Calculating bounding box given center lat /long and distance on iOS? - ios

In my iOS app I have a lat and long that gives me my location. I want to be able to calculate the bounding box that satisfies a certain distance d from my location. How can I do this?
TRY 1:
So I tried the solution given by #Neeku. I can see how it's supposed to return the right information but unfortunately it's off. So I don't think I can use it.
The code I wrote is this and I pass in 1000 meters:
MKCoordinateRegion startRegion = MKCoordinateRegionMakeWithDistance(center, meters, meters);
CLLocationCoordinate2D northWestCorner, southEastCorner;
northWestCorner.latitude = startRegion.center.latitude + .5 * startRegion.span.latitudeDelta;
northWestCorner.longitude = startRegion.center.longitude - .5 * startRegion.span.longitudeDelta;
southEastCorner.latitude = startRegion.center.latitude - .5 * startRegion.span.latitudeDelta;
southEastCorner.longitude = startRegion.center.longitude - .5 * startRegion.span.longitudeDelta;
NSLog(#"CENTER <%#,%#>", #(center.latitude),#(center.longitude));
NSLog(#"NW <%#,%#>, SE <%#,%#>",#(northWestCorner.latitude),#(northWestCorner.longitude),#(southEastCorner.latitude),#(southEastCorner.longitude));
So then the result is:
CENTER <38.0826682,46.3028721>
NW <38.08717278501047,46.29717303828632>, SE <38.07816361498953,46.29717303828632>
I then put that in google maps and get this: (see screenshot)
So then to my understanding the 1000 meters should go from the center to the sides of the box. The map is measuring the corner which should be OVER 1000 meters and it's actually just over 800 meters. This is the problem I am trying to solve.
I tried this method before and the distances simply aren't accurate. So, this solution has not worked for me. If you have more suggestions or maybe want to point out what is done wrong here please let me know.
Thank you

Let's say that your desired distance is 111 meters. Then you use the following code:
// 111 kilometers / 1000 = 111 meters.
// 1 degree of latitude = ~111 kilometers.
// 1 / 1000 means an offset of coordinate by 111 meters.
float offset = 1.0 / 1000.0;
float latMax = location.latitude + offset;
float latMin = location.latitude - offset;
// With longitude, things are a bit more complex.
// 1 degree of longitude = 111km only at equator (gradually shrinks to zero at the poles)
// So need to take into account latitude too, using cos(lat).
float lngOffset = offset * cos(location.latitude * M_PI / 180.0);
float lngMax = location.longitude + lngOffset;
float lngMin = location.longitude - lngOffset;
latMax, latMin, lngMax, lngMin will give you your bounding box coordinates.
(You can change this code pretty easily if you need distance other than 111 meters. Just update offset variable accordingly).

You can add/subtract half of the span from the latitude and longitude respectively and you get the values that you need:
CLLocationCoordinate2D centerCoord = CLLocationCoordinate2DMake(38.0826682, 46.3028721);
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(centerCoord, 1000, 1000);
double latMin = region.center.latitude - .5 * startRegion.span.latitudeDelta;
double latMax = region.center.latitude + .5 * startRegion.span.latitudeDelta;
double lonMin = region.center.longitude - .5 * startRegion.span.longitudeDelta;
double lonMax = region.center.longitude + .5 * startRegion.span.longitudeDelta;
Just remember that:
latitudeDelta
The amount of north-to-south distance (measured in degrees) to display on the map. Unlike longitudinal distances, which vary based on
the latitude, one degree of latitude is always approximately 111
kilometers (69 miles).
longitudeDelta
The amount of east-to-west distance (measured in degrees) to display for the map region. The number of kilometers spanned by a
longitude range varies based on the current latitude. For example, one
degree of longitude spans a distance of approximately 111 kilometers
(69 miles) at the equator but shrinks to 0 kilometers at the poles.

Related

convert Lat/Long to X,Y Coordinates in iOS [duplicate]

