Calculating driving distance to a particular coordinate - iphone

Question

Is there a way where i could get the driving distance to a particular geo-cordinate ? I am aware that i have to use http://maps.googleapis.com/maps/api/directions/output?parameters and get a JSON output to get the results.
Is there a tutorial that explains how to get this done? or any sample code where i start on?

Answer 1

You may try the following. This code fetches all directions (even the alternate ones) returned by Google Directions Services. You can get the distance in step 2 (parsing response)
Step 1: Enter the From and To Locations
NSMutableString *googleURL = [[NSMutableString alloc] initWithString:[NSString stringWithFormat:#"http://maps.googleapis.com/maps/api/directions/json?origin=%#&destination=%#&sensor=true&alternatives=true", searchFrom.text, searchTo.text]];
NSURL *url = [NSURL URLWithString:googleURL];
[googleURL release];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[NSURLConnection connectionWithRequest:request delegate:self];
request = nil;
responseData = [[NSMutableData alloc] init];
Step 2: When you get the response of the query made, parse the result
- (id)parseResponseWithDictionary:(NSDictionary *)dictResponse {
if ([[dictResponse objectForKey:#"status"] isEqualToString:kGoogleDirectionsStatusOK]) {
NSArray *listRoutes = (NSArray *)[dictResponse objectForKey:#"routes"];
NSMutableString *result = nil;
NSMutableArray *listPolylines = nil;
for (NSDictionary *dictRouteValues in listRoutes) {
NSDictionary *dictPolyline = [dictRouteValues objectForKey:#"overview_polyline"];
if (!result) {
result = [[NSMutableString alloc] init];
}
[result appendString:[dictPolyline objectForKey:#"points"]];
if (!listPolylines) {
listPolylines = [[NSMutableArray alloc] init];
}
[listPolylines addObject:result];
[result release];
result = nil;
}
return [listPolylines autorelease];
}
else {
NSString *error = #"No result found. Please check start and end location again!";
return error;
}
return nil;
}
Step 3: Decode each polyline in the polyline list. This will give the path coordinates.
-(NSMutableArray *)decodePolyLine:(NSMutableString *)encoded {
[encoded replaceOccurrencesOfString:#"\\\\" withString:#"\\"
options:NSLiteralSearch
range:NSMakeRange(0, [encoded length])];
NSInteger len = [encoded length];
NSInteger index = 0;
NSMutableArray *listCoordinates = [[[NSMutableArray alloc] init] autorelease];
NSInteger lat=0;
NSInteger lng=0;
while (index < len) {
NSInteger b;
NSInteger shift = 0;
NSInteger result = 0;
do {
b = [encoded characterAtIndex:index++] - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
NSInteger dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = [encoded characterAtIndex:index++] - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
NSInteger dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
lng += dlng;
NSNumber *latitude = [[NSNumber alloc] initWithFloat:lat * 1e-5];
NSNumber *longitude = [[NSNumber alloc] initWithFloat:lng * 1e-5];
//CLLocation *loc = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]];
[listCoordinates addObject:[NSString stringWithFormat:#"%f,%f", [latitude floatValue], [longitude floatValue]]];
//[loc release];
[latitude release];
[longitude release];
}
return listCoordinates;
}

Answer 2

this newer tutorial/sample code using CoreLocