Is it possible to get places by latitude/longitude and radius using the Graph API (or by address/zip)? I don't see it anywhere in the documentation
The following format for the search URL will return a list of places near a location:
https://graph.facebook.com/search?type=place¢er=<lat>,<lon>&distance=1000&access_token=<token>
I'm not sure on the units of the "distance" parameter.
I don't know much about the facebook API, but if you can pull the lat/long of two places, you can calculate their distance quite easily. Here it is in JavaScript, but it's portable to about any language:
var R = 6371; // km .. use 3963 for miles
var dLat = (lat2-lat1).toRad();
var dLon = (lon2-lon1).toRad();
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c; // km
Hopefully this helps you with your endeavor.
Related
I have multiple locations and current location, i want to find distance between my current location and other given location of google map flutter.
please provide any method or library which can easily calculate time and distance.I am Using this code but i can not find correct distance.
double _coordinateDistance(lat1, lon1, lat2, lon2) {
var p = 0.017453292519943295;
var c = cos;
var a = 0.5 - c((lat2 - lat1) * p) / 2 +
c(lat1 * p) * c(lat2 * p) * (1 - c((lon2 - lon1) * p)) / 2;
return 12742 * asin(sqrt(a));}
use https://pub.dev/packages/flutter_locations_distance package
add your multiple locations into lat and lon array and use this code
for(int i=0;i<locCount;i++){
double distance;
// Platform messages may fail, so we use a try/catch PlatformException.
try {
distance = await FlutterLocationsDistance().distanceBetween(currentLat,
currentLon, lat[i], lon[i]);
} on PlatformException {
distance = -1.0;
}
}
and for each multiple locations you can get the distance between current location and other locations.
to get your current location use https://pub.dev/packages/location package.
for the time you can use https://pub.dev/packages/stop_watch_timer package
I have two locations and I have the formula to get the distance between them but I want to calculate the travel time between them without using google maps or any API calling. Is there any formula to do that in flutter?
I think the real travel time depends on a lot of factors, for example the road you take or the speed limit.
Whitout some complex elaboration, which are usually perfomed by a backend, I don't think it is possible to calculate it.
Anyway, since you have got the distance, you could simply estimate it by giving a supposed speed and then using basic physics formulas.
time = distance / speed.
You cannot find the travel distance between two locations without using the Google API.
However you can get the air distance in meters using this formula in flutter.
double calculateDistance(
double lat1, double lon1, double lat2, double lon2) {
var p = 0.017453292519943295;
var c = cos;
var a = 0.5 -
c((lat2 - lat1) * p) / 2 +
c(lat1 * p) * c(lat2 * p) * (1 - c((lon2 - lon1) * p)) / 2;
var temp = 12742 * asin(sqrt(a));
return (temp * 1000);
}
How to calculate distance between two location in dart?
Without using plugin
double calculateDistance(lat1, lon1, lat2, lon2){
var p = 0.017453292519943295;
var c = cos;
var a = 0.5 - c((lat2 - lat1) * p)/2 +
c(lat1 * p) * c(lat2 * p) *
(1 - c((lon2 - lon1) * p))/2;
return 12742 * asin(sqrt(a));
}
result is KM. if you want meter just multiply by 1000. return 1000 * 12742 * asin(sqrt(a))
You can use geolocator plugin to calculate to distances between two coordinates:
An Example:
var _distanceInMeters = await Geolocator().distanceBetween(
_latitudeForCalculation,
_longitudeForCalculation,
_currentPosition.latitude,
_currentPosition.longitude,
);
Check out GeoLocator Plugin for more info.
Check out latlong. It's a package dedicated to work with coordinates and features sophisticated calculations.
Unlike packages like geolocator it does not come with integrated location services and can be used alongside packages specialized for that.
You can use latlong2 which is the continuation of latlong. It has features like distance calculation and path drawing. So you can get distance as path distance as well as direct distance.
I am using postgres and postgis.
I have Posts which have a geometry, with an attribute visible_within_m which is how many meters from that point the Post should be shown in results.
I can find Posts within some random radius of some random points by doing ST_DWithin(geometry, ST_SetSRID(ST_Point(a, b), 4326), 10000)
However, I want to know how many Posts are visible with a radius of some random point.
How can I look up how many Posts are visible within a radius of some arbitrary point?
Is there a better way to do this?
You can calculate the distance between each point and the center of your circle. If the distance is grater than the radius then it is outside otherwise it's inside.
const EARTH_RADIUS = 6371000;
const toRad = function(num){return num*Math.PI/180};
var calculateDistance =
function(lat1, lon1, lat2, lon2){
var dLat = toRad(lat2 - lat1);
var dLon = toRad(lon2 - lon1);
var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(toRad(lat1)) *
Math.cos(toRad(lat2)) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
var distance = EARTH_RADIUS * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
return distance;
}
Instead of using a constant value for the distance, use the value stored in visible_within_m
SELECT * FROM mytable
WHERE ST_DWithin(geometry, ST_SetSRID(ST_Point(a, b), 4326), visible_within_m);
On a side note, st_dwithin with geometries uses the distance unit of the projection, so for 4326 it is a (meaningless) distance in degrees, not in meters.
I am using Node.js and MongoDB.
Let say I have predefined few cities (e.g. Seattle, Miami, New York) with Lat & Lon. and there is a user click to my website and I know his IP address, and find out the lat & lon. Then I want to know which city that I've defined is the closest to the user.
I know I can do it using Mongo's geospatial feature. but it would be quite 'expensive' to use DB to calculate that for every web request.
Is there a Node.js NPM package that can do the geo feature as I described above?
How many "pre-defined" cities are you working with? If it's a small number, you could probably just store the list in memory and do a linear scan.
Also, you should probably just give the mongo geospatial query a try to get an idea of exactly how expensive it is, before assuming that it's unreasonable - if you index the city locations and the, it will be pretty fast..
If you are dealing with a lot of points, still don't want to rely on mongo geo-indexing, and need something really specialized, maybe an R-Tree would be worth experimenting with. Here's an r-tree implementation for javascript. https://github.com/imbcmdth/RTree
If you already have the user's location and the location of each city, it should be quite fast to compute the distance to the nearest. Check out this site: http://www.movable-type.co.uk/scripts/latlong.html
I have used the first algorithm a few times.
function getDistance(lat1,lat2,lon1,lon2){
var R = 6371; // km
var c = Math.PI / 180;
var dLat = (lat2-lat1) * c;
var dLon = (lon2-lon1) * c;
var lat1 = lat1 * c;
var lat2 = lat2 * c;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.sin(dLon/2) * Math.sin(dLon/2) * Math.cos(lat1) * Math.cos(lat2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
return d;
}
var closest, dist = Number.MAX_VALUE;
for(var i = 0, l=cities.length;i<l;++i){
if(getDistance(cities[i].longitude, cities[i].latitude, user.longitude, user.latitude) < max){
closest = cities[i];
}
}
alert(closest.name + ' is the winner :)');
You might want to add some exception handling here :)