I am showing an image in an UIImageView and i'd like to convert coordinates to x/y values so i can show cities on this image.
This is what i tried based on my research:
CGFloat height = mapView.frame.size.height;
CGFloat width = mapView.frame.size.width;
int x = (int) ((width/360.0) * (180 + 8.242493)); // Mainz lon
int y = (int) ((height/180.0) * (90 - 49.993615)); // Mainz lat
NSLog(#"x: %i y: %i", x, y);
PinView *pinView = [[PinView alloc]initPinViewWithPoint:x andY:y];
[self.view addSubview:pinView];
which gives me 167 as x and y=104 but this example should have the values x=73 and y=294.
mapView is my UIImageView, just for clarification.
So my second try was to use the MKMapKit:
CLLocationCoordinate2D coord = CLLocationCoordinate2DMake(49.993615, 8.242493);
MKMapPoint point = MKMapPointForCoordinate(coord);
NSLog(#"x is %f and y is %f",point.x,point.y);
But this gives me some really strange values:
x = 140363776.241755 and y is 91045888.536491.
So do you have an idea what i have to do to get this working ?
Thanks so much!
To make this work you need to know 4 pieces of data:
Latitude and longitude of the top left corner of the image.
Latitude and longitude of the bottom right corner of the image.
Width and height of the image (in points).
Latitude and longitude of the data point.
With that info you can do the following:
// These should roughly box Germany - use the actual values appropriate to your image
double minLat = 54.8;
double minLong = 5.5;
double maxLat = 47.2;
double maxLong = 15.1;
// Map image size (in points)
CGSize mapSize = mapView.frame.size;
// Determine the map scale (points per degree)
double xScale = mapSize.width / (maxLong - minLong);
double yScale = mapSize.height / (maxLat - minLat);
// Latitude and longitude of city
double spotLat = 49.993615;
double spotLong = 8.242493;
// position of map image for point
CGFloat x = (spotLong - minLong) * xScale;
CGFloat y = (spotLat - minLat) * yScale;
If x or y are negative or greater than the image's size, then the point is off of the map.
This simple solution assumes the map image uses the basic cylindrical projection (Mercator) where all lines of latitude and longitude are straight lines.
Edit:
To convert an image point back to a coordinate, just reverse the calculation:
double pointLong = pointX / xScale + minLong;
double pointLat = pointY / yScale + minLat;
where pointX and pointY represent a point on the image in screen points. (0, 0) is the top left corner of the image.

Get distance between 2 latitude & longitude in iOS6+

I want to calculate the distance between 2 lat & long. I am able to calculate the distance as below
CLLocation *currentLoc = [[CLLocation alloc] initWithLatitude:-24.4132995 longitude:121.0790024];
CLLocation *restaurnatLoc = [[CLLocation alloc] initWithLatitude:-32.8310013 longitude:150.1390075];
CLLocationDistance meters = [restaurnatLoc distanceFromLocation:currentLoc];
NSLog(#"Distance between 2 geo cordinates: %.2f Meters",meters);
Now I want to get the direction from currentLocation to restaurnatLoc. For this I have below code
double DegreesToRadians(double degrees) {return degrees * M_PI / 180;};
double RadiansToDegrees(double radians) {return radians * 180/M_PI;};
-(double) bearingToLocationFromCoordinate:(CLLocation*)fromLoc toCoordinate:(CLLocation*)toLoc
{
double lat1 = DegreesToRadians(fromLoc.coordinate.latitude);
double lon1 = DegreesToRadians(fromLoc.coordinate.longitude);
double lat2 = DegreesToRadians(toLoc.coordinate.latitude);
double lon2 = DegreesToRadians(toLoc.coordinate.longitude);
double dLon = lon2 - lon1;
double y = sin(dLon) * cos(lat2);
double x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dLon);
double radiansBearing = atan2(y, x);
return RadiansToDegrees(radiansBearing);
}
It returns bearing = 114.975752 Now how can I decide whether restaurant is in North,South,West,East,NW,NE,SW,SE from my current location ?
I get 1 solution from this link Direction based off of 2 Lat,Long points But if I consider this solution , then I have doubt on bearing 114 from my location(red circle) to restaurant (green circle) as shown below. Correct me if I am wrong.
As current location is "Western Australia" & restaurant location is "Sydney" as shown in Google Maps.
Can any body tell me whats going wrong here ? Thanks.
///////////////////////////// Update /////////////////////////////
My compass diagram is wrong. Here is the correct diagram all thanks to AlexWien
Now I am getting the correct output
your compass rose is totally wrong. have you ever looked at a compass? open the iphone compass app and look where 90Degrees is located. It is east, not west like in your graphic.
geographical direction is measured clockwise!
so 114 deg is east, which matches you expectation

