Period-3 Geo-data, GeoJSON, Geospatial Queries with MongoDB, React Native/Expo’s Location and MapView Components
https://github.com/grem848/mini-project-fullstackjs2019/blob/master/makeData.js
// add positions to 3 test users above
var kurt = await userFacade.findByUsername("ckw");
var jane = await userFacade.findByUsername("cjw");
var bo = await userFacade.findByUsername("cbw");
console.log("Add positions to jane, bo and a")
var positions = [
positionCreator(12.51293635, 55.77066395, jane._id, true),
positionCreator(12.53932071, 55.76679288, bo._id, true),
positionCreator(12.544750, 55.775508, kurt._id, true)
]
console.log(`${kurt.firstName}'s ID: ${kurt._id}`);
console.log(`${jane.firstName}'s ID: ${jane._id}`);
console.log(`${bo.firstName}'s ID: ${bo._id}`);
await Position.insertMany(positions);https://github.com/grem848/mini-project-fullstackjs2019/blob/master/makeData.js
console.log("Create Area")
const polygon = {
type: "Polygon",
name: "TestArea",
coordinates: [
[
[12.541322708129883, 55.77415929267225],
[12.577714920043945, 55.7767661102896],
[12.576856613159178, 55.78038640106636],
[12.58277893066406, 55.78231708529588],
[12.581834793090819, 55.78661251449472],
[12.578573226928711, 55.788784180465655],
[12.576513290405273, 55.79433344350657],
[12.569818496704102, 55.795732698062174],
[12.541322708129883, 55.77415929267225]
]
]
};
const area = await new Area(polygon).save();
console.log("Saved an area: ", area);https://github.com/grem848/mini-project-fullstackjs2019/blob/master/facades/queryFacade.js
// get distance to friend
const User = require('../models/User');
const Position = require('../models/Position');
const Area = require('../models/Area');
const gju = require('geojson-utils');
async function getDistanceToUser(lon, lat, username) {
const user_id = await User.findOne({ userName: username }).select({ _id: 1 });
if (user_id !== null) {
return (userPos = await Position.findOne({ user: user_id })
.catch(() => {
throw new Error(`${username} doesn't have a Location`);
})
.then(async (data) => {
if (data === null) {
throw new Error(`${username} doesn't have a Location`);
} else {
const point = { type: 'Point', coordinates: [ lon, lat ] };
const distance = await gju.pointDistance(point, data.loc); // finds distance in meters between Point and User
return { username: username, distance };
}
}));
} else {
throw new Error(`User: ${username} doesn't Exist`);
}
}
async function findNearbyPlayers(lon, lat, dist) {
return Position.find({
loc: {
$near: {
$geometry: { type: 'Point', coordinates: [ lon, lat ] },
$minDistance: 0.1,
$maxDistance: dist
}
}
})
.populate('user', 'userName firstName') // you can add more variables if you like
.select({ created: 0, __v: 0, _id: 0, 'loc.type': 0, 'user._id': 0 });
}
async function isUserinArea(areaName, username) {
const area = await Area.findOne({ name: areaName });
if (area === null) {
throw new Error('Area Not Found');
}
const user_id = await User.findOne({ userName: username }).select({ _id: 1 });
if (user_id !== null) {
const userPos = await Position.findOne({
user: user_id,
loc: {
$geoWithin: {
$geometry: area
}
}
}).catch(() => {
throw new Error(`${username} doesn't have a Location`);
});
var status = false;
var msg = 'Point was NOT inside tested polygon';
if (userPos !== null) {
status = true;
msg = 'Point was inside the tested polygon';
}
return { status, msg };
} else {
throw new Error(`User: ${username} doesn't Exist`);
}
}
module.exports = {
getDistanceToUser,
findNearbyPlayers,
isUserinArea
};https://github.com/grem848/mini-project-fullstackjs2019/blob/master/makeData.js
https://github.com/grem848/mini-project-fullstackjs2019/tree/master/test
There is no order for longitude,latitude
HOWEVER! In mathematical functions x,y are used, for the geographic coordinate system we use lon,lat or inverse. The x-axis relates to longitude and y to latitude and the x,y order is ususally prefered.
From (old) navigation and geography latitude and longitude was used. To figure out your latitude, you just needed (a) the calendar date, and (b) some astronomical measurements (like for instance, the angle of the sun above the horizon at its highest point on a given day as measured from your ship).
To figure out your longitude, you would need a precise clock tracking time from some reference point.
This has made the standard for many services to latitude, longitude.
/* GET distance to user from username and coordinates */
router.get('/distanceToUser/:lon/:lat/:username', async function(req, res, next) {
var { lon, lat, username } = req.params;
var obj = await queryFacade.getDistanceToUser(lon, lat, username).catch((err) => {
res.status(404).json({ msg: err.message });
});
if (obj !== undefined) {
res.status(200).json({ distance: obj.distance, to: obj.username });
}
});const gju = require('geojson-utils');
async function getDistanceToUser(lon, lat, username) {
const user_id = await User.findOne({ userName: username }).select({ _id: 1 });
if (user_id !== null) {
return (userPos = await Position.findOne({ user: user_id })
.catch(() => {
throw new Error(`${username} doesn't have a Location`);
})
.then(async (data) => {
if (data === null) {
throw new Error(`${username} doesn't have a Location`);
} else {
const point = { type: 'Point', coordinates: [ lon, lat ] };
const distance = await gju.pointDistance(point, data.loc); // finds distance in meters between Point and User
return { username: username, distance };
}
}));
} else {
throw new Error(`User: ${username} doesn't Exist`);
}
}MongoDB provides the following geospatial query operators:
Name Description
-
$geoIntersects
- Selects geometries that intersect with a GeoJSON geometry. The 2dsphere index supports $geoIntersects.
-
$geoWithin
- Selects geometries within a bounding GeoJSON geometry. The 2dsphere and 2d indexes support $geoWithin.
-
$near
- Returns geospatial objects in proximity to a point. Requires a geospatial index. The 2dsphere and 2d indexes support $near.
-
$nearSphere
- Returns geospatial objects in proximity to a point on a sphere. Requires a geospatial index. The 2dsphere and 2d indexes support $nearSphere.
Indexes support the efficient resolution of queries. Without indexes, MongoDB must scan every document of a collection to select those documents that match the query statement. This scan is highly inefficient and require MongoDB to process a large volume of data.
Here key is the name of the field on which you want to create index and 1 is for ascending order. To create index in descending order you need to use -1.
async function isUserinArea(areaName, username) {
const area = await Area.findOne({ name: areaName });
if (area === null) {
throw new Error('Area Not Found');
}
const user_id = await User.findOne({ userName: username }).select({ _id: 1 });
if (user_id !== null) {
const userPos = await Position.findOne({
user: user_id,
loc: {
$geoWithin: {
$geometry: area
}
}
}).catch(() => {
throw new Error(`${username} doesn't have a Location`);
});
var status = false;
var msg = 'Point was NOT inside tested polygon';
if (userPos !== null) {
status = true;
msg = 'Point was inside the tested polygon';
}
return { status, msg };
} else {
throw new Error(`User: ${username} doesn't Exist`);
}
}https://github.com/pernillelorup/mini-project-native-app https://expo.io/@grem848/mini-project-app-2019