Develop Reference

Geo Coordinates (Long,Lat) to Meters (x,y)

I am working coordinates system as shown below:
x and y are in meters. I am interested in only positive x,y. I want to convert (x,y) to (lat,lon) and vise versa.
I thought it is simple and I dont see a problem with my solutions below. But I am not getting very correct results.
My Solution:
As we see in the image below, I considered the Latitude and Longitude as angles of 2 circles:
1. (x,y) to (lat,lon)
I applied the Arc Length formula (here), shown below, on both; x and y
Hence, my functions are:
private static double calculateLat(float x) {
int earthRadius = 6371000;
return REF_LOC.getLatitude() + x*360/(2*PI*earthRadius);
}
private static double calculateLong(float y) {
int earthRadius = 6371000;
return REF_LOC.getLongitude() + y*360/(2*PI*earthRadius);
}
REF_LOC is the reference Geo Location for which (x,y) are (0,0). It can be any point on earth.
2. (lat,lon) to (x,y)
For this I am simply using this:
int calculateX(double longitude){
Location.distanceBetween(REF_LOC.getLatitude(), REF_LOC.getLongitude(),
REF_LOC.getLatitude(), lonDeg, results);
return results[0];
}
int calculateY(double latitude){
Location.distanceBetween(REF_LOC.getLatitude(), REF_LOC.getLongitude(),
latDeg, REF_LOC.getLongitude(), results);
return results[0];
}
But I am getting inconsistent results. First I use solution 1 and convert some value (x,y) to (lat,long). But when I use the same (lat,long) back to (x,y) using solution 2, I get about 2 meters difference in x and 10 meters in y. Can anyone help me identify the problem please?

Alluding to my comment on spherical vs elliptical calculations, another way to look at difference in distance calculations for spherical vs elliptical distance is to use the 2 available utilities:
// For REF_LOC = (70, 20)
// Compute a lat/lng due east of a REF_LOC and compute distance using both
// available methods.
LatLng P = SphericalUtil.computeOffsetOrigin(REF_LOC, 20000, 90.0);
// And then compute a distance
d = SphericalUtil.computeDistanceBetween(REF_LOC, P);
Location.distanceBetween(REF_LOC.latitude, REF_LOC.longitude, P.latitude, P.longitude, results);
// d = 20000.000000000036
// results[0] = 20081.818
// and for a REF_LOC = (0, 20)
// d = 20000.000000000127
// results[0] = 20022.377
What's also interesting is the SphericalUtil.computeOffsetOrigin() produces error
in latitude increasing from equator to pole making it non-symmetrical. Yet the resulting distances are essentially exact.
I'd recommend using SphericalUtil.computeOffsetOrigin to compute the X/Y breaking
it into the latitude and longitude offsets as you are doing.
Finally demonstrating the SphericalUtil solution:
// Start with some arbitrary x/y relative to REF_LOC
double Rx = 125.0;
double Ry = 73.0;
// Compute a lat/lon from REF_LOC to the point
LatLng Rll = new LatLng(SphericalUtil.computeOffsetOrigin(REF_LOC, Ry, 180).latitude,
SphericalUtil.computeOffsetOrigin(REF_LOC, Rx, 270).longitude);
// And recompute the x/y components of the lat/lon
double Rxx = SphericalUtil.computeDistanceBetween(REF_LOC, new LatLng(REF_LOC.latitude, Rll.longitude));
double Ryy = SphericalUtil.computeDistanceBetween(REF_LOC, new LatLng(Rll.latitude, REF_LOC.longitude));
Resulting in:
Rx/Ry = (125.0, 73.0)
Rxx/Ryy = (125.00000004545973, 73.00000000137051)
Acceptable error I assume.
So the parting question is - what does the x/y really represent?
Reference the source for both utilities for more information:
Location
SphericalUtil

How can i check if location is in my radius?

i trying to get if location is in my radius.
i.e I have my current location "LatLng" object and i have one more "LatLng" object and i want to check if the two object are in rang of 1km?
How can i implement that?

In Location.distanceBetween() function provide you distance in meters and float value ..
distanceBetween(double startLatitude, double startLongitude, double
endLatitude, double endLongitude, float[] results) Computes the
approximate distance in meters between two locations, and optionally
the initial and final bearings of the shortest path between them.
use this it working i've already checked it .....
float[] dist = new float[1];
Location.distanceBetween(firstLoaction.latitude,firstLoaction.longitude,anotherLocation.latitude,anotherLocation.longitude,dist);
if(dist[0]/1000 > 1){
//here your code or alert box for outside 1Km radius area
}
NOTE:- For getting the location distance always use Location.distanceBetween() which is provide by ANDROID .

