Math.floor(maxTileY) + 1; y++) {
let tile = new TileNumber(x, y)
const xMinPixel = Math.round(size.x * (x - minTileX) / (maxTileX - minTileX));
const xMaxPixel = Math.round(size.x * (x + 1 - minTileX) / (maxTileX - minTileX));
const yMinPixel = Math.round(size.y * (y - minTileY) / (maxTileY - minTileY));
const yMaxPixel = Math.round(size.y * (y + 1 - minTileY) / (maxTileY - minTileY));
// fill the rectangle with a color
ctx.fillStyle = coloredTiles.some(t => t.equals(tile))
? 'rgba(0, 0, 255, 0.3)'
: 'rgba(255, 255, 255, 0)';
ctx.fillRect(xMinPixel, yMinPixel, xMaxPixel - xMinPixel, yMaxPixel - yMinPixel);
if (coords.z >= 16) {
// draw the white rectangle and text at the top of the cell
ctx.fillStyle = 'white';
ctx.fillRect(xMinPixel, yMinPixel, xMaxPixel - xMinPixel, 28);
ctx.fillStyle = 'black';
ctx.font = "15px Arial"
ctx.fillText(tile.x + "," + tile.y, xMinPixel + 10, yMinPixel + 20, xMaxPixel - xMinPixel);
}
if (coords.z >= 13) {
// draw a border
ctx.strokeStyle = 'black';
ctx.strokeRect(xMinPixel, yMinPixel, xMaxPixel - xMinPixel, yMaxPixel - yMinPixel);
}
}
}
return tile;
}
tiles.addTo(map);
map.on('click', e => {
const fractionalTileNumber = latLngToTileNumber(e.latlng);
const tileNumber = new TileNumber(Math.floor(fractionalTileNumber.x), Math.floor(fractionalTileNumber.y));
console.log("Tile " + tileNumber.x + " " + tileNumber.y + " clicked");
if (coloredTiles.some(t => t.equals(tileNumber))) {
coloredTiles = coloredTiles.filter(t => !t.equals(tileNumber));
} else {
coloredTiles.push(tileNumber);
}
tiles.redraw();
});
</script>
</body>
</html>
Some caveats:
Because the earth isn't flat, it's not really possible to cleanly cover it with a grid of rectangles. So I did the closest thing to it by drawing grid boundaries along latitude and longitude lines. As a result, the tiles will get larger (cover more square meters) towards the equator and smaller towards the poles.
Each grid cell has an unique TileNumber (x and y coordinate, starting at 0,0 in the northwestern corner).
To demonstrate clicking on the map, I'm writing the TileNumber of the to the log and toggle the tile's colored/uncolored state. Of course, this could be replaced with any other functionality imaginable, including communication with a server.
As this snippet includes the ability to color the grid cells based on their TileNumber (stored in an array), I've provided this as an answer to your question about coloring grid tiles as well.