Finding Bounding Box from CLLocationCoordinate2D

I am working with an API that allows me to specify a "bounding box" of coordinate which allows me to only return results within that box:
Returns a list of geocaches inside the specified bounding box sorted
by the distance from the center of the box.
The parameters south
latitude, west longitude, north latitude, east longitude define the
edges of a bounding box.
Coordinates should be in decimal degrees Use
positive numbers for north latitude and east longitude and negative
numbers of south latitude and west longitude.
The box cannot cross
the 180° longitude line or the 90° or -90° points.
The math for this is a little beyond me, but I found somewhat helpful calculations, but I am not sure it is what I need for the API:
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(self.mapView.centerCoordinate, 2000.0, 2000.0);
CLLocationCoordinate2D northWestCorner, southEastCorner;
northWestCorner.latitude = center.latitude - (region.span.latitudeDelta / 2.0);
northWestCorner.longitude = center.longitude + (region.span.longitudeDelta / 2.0);
southEastCorner.latitude = center.latitude + (region.span.latitudeDelta / 2.0);
southEastCorner.longitude = center.longitude - (region.span.longitudeDelta / 2.0);
Does anyone know how I could do this? Are the calculations here not helpful in order to get the west longitude, north latitude, east longitude that define the edges of the bounding box?
EDIT:
The error I am getting:
Invalid value for parameter: bbox=south,west,north,east
Using the center value:
center=37.552821,-122.377413
Converted Box (after calculations from above):
bbox=37.561831,-122.388730,37.543811,-122.366096
Final Working code:
// Current distance
MKMapRect mRect = mapView.visibleMapRect;
MKMapPoint eastMapPoint = MKMapPointMake(MKMapRectGetMinX(mRect), MKMapRectGetMidY(mRect));
MKMapPoint westMapPoint = MKMapPointMake(MKMapRectGetMaxX(mRect), MKMapRectGetMidY(mRect));
CLLocationDistance distance = MKMetersBetweenMapPoints(eastMapPoint, westMapPoint);
// Region
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(request.center, distance, distance);
CLLocationCoordinate2D northWestCorner, southEastCorner;
northWestCorner.latitude = request.center.latitude + (region.span.latitudeDelta / 2.0);
northWestCorner.longitude = request.center.longitude - (region.span.longitudeDelta / 2.0);
southEastCorner.latitude = request.center.latitude - (region.span.latitudeDelta / 2.0);
southEastCorner.longitude = request.center.longitude + (region.span.longitudeDelta / 2.0);
base = [base stringByAppendingFormat:#"bbox=%f,%f,%f,%f&", southEastCorner.latitude,northWestCorner.longitude,northWestCorner.latitude,southEastCorner.longitude];
You seem to have gotten your hemispheres reversed. North and east are positive. So if you start from the center latitude and you want to find the northern boundary you ADD half the delta, not subtract.

Earth Latitude & Longitude to Latitude & Longitude on a 3D sphere

I have never done this sort of thing before,but what I am doing is making a 3D sphere (which has earth like texture) like shape where I want to plot locations onto it using the latitude and longitude from google maps of specific locations.Now I am wondering , my sphere radius is obviously smaller than earths radius, would this still effect the position of the latitude and longitude values to xyz given the following formula:
tx = radiusOfSphere * cos(latitude) * cos(longitude);
ty = radiusOfSphere * -sin(latitude);
tz = radiusOfSphere * cos(latitude) * sin(longitude);
Yes.
tx^2 + ty^2 + tz^2 = radius^2 & math = radius^2, so you are on your sphere.
if latitude=0, then ty = 0, so you are on a circle parallel to the equator.
if longitude=0, then tz = 0 so you are on the a meridian.
Just check that you are in xyz not xzy or zyx, and that North is x>0 and East y>0, or whatever signs are compatible with point of view of your 3D rendering soft.

How to calculate geography bounding box in iOS?

I'd like to make a Geographic Bounding box Calculation in iOS.
It can be aprox.
Input Parameters:
Current Location (Example: 41.145495, −73.994901)
Radius In Meters: (Example: 2000)
Required Output:
MinLong: (Example: 41.9995495)
MinLat: (Example: −74.004901)
MaxLong: (Example: 41.0005495)
MaxLat: (Example: −73.004901)
Requirement:
No Network Call
Any Ideas?
Mapkit / CoreLocation does not seem to offer this type of thing?
Any other Geographic SDK that i could use?
Thanks
I think you can use standard MapKit functions: MKCoordinateRegionMakeWithDistance, this will return a MKCoordinateRegion, which is really just a center point (lat, lon) and the spans in the latitudal and longitudal direction in degrees. Add/subtract half of the span from the latitude and longitude respectively and you have the values you're looking for.
CLLocationCoordinate2D centerCoord = CLLocationCoordinate2DMake(41.145495, −73.994901);
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(centerCoord, 2000, 2000);
double latMin = region.center.latitude - .5 * startRegion.span.latitudeDelta;
double latMax = region.center.latitude + .5 * startRegion.span.latitudeDelta;
double lonMin = region.center.longitude - .5 * startRegion.span.longitudeDelta;
double lonMax = region.center.longitude + .5 * startRegion.span.longitudeDelta;
By the way: this is only representative for the longitude for small spans, in the order of a couple of kilometers. To quote Apple:
latitudeDelta
The amount of north-to-south distance (measured in degrees) to use for the span. Unlike longitudinal distances, which vary based on the latitude, one degree of latitude is approximately 111 kilometers (69 miles) at all times.
longitudeDelta
The amount of east-to-west distance (measured in degrees) to use for the span. The number of kilometers spanned by a longitude range varies based on the current latitude. For example, one degree of longitude spans a distance of approximately 111 kilometers (69 miles) at the equator but shrinks to 0 kilometers at the poles.
I know I'm a bit late to the party, but I just built a class GTBoundingBox that might (or might not) help:
https://github.com/wpearse/ios-geotools

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