double distanceInKiloMeters = (currentLocation.distanceTo(someLocation)) / 1000; // as distance is in meter
if(distanceInKiloMeters <= 1) {
// It is in range of 1 km
}
else {
// not in range of 1 km
}

you can try converting LatLng to Location object for both first and then using distanceTo method to find the distance between those two and check if it is 1km or not

distanceto methode to get distance from locCenter and point and just substitute this distance from the radius if <0 so the point out of range , else the point in border or inside the range.. good luck

distanceto functon Returning wrong format Android

I am calculating distance between two location using latitude and longitude... i am getting the distance easily and converting it into miles... but first difference value come in wrong format and other value coming right.
First distance is coming like this = 2.0E-4
While other like this = 48.8881
i have used the following code
Location l1 = new Location("One");
l1.setLatitude(cur_latitude);
l1.setLongitude(cur_longitude);
for (int i = 0; i < lctn.size(); i++) {
Location l2 = new Location("LocationB");
l2.setLatitude(lctn.get(i).getLocation_lat());
l2.setLongitude(lctn.get(i).getLocation_lng());
float distance = l1.distanceTo(l2);
distance =Float.parseFloat(new DecimalFormat("##.####").format( distance / 1000.0f));
Double mile = Double.parseDouble(new DecimalFormat("##.####").format(distance * 0.6214));
Log.e("km_", "" + distance);
Log.e("miles_", "" + mile);
Also please check whether i am using right formula for calculating miles....Thanks in Advance

Distance is in points that why it happening, You need to use accuracy variable and assign some value to this variable,
in my case i use
int accuracy = 20;
Then compare this accuracy with Location accuracy
if(l2.getAccuracy() <= accuracy ) {
Log.e("km_", "" + distance);
Log.e("miles_", "" + mile);
}
I suggest you to use fused location api for accurate distance.

Measure the distance between two locations by road

How can I measure distance between two location by road in my Android application? I wrote code that measure the distance in a straight line, but I need code for shortest distance by road. What should I change in my code for it?
public double updateDistance(Location location) {
float results[] = new float[3];
Location.distanceBetween(location.getLatitude(),
location.getLongitude(), mLatitude, mLongitude, results);
distance = results[0];
return distance;
}

Use the google maps api instead
https://developers.google.com/maps/documentation/distance-matrix/intro?hl=en
you can see this too
Google Map API v2 - Get Driving Distance from Current Location to Known Locations

Moving GPS coordinate

I am fairly new to Android programming, but I am getting pretty good at it (I think: ))
What I am doing is building a situated stories app. It is an app that places audio files at certain GPS markers and enables the user to listen to them at specific locations.
The next step is moving audio files. What I want to do is set a marker at a specific position in a city. (done). Next I want to check the location of a second marker that moves in a circle around it.
What I have so far is this:
public void checkCircularPosition(){
/*
* could be a solution?
*
radius = 250; //offset in meters
gpsLatCenter = 5.1164; //?how can i make this accurate in meters?
gpsLonCenter = 52.0963; //??how can i make this accurate in meters?
degree = 0; //should be variable over time (full circle in 1Hr, 3600sec --> 360/3600 = 0,1 deg/s)
radian;
radian = (degree/180)*Math.PI;
gpsCircleLat = gpsLatCenter+Math.cos(radian)*radius;
gpsCircleLon = gpsLonCenter-Math.sin(radian)*radius;
*/
}
Now, I have checked this code in adobe flash, which made a movie clip move around in a circle. So I know the calculations are somewhat right. But, I have no way of calculating the latitude and longitude of the resulting coordinates.
EDIT!!
i found the solution with the help posted below. still a lot of work to figure out how to use the results. anyway, i posted the resulting function below.
to make this work, you need _radius wich is 6371 (earth's radius), a bearing, a distance, and a start location.
thanks a lot guys!
public static void destinationPoint(double brng, double dist) {
dist = dist/_radius; // convert dist to angular distance in radians
brng = Math.toRadians(brng); //
double lat1 = Math.toRadians(_lat);
double lon1 = Math.toRadians(_lon);
double lat2 = Math.asin( Math.sin(lat1)*Math.cos(dist) + Math.cos(lat1)*Math.sin(dist)*Math.cos(brng) );
double lon2 = lon1 + Math.atan2(Math.sin(brng)*Math.sin(dist)*Math.cos(lat1), Math.cos(dist)-Math.sin(lat1)*Math.sin(lat2));
lon2 = (lon2+3*Math.PI) % (2*Math.PI) - Math.PI; // normalise to -180..+180º
Log.i(APPTAG, ""+Math.toDegrees(lat2));
Log.i(APPTAG, ""+Math.toDegrees(lon2));
Location movLoc = new Location("");
movLoc.setLatitude(Math.toDegrees(lat2));
movLoc.setLongitude(Math.toDegrees(lon2));
Log.i(APPTAG, ""+movLoc);
}

You should check the section Destination point given distance and bearing from start point at this website: http://www.movable-type.co.uk/scripts/latlong.html
That website has the proper formula for using your start point (gpsLatCenter/gpsLonCenter) and bearing (degree in you code) to compute the final lat/lon (gpsCircleLat/gpsCircleLon).