Google Maps V3: Hexagon grid - Error with setWindow

I am making hexagon grid for my game based on Google Map v3 and got a problem.
After I click in one hexagon are showing differents values, not one the same as for marker inside of the all hexagon.
The right value is showing just in the left down corner of quarter hexagon.
The value of coord_slug is making based on coordinates lat, lng.
What I have to do hexagon and marker values being the same ?
In this way 55.3,14.8 for upper and 55.25,1485 for down hexagon.
I need those values in a game for downloading dates from database.
The part responsible for displaying the value:
function set_window(event) {
// Set Parameters
var lat = event.latLng.lat();
var lng = event.latLng.lng();
var coord_slug = (Math.round(lat * 20) / 20) + ',' + (Math.round(lng * 20) / 20);
alert(coord_slug);
}
The working part of the script here:
function round_down(n) {
if (n > 0) {
return Math.ceil(n / 0.05) * 0.05;
} else {
return 0;
}
}
var map;
var pointCount = 0;
var locations = [];
var gridWidth = 3660; // hex tile size in meters
var bounds;
var places = [
[55.3, 14.8],
[55.25, 14.85],
]
var SQRT3 = 1.73205080756887729352744634150587236;
$(document).ready(function(){
bounds = new google.maps.LatLngBounds();
map = new google.maps.Map(document.getElementById("map_canvas"), {center: {lat: 55.27, lng: 14.8}, zoom: 10});
// Adding a marker just so we can visualize where the actual data points are.
// In the end, we want to see the hex tile that contain them
places.forEach(function(place, p){
latlng = new google.maps.LatLng({lat: place[0], lng: place[1]});
marker = new google.maps.Marker({
position: latlng,
map: map})
marker.addListener('click', set_window);
// Fitting to bounds so the map is zoomed to the right place
bounds.extend(latlng);
});
// Now, we draw our hexagons! (or try to)
locations = makeBins(places);
locations.forEach(function(place, p){
drawHorizontalHexagon(map, place, gridWidth);
})
});
function drawHorizontalHexagon(map, position, radius){
var coordinates = [];
for(var angle= 0;angle < 360; angle+=60) {
coordinates.push(google.maps.geometry.spherical.computeOffset(position, radius, angle));
}
// Construct the polygon.
var polygon = new google.maps.Polygon({
paths: coordinates,
position: position,
strokeColor: '#FF0000',
strokeOpacity: 0.8,
strokeWeight: 2,
fillColor: '#FF0000',
fillOpacity: 0.35,
geodesic: true
});
polygon.setMap(map);
polygon.addListener('click', set_window);
}
// Below is my attempt at porting binner.py to Javascript.
// Source: https://github.com/coryfoo/hexbins/blob/master/hexbin/binner.py
function distance(x1, y1, x2, y2){
console.log(x1, y1, x2, y2);
result = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
console.log("Distance: ", result);
return
}
function nearestCenterPoint(value, scale){
div = value / (scale/2);
console.log("div", div);
mod = value % (scale/2);
console.log("mod", mod);
if(div % 2 == 1){
increment = 1;
} else{
increment = 0;
}
rounded = scale / 2 * (div + increment);
if(div % 2 === 0){
increment = 1;
} else{
increment = 0;
}
rounded_scaled = scale / 2 * (div + increment);
result = [rounded, rounded_scaled]
console.log("nearest centerpoint to", value, result);
return result;
}
function makeBins(data){
bins = [];
data.forEach(function(place, p){
x = place[0];
y = place[1];
console.log("Original location:", x, y);
px_nearest = nearestCenterPoint(x, gridWidth);
py_nearest = nearestCenterPoint(y, gridWidth * SQRT3);
z1 = distance(x, y, px_nearest[0], py_nearest[0]);
z2 = distance(x, y, px_nearest[1], py_nearest[1]);
if(z1 > z2){
bin = new google.maps.LatLng({lat: px_nearest[0], lng: py_nearest[0]});
console.log("Final location:", px_nearest[0], py_nearest[0]);
} else {
bin = new google.maps.LatLng({lat: px_nearest[1], lng: py_nearest[1]});
console.log("Final location:", px_nearest[1], py_nearest[1]);
}
bins.push(bin);
})
return bins;
}
function set_window(event) {
// Set Parameters
var lat = event.latLng.lat();
var lng = event.latLng.lng();
var coord_slug = (Math.round(lat * 20) / 20) + ',' + (Math.round(lng * 20) / 20);
alert(coord_slug);
}
<html>
<head>
<script data-require="jquery#*" data-semver="2.2.0" src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.0/jquery.min.js"></script>
<script data-require="bootstrap#*" data-semver="3.3.6" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link data-require="bootstrap-css#3.3.6" data-semver="3.3.6" rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.css" />
<link rel="stylesheet" href="style.css" />
<script src="script.js"></script>
<script src="https://maps.googleapis.com/maps/api/js?libraries=geometry"></script>
</head>
<body>
<div id="map_canvas" style="width:100%; height:80vh;">
</div>
</body>
</html>
Additional link:
The working part of the script in Plunger

You are setting a position attribute to your Polygons, which seems to be what you want to display...
So you can replace the following
polygon.addListener('click', set_window);
By this:
polygon.addListener('click', function() {
var polyPosition = this.position.lat() + ', ' + this.position.lng();
alert(polyPosition);
});

mapbox-gl-js: Adjust visible area & bearing to a given line, for a given pitch

I'm trying to optimize a Mapbox view for long-distance hiking trails, like the Appalachian Trail or the Pacific Crest Trail. Here's an example, which I've oriented by hand, showing the Senda Pirenáica in Spain:
The area of interest, the viewport, and the pitch are given. I need to find the correct center, bearing, and zoom.
The map.fitBounds method doesn't help me here because it assumes pitch=0 and bearing=0.
I've done some poking around and this seems to be a variation of the smallest surrounding rectangle problem, but I'm stuck on a couple of additional complications:
How do I account for the distorting effect of pitch?
How do I optimize for the aspect ratio of the viewport? Note that taking the viewport narrower or wider would change the bearing of the best solution:
FWIW I'm also using turf-js, which helps me get the convex hull for the line.

This solution results in the path displayed at the correct bearing with a magenta trapezoid outline showing the target "tightest trapezoid" to show the results of the calculations. The extra line coming from the top corner shows where the map.center() value is located.
The approach is as follows:
render the path to the map using the "fitbounds" technique to get an approximate zoom level for the "north up and pitch=0" situation
rotate the pitch to the desired angle
grab the trapezoid from the canvas
This result would look like this:
After this, we want to rotate that trapezoid around the path and find the tightest fit of the trapezoid to the points. In order to test for the tightest fit it is easier to rotate the path rather than the trapezoid so I have taken that approach here. I haven't implemented a "convex hull" on the path to minimize the number of points to rotate but that is something that can be added as an optimization step.
To get the tightest fit, the first step is to move the map.center() so that the path is at the "back" of the view. This is where the most space is in the frustum so it will be easy to manipulate it there:
Next, we measure the distance between the angled trapezoid walls and each point in the path, saving the closest points on both the left and right sides. We then center the path in the view by translating the view horizontally based on these distances, and then scale the view to eliminate that space on both sides as shown by the green trapezoid below:
The scale used to get this "tightest fit" gives us our ranking for whether this is the best view of the path. However, this view may not be the best visually since we pushed the path to the back of the view to determine the ranking. Instead, we now adjust the view to place the path in the vertical center of the view, and scale the view triangle larger accordingly. This gives us the magenta colored "final" view desired:
Finally, this process is done for every degree and the minimum scale value determines the winning bearing, and we take the associated scale and center position from there.
mapboxgl.accessToken = 'pk.eyJ1IjoiZm1hY2RlZSIsImEiOiJjajJlNWMxenowNXU2MzNudmkzMndwaGI3In0.ALOYWlvpYXnlcH6sCR9MJg';
var map;
var myPath = [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
];
var myPath2 = [
[-122.48369693756104, 37.83381888486939],
[-122.49378204345702, 37.83368330777276]
];
function addLayerToMap(name, points, color, width) {
map.addLayer({
"id": name,
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": points
}
}
},
"layout": {
"line-join": "round",
"line-cap": "round"
},
"paint": {
"line-color": color,
"line-width": width
}
});
}
function Mercator2ll(mercX, mercY) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var lon = mercX / shift * 180.0;
var lat = mercY / shift * 180.0;
lat = 180 / Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180.0)) - Math.PI / 2.0);
return [ lon, lat ];
}
function ll2Mercator(lon, lat) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var x = lon * shift / 180;
var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
y = y * shift / 180;
return [ x, y ];
}
function convertLL2Mercator(points) {
var m_points = [];
for(var i=0;i<points.length;i++) {
m_points[i] = ll2Mercator( points[i][0], points[i][1] );
}
return m_points;
}
function convertMercator2LL(m_points) {
var points = [];
for(var i=0;i<m_points.length;i++) {
points[i] = Mercator2ll( m_points[i][0], m_points[i][1] );;
}
return points;
}
function pointsTranslate(points,xoff,yoff) {
var newpoints = [];
for(var i=0;i<points.length;i++) {
newpoints[i] = [ points[i][0] + xoff, points[i][1] + yoff ];
}
return(newpoints);
}
// note [0] elements are lng [1] are lat
function getBoundingBox(arr) {
var ne = [ arr[0][0] , arr[0][1] ];
var sw = [ arr[0][0] , arr[0][1] ];
for(var i=1;i<arr.length;i++) {
if(ne[0] < arr[i][0]) ne[0] = arr[i][0];
if(ne[1] < arr[i][1]) ne[1] = arr[i][1];
if(sw[0] > arr[i][0]) sw[0] = arr[i][0];
if(sw[1] > arr[i][1]) sw[1] = arr[i][1];
}
return( [ sw, ne ] );
}
function pointsRotate(points, cx, cy, angle){
var radians = angle * Math.PI / 180.0;
var cos = Math.cos(radians);
var sin = Math.sin(radians);
var newpoints = [];
function rotate(x, y) {
var nx = cx + (cos * (x - cx)) + (-sin * (y - cy));
var ny = cy + (cos * (y - cy)) + (sin * (x - cx));
return [nx, ny];
}
for(var i=0;i<points.length;i++) {
newpoints[i] = rotate(points[i][0],points[i][1]);
}
return(newpoints);
}
function convertTrapezoidToPath(trap) {
return([
[trap.Tl.lng, trap.Tl.lat], [trap.Tr.lng, trap.Tr.lat],
[trap.Br.lng, trap.Br.lat], [trap.Bl.lng, trap.Bl.lat],
[trap.Tl.lng, trap.Tl.lat] ]);
}
function getViewTrapezoid() {
var canvas = map.getCanvas();
var trap = {};
trap.Tl = map.unproject([0,0]);
trap.Tr = map.unproject([canvas.offsetWidth,0]);
trap.Br = map.unproject([canvas.offsetWidth,canvas.offsetHeight]);
trap.Bl = map.unproject([0,canvas.offsetHeight]);
return(trap);
}
function pointsScale(points,cx,cy, scale) {
var newpoints = []
for(var i=0;i<points.length;i++) {
newpoints[i] = [ cx + (points[i][0]-cx)*scale, cy + (points[i][1]-cy)*scale ];
}
return(newpoints);
}
var id = 1000;
function convertMercator2LLAndDraw(m_points, color, thickness) {
var newpoints = convertMercator2LL(m_points);
addLayerToMap("id"+id++, newpoints, color, thickness);
}
function pointsInTrapezoid(points,yt,yb,xtl,xtr,xbl,xbr) {
var str = "";
var xleft = xtr;
var xright = xtl;
var yh = yt-yb;
var sloperight = (xtr-xbr)/yh;
var slopeleft = (xbl-xtl)/yh;
var flag = true;
var leftdiff = xtr - xtl;
var rightdiff = xtl - xtr;
var tmp = [ [xtl, yt], [xtr, yt], [xbr,yb], [xbl,yb], [xtl,yt] ];
// convertMercator2LLAndDraw(tmp, '#ff0', 2);
function pointInTrapezoid(x,y) {
var xsloperight = xbr + sloperight * (y-yb);
var xslopeleft = xbl - slopeleft * (y-yb);
if((x - xsloperight) > rightdiff) {
rightdiff = x - xsloperight;
xright = x;
}
if((x - xslopeleft) < leftdiff) {
leftdiff = x - xslopeleft;
xleft = x;
}
if( (y<yb) || (y > yt) ) {
console.log("y issue");
}
else if(xsloperight < x) {
console.log("sloperight");
}
else if(xslopeleft > x) {
console.log("slopeleft");
}
else return(true);
return(false);
}
for(var i=0;i<points.length;i++) {
if(pointInTrapezoid(points[i][0],points[i][1])) {
str += "1";
}
else {
str += "0";
flag = false;
}
}
if(flag == false) console.log(str);
return({ leftdiff: leftdiff, rightdiff: rightdiff });
}
var viewcnt = 0;
function calculateView(trap, points, center) {
var bbox = getBoundingBox(points);
var bbox_height = Math.abs(bbox[0][1] - bbox[1][1]);
var view = {};
// move the view trapezoid so the path is at the far edge of the view
var viewTop = trap[0][1];
var pointsTop = bbox[1][1];
var yoff = -(viewTop - pointsTop);
var extents = pointsInTrapezoid(points,trap[0][1]+yoff,trap[3][1]+yoff,trap[0][0],trap[1][0],trap[3][0],trap[2][0]);
// center the view trapezoid horizontally around the path
var mid = (extents.leftdiff - extents.rightdiff) / 2;
var trap2 = pointsTranslate(trap,extents.leftdiff-mid,yoff);
view.cx = trap2[5][0];
view.cy = trap2[5][1];
var w = trap[1][0] - trap[0][0];
var h = trap[1][1] - trap[3][1];
// calculate the scale to fit the trapezoid to the path
view.scale = (w-mid*2)/w;
if(bbox_height > h*view.scale) {
// if the path is taller than the trapezoid then we need to make it larger
view.scale = bbox_height / h;
}
view.ranking = view.scale;
var trap3 = pointsScale(trap2,(trap2[0][0]+trap2[1][0])/2,trap2[0][1],view.scale);
w = trap3[1][0] - trap3[0][0];
h = trap3[1][1] - trap3[3][1];
view.cx = trap3[5][0];
view.cy = trap3[5][1];
// if the path is not as tall as the view then we should center it vertically for the best looking result
// this involves both a scale and a translate
if(h > bbox_height) {
var space = h - bbox_height;
var scale_mul = (h+space)/h;
view.scale = scale_mul * view.scale;
cy_offset = space/2;
trap3 = pointsScale(trap3,view.cx,view.cy,scale_mul);
trap3 = pointsTranslate(trap3,0,cy_offset);
view.cy = trap3[5][1];
}
return(view);
}
function thenCalculateOptimalView(path) {
var center = map.getCenter();
var trapezoid = getViewTrapezoid();
var trapezoid_path = convertTrapezoidToPath(trapezoid);
trapezoid_path[5] = [center.lng, center.lat];
var view = {};
//addLayerToMap("start", trapezoid_path, '#00F', 2);
// get the mercator versions of the points so that we can use them for rotations
var m_center = ll2Mercator(center.lng,center.lat);
var m_path = convertLL2Mercator(path);
var m_trapezoid_path = convertLL2Mercator(trapezoid_path);
// try all angles to see which fits best
for(var angle=0;angle<360;angle+=1) {
var m_newpoints = pointsRotate(m_path, m_center[0], m_center[1], angle);
var thisview = calculateView(m_trapezoid_path, m_newpoints, m_center);
if(!view.hasOwnProperty('ranking') || (view.ranking > thisview.ranking)) {
view.scale = thisview.scale;
view.cx = thisview.cx;
view.cy = thisview.cy;
view.angle = angle;
view.ranking = thisview.ranking;
}
}
// need the distance for the (cx, cy) from the current north up position
var cx_offset = view.cx - m_center[0];
var cy_offset = view.cy - m_center[1];
var rotated_offset = pointsRotate([[cx_offset,cy_offset]],0,0,-view.angle);
map.flyTo({ bearing: view.angle, speed:0.00001 });
// once bearing is set, adjust to tightest fit
waitForMapMoveCompletion(function () {
var center2 = map.getCenter();
var m_center2 = ll2Mercator(center2.lng,center2.lat);
m_center2[0] += rotated_offset[0][0];
m_center2[1] += rotated_offset[0][1];
var ll_center2 = Mercator2ll(m_center2[0],m_center2[1]);
map.easeTo({
center:[ll_center2[0],ll_center2[1]],
zoom : map.getZoom() });
console.log("bearing:"+view.angle+ " scale:"+view.scale+" center: ("+ll_center2[0]+","+ll_center2[1]+")");
// draw the tight fitting trapezoid for reference purposes
var m_trapR = pointsRotate(m_trapezoid_path,m_center[0],m_center[1],-view.angle);
var m_trapRS = pointsScale(m_trapR,m_center[0],m_center[1],view.scale);
var m_trapRST = pointsTranslate(m_trapRS,m_center2[0]-m_center[0],m_center2[1]-m_center[1]);
convertMercator2LLAndDraw(m_trapRST,'#f0f',4);
});
}
function waitForMapMoveCompletion(func) {
if(map.isMoving())
setTimeout(function() { waitForMapMoveCompletion(func); },250);
else
func();
}
function thenSetPitch(path,pitch) {
map.flyTo({ pitch:pitch } );
waitForMapMoveCompletion(function() { thenCalculateOptimalView(path); })
}
function displayFittedView(path,pitch) {
var bbox = getBoundingBox(path);
var path_cx = (bbox[0][0]+bbox[1][0])/2;
var path_cy = (bbox[0][1]+bbox[1][1])/2;
// start with a 'north up' view
map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [path_cx, path_cy],
zoom: 12
});
// use the bounding box to get into the right zoom range
map.on('load', function () {
addLayerToMap("path",path,'#888',8);
map.fitBounds(bbox);
waitForMapMoveCompletion(function() { thenSetPitch(path,pitch); });
});
}
window.onload = function(e) {
displayFittedView(myPath,60);
}
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.css' rel='stylesheet' />
<div id='map'></div>

Smallest surrounding rectangle would be specific to pitch=0 (looking directly down).
One option is to continue with smallest surrounding rectangle approach and calculate the transformation of the target area - just like a 3d engine does. If this is what you do maybe skim through unity docs to better understand the mechanics of viewing frustum
I feel this wouldn't be appropriate for your problem though as you'd have to re-calculate a 2d rendering of the target area from different angles, a relatively expensive brute force.
Another way to normalize the calculation would be to render a viewport projection into target area plane. See for yourself:
Then all you have to do is "just" figure out the largest size your original convex hull can fit into a trapezoid of that shape (specifically a convex isosceles trapezoid since we don't manipulate camera roll).
This is where I get a little out of depth and don't know where to point you for a calculation. I figure it's at least cheaper to iterate over possible solutions in this 2D space though.
P.S: One more thing to keep in mind is the viewport projection shape will be different depending on FOV (field of view).
This changes when you resize the browser viewport, but the property doesn't seem to be exposed in mapbox-gl-js.
Edit:
After some thought I feel the best mathematical solution can feel a little "dry" in reality. Not being across the use case and, possibly, making some wrong assumptions, I'd ask these questions:
For a route that's roughly a straight line, would it always be panned in so the ends are at bottom left and top right corners? That would be close to "optimal" but could get... boring.
Would you want to keep more of the path closer to the viewport? You can lose route detail if a large portion of it is far away from the viewport.
Would you pick points of interest to focus on? Those could be closer to the viewport.
Perhaps it would be handy to classify different types of routes by shape of hull and create panning presets?

Hopefully this can point you in the right direction with some tweaking.
First I set up the two points we want to show
let pointA = [-70, 43]
let pointB = [-83, 32]
Then I found the middle of those two points. I made my own function for this, but it looks like turf can do this.
function middleCoord(a, b){
let x = (a - b)/2
return _.min([a, b]) + x
}
let center = [middleCoord(pointA[0], pointB[0]), middleCoord(pointA[1], pointB[1])]
I used turfs bearing function to have the view from the 2nd point look at the first point
let p1 = turf.point(pointA)
let p2 = turf.point(pointB)
let points = turf.featureCollection([p1, p2])
let bearing = turf.bearing(p2, p1)
Then I call the map and run the fitBounds function:
var map = new mapboxgl.Map({
container: 'map', // container id
style: 'mapbox://styles/mapbox/outdoors-v10', //hosted style id
center: center, // starting position
zoom: 4, // starting zoom
pitch: 60,
bearing: bearing
})
map.fitBounds([pointA, pointB], {padding: 0, offset: 0})
Here's a codepen: https://codepen.io/thejoshderocher/pen/BRYGXq
To adjust the bearing to best use the screen size is to get the size of the window and adjust the bearing to take the most advantage of the available screen space. If it's a mobile screen in portrait, this bearing work perfect. If you are on a desktop with a wide view you will need to rotate so point A is in one of the top corners.

Generate random geo coordinates within specific radius from seed point

I'm using the following function to generate random geo coordinates within a specified radius from a seed point:
function randomGeo(center, radius) {
var y0 = center.latitude;
var x0 = center.longitude;
var rd = radius / 111300;
var u = Math.random();
var v = Math.random();
var w = rd * Math.sqrt(u);
var t = 2 * Math.PI * v;
var x = w * Math.cos(t);
var y = w * Math.sin(t);
var xp = x / Math.cos(y0);
return {
'latitude': y + y0,
'longitude': xp + x0
};
}
I do this in a loop, several times, using a 2000m radius and the following seed point:
location: { // Oxford
latitude: 51.73213,
longitude: -1.20631
}
I'd expect all of these results to be within 2000m; instead, I'm seeing values upwards of 10000m:
[ { latitude: 51.73256540025445, longitude: -1.3358092771716716 }, // 3838.75070783092
{ latitude: 51.7214165686511, longitude: -1.1644147572878725 }, // 3652.1890457730474
{ latitude: 51.71721400063117, longitude: -1.2082082568884593 }, // 8196.861603477768
{ latitude: 51.73583824510363, longitude: -1.0940424351649711 }, // 5104.820455873758
{ latitude: 51.74017571473442, longitude: -1.3150742602532257 }, // 4112.3279147866215
{ latitude: 51.73496163915278, longitude: -1.0379454413532996 }, // 9920.01459343298
{ latitude: 51.73582333121239, longitude: -1.0939302282840453 }, // 11652.160906253064
{ latitude: 51.72145745285658, longitude: -1.2491630482776055 }, // 7599.550622138115
{ latitude: 51.73036335927129, longitude: -1.3516902043395063 }, // 8348.276271205428
{ latitude: 51.748104753808924, longitude: -1.2669212014250266 }, // 8880.760669882042
{ latitude: 51.72010719621805, longitude: -1.327161328951446 }, // 8182.466715589904
{ latitude: 51.725727610071125, longitude: -1.0691503599266818 } ] // 2026.3687763449955
Given that I (shamelessly!) plagiarized this solution from elsewhere (albeit I've seen several similar implementations), I can't seem to figure out where the math is going wrong.
(Also, in case you want it, this is how I'm calculating the distance. Pretty sure this is correct.)
function distance(lat1, lon1, lat2, lon2) {
var R = 6371000;
var a = 0.5 - Math.cos((lat2 - lat1) * Math.PI / 180) / 2 + Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) * (1 - Math.cos((lon2 - lon1) * Math.PI / 180)) / 2;
return R * 2 * Math.asin(Math.sqrt(a));
}

The problem seems to stem from the fact that this is just an inaccurate calculation depending on which center point you are using. Particularly this line:
var xp = x / Math.cos(y0);
Removing this line and changing longitude to
'longitude': x + x0
Seems to keep all of the points within the specified radius, although without this line it seems the points will not completely fill out east to west in some cases.
Anyway, I found someone experiencing a similar issue here with someone elses Matlab code as a possible solution. Depends on how uniformly spread out you need the random points if you wanted to work with a different formula.
Here is a google maps visualization of what's going on with your provided formula:
<!doctype html>
<html>
<head>
<script type="text/javascript" src="//maps.google.com/maps/api/js?sensor=false"></script>
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script>
var distanceLimit = 2000; //in meters
var numberRandomPoints = 200;
var mapZoomLevel = 11;
var locationindex = 0;
var locations = [
{'name': 'Oxford, England', 'latitude': 51.73213, 'longitude': -1.20631},
{'name': 'Quito, Ecuador', 'latitude': -0.2333, 'longitude': -78.5167},
{'name': 'Ushuaia, Argentina', 'latitude': -54.8000, 'longitude': -68.3000},
{'name': 'McMurdo Station, Antartica', 'latitude': -77.847281, 'longitude': 166.667942},
{'name': 'Norilsk, Siberia', 'latitude': 69.3333, 'longitude': 88.2167},
{'name': 'Greenwich, England', 'latitude': 51.4800, 'longitude': 0.0000},
{'name': 'Suva, Fiji', 'latitude': -18.1416, 'longitude': 178.4419},
{'name': 'Tokyo, Japan', 'latitude': 35.6833, 'longitude': 139.6833},
{'name': 'Mumbai, India', 'latitude': 18.9750, 'longitude': 72.8258},
{'name': 'New York, USA', 'latitude': 40.7127, 'longitude': -74.0059},
{'name': 'Moscow, Russia', 'latitude': 55.7500, 'longitude': 37.6167},
{'name': 'Cape Town, South Africa', 'latitude': -33.9253, 'longitude': 18.4239},
{'name': 'Cairo, Egypt', 'latitude': 30.0500, 'longitude': 31.2333},
{'name': 'Sydney, Australia', 'latitude': -33.8650, 'longitude': 151.2094},
];
</script>
</head>
<body>
<div id="topbar">
<select id="location_switch">
<script>
for (i=0; i<locations.length; i++) {
document.write('<option value="' + i + '">' + locations[i].name + '</option>');
}
</script>
</select>
<img src="http://google.com/mapfiles/ms/micons/ylw-pushpin.png" style="height:15px;"> = Center
<img src="https://maps.gstatic.com/mapfiles/ms2/micons/red.png" style="height:15px;"> = No Longitude Adjustment
<img src="https://maps.gstatic.com/mapfiles/ms2/micons/pink.png" style="height:15px;"> = With Longitude Adjustment (var xp = x / Math.cos(y0);)
</div>
<div id="map_canvas" style="position:absolute; top:30px; left:0px; height:100%; height:calc(100% - 30px); width:100%;overflow:hidden;"></div>
<script>
var markers = [];
var currentcircle;
//Create the default map
var mapcenter = new google.maps.LatLng(locations[locationindex].latitude, locations[locationindex].longitude);
var myOptions = {
zoom: mapZoomLevel,
scaleControl: true,
center: mapcenter
};
var map = new google.maps.Map(document.getElementById('map_canvas'), myOptions);
//Draw default items
var centermarker = addCenterMarker(mapcenter, locations[locationindex].name + '<br>' + locations[locationindex].latitude + ', ' + locations[locationindex].longitude);
var mappoints = generateMapPoints(locations[locationindex], distanceLimit, numberRandomPoints);
drawRadiusCircle(map, centermarker, distanceLimit);
createRandomMapMarkers(map, mappoints);
//Create random lat/long coordinates in a specified radius around a center point
function randomGeo(center, radius) {
var y0 = center.latitude;
var x0 = center.longitude;
var rd = radius / 111300; //about 111300 meters in one degree
var u = Math.random();
var v = Math.random();
var w = rd * Math.sqrt(u);
var t = 2 * Math.PI * v;
var x = w * Math.cos(t);
var y = w * Math.sin(t);
//Adjust the x-coordinate for the shrinking of the east-west distances
var xp = x / Math.cos(y0);
var newlat = y + y0;
var newlon = x + x0;
var newlon2 = xp + x0;
return {
'latitude': newlat.toFixed(5),
'longitude': newlon.toFixed(5),
'longitude2': newlon2.toFixed(5),
'distance': distance(center.latitude, center.longitude, newlat, newlon).toFixed(2),
'distance2': distance(center.latitude, center.longitude, newlat, newlon2).toFixed(2),
};
}
//Calc the distance between 2 coordinates as the crow flies
function distance(lat1, lon1, lat2, lon2) {
var R = 6371000;
var a = 0.5 - Math.cos((lat2 - lat1) * Math.PI / 180) / 2 + Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) * (1 - Math.cos((lon2 - lon1) * Math.PI / 180)) / 2;
return R * 2 * Math.asin(Math.sqrt(a));
}
//Generate a number of mappoints
function generateMapPoints(centerpoint, distance, amount) {
var mappoints = [];
for (var i=0; i<amount; i++) {
mappoints.push(randomGeo(centerpoint, distance));
}
return mappoints;
}
//Add a unique center marker
function addCenterMarker(centerposition, title) {
var infowindow = new google.maps.InfoWindow({
content: title
});
var newmarker = new google.maps.Marker({
icon: 'http://google.com/mapfiles/ms/micons/ylw-pushpin.png',
position: mapcenter,
map: map,
title: title,
zIndex: 3
});
google.maps.event.addListenerOnce(map, 'tilesloaded', function() {
infowindow.open(map,newmarker);
});
markers.push(newmarker);
return newmarker;
}
//Draw a circle on the map
function drawRadiusCircle (map, marker, distance) {
currentcircle = new google.maps.Circle({
map: map,
radius: distance
});
currentcircle.bindTo('center', marker, 'position');
}
//Create markers for the randomly generated points
function createRandomMapMarkers(map, mappoints) {
for (var i = 0; i < mappoints.length; i++) {
//Map points without the east/west adjustment
var newmappoint = new google.maps.LatLng(mappoints[i].latitude, mappoints[i].longitude);
var marker = new google.maps.Marker({
position:newmappoint,
map: map,
title: mappoints[i].latitude + ', ' + mappoints[i].longitude + ' | ' + mappoints[i].distance + 'm',
zIndex: 2
});
markers.push(marker);
//Map points with the east/west adjustment
var newmappoint = new google.maps.LatLng(mappoints[i].latitude, mappoints[i].longitude2);
var marker = new google.maps.Marker({
icon: 'https://maps.gstatic.com/mapfiles/ms2/micons/pink.png',
position:newmappoint,
map: map,
title: mappoints[i].latitude + ', ' + mappoints[i].longitude2 + ' | ' + mappoints[i].distance2 + 'm',
zIndex: 1
});
markers.push(marker);
}
}
//Destroy all markers
function clearMarkers() {
for (var i = 0; i < markers.length; i++) {
markers[i].setMap(null);
}
markers = [];
}
$('#location_switch').change(function() {
var newlocation = $(this).val();
clearMarkers();
mapcenter = new google.maps.LatLng(locations[newlocation].latitude, locations[newlocation].longitude);
map.panTo(mapcenter);
centermarker = addCenterMarker(mapcenter, locations[newlocation].name + '<br>' + locations[newlocation].latitude + ', ' + locations[newlocation].longitude);
mappoints = generateMapPoints(locations[newlocation], distanceLimit, numberRandomPoints);
//Draw default items
currentcircle.setMap(null);
drawRadiusCircle(map, centermarker, distanceLimit);
createRandomMapMarkers(map, mappoints);
});
</script>
</body>
</html>

You can generate points with a random bearing and distance from the center by moving some distance using vincenty distances (see this stackoverflow answer). In Python, for example, you could use the geopy package.
import random
from geopy import Point
from geopy.distance import geodesic
def generate_point(center: Point, radius: int) -> Point:
radius_in_kilometers = radius * 1e-3
random_distance = random.random() * radius_in_kilometers
random_bearing = random.random() * 360
return geodesic(kilometers=random_distance).destination(center, random_bearing)
radius = 2000
center = Point(51.73213, -1.20631)
points = [generate_point(center, radius) for _ in range(3000)]
Distances are confirmed with:
assert all(geodesic(center, point).meters <= radius for point in points)

Here a simple Vanilla Javascript solution that works like a charm. I want to give credits where it's due and where I found it : https://gist.github.com/fajarlabs/af9e0859fc29b2107bd1797536d2ff2d
/**
* Generates number of random geolocation points given a center and a radius.
* #param {Object} center A JS object with lat and lng attributes.
* #param {number} radius Radius in meters.
* #param {number} count Number of points to generate.
* #return {array} Array of Objects with lat and lng attributes.
*/
function generateRandomPoints(center, radius, count) {
var points = [];
for (var i=0; i<count; i++) {
points.push(generateRandomPoint(center, radius));
}
return points;
}
/**
* Generates number of random geolocation points given a center and a radius.
*
* #param {Object} center A JS object with lat and lng attributes.
* #param {number} radius Radius in meters.
* #return {Object} The generated random points as JS object with lat and lng attributes.
*/
function generateRandomPoint(center, radius) {
var x0 = center.lng;
var y0 = center.lat;
// Convert Radius from meters to degrees.
var rd = radius/111300;
var u = Math.random();
var v = Math.random();
var w = rd * Math.sqrt(u);
var t = 2 * Math.PI * v;
var x = w * Math.cos(t);
var y = w * Math.sin(t);
var xp = x/Math.cos(y0);
// Resulting point.
return {'lat': y+y0, 'lng': xp+x0};
}
// Usage Example.
// Generates 100 points that is in a 1km radius from the given lat and lng point.
var randomGeoPoints = generateRandomPoints({'lat':24.23, 'lng':23.12}, 1000, 100);
console.log(randomGeoPoints);

Polygon Draw around center points

I have tried lots but could not figure out the problem. I want to draw a polygon around specific lat,lng. The polygon will consists of 13 coordinates in specific radius.
Person inter the address and radius in text box.
Geo code get lat,lng of that address
Center the map to there.
Draw the polygon around that center point with radius
The polygon should consists of 13 coordinates
Code
function showAddress(address, miles) {
var geocoder = new google.maps.Geocoder();
geocoder.geocode({
address : address
}, function(results, status) {
if(status == google.maps.GeocoderStatus.OK) {
//searchLocationsNear(results[0].geometry.location);
var cordinate = results[0].geometry.location;
//alert(cordinate);
var mapOptions = {
center : cordinate,
zoom : 8,
mapTypeId : google.maps.MapTypeId.ROADMAP,
overviewMapControl : true,
overviewMapControlOptions : {
opened : true,
position : google.maps.ControlPosition.BOTTOM_LEFT
}
};
//
//var address = document.getElementById("address").value;
var radius = 1;
var latitude = 23.1793013;
var longitude = 75.78490970000007;
//Degrees to radians
var d2r = Math.PI / 180;
// Radians to degrees
var r2d = 180 / Math.PI;
// Earth radius is 3,963 miles
var cLat = (radius / 3963) * r2d;
var cLng = cLat / Math.cos(latitude * d2r);
//Store points in array
var points = [];
alert("declare array");
var bounds = new google.maps.LatLngBounds();
// Calculate the points
// Work around 360 points on circle
for(var i = 0; i < 13; i++) {
var theta = Math.PI * (i / 180);
// Calculate next X point
circleY = longitude + (cLng * Math.cos(theta));
//console.log("CircleY:"+circleY);
// Calculate next Y point
circleX = latitude + (cLat * Math.sin(theta));
//console.log("circleX:"+circleX);
// Add point to array
var aPoint = new google.maps.LatLng(circleX, circleY);
points.push(aPoint);
bounds.extend(aPoint);
}
points.push(points[0]);
//console.log(points);
//to complete circle
var colors = ["#CD0000", "#2E6444", "#003F87"];
var Polyline_Path = new google.maps.Polyline({
path : points,
strokeColor : colors[0],
// color of the outline of the polygon
strokeOpacity : 1,
// between 0.0 and 1.0
strokeWeight : 1,
// The stroke width in pixels
fillColor : colors[1],
fillOpacity : 0
});
var map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions);
Polyline_Path.setMap(map);
} else {
alert(address + ' not found');
}
});
}

Replace i<13;i++ by
i<360;i+=360/13
this will work
thank
edit: the last point isn't needed since gmap will close it automagically

I believe that cLng should be changed to:
var cLng = cLat * Math.cos(latitude * d2r);
(to get a perfect circle, that is)

Develop Reference

JavaScript is the programming language of the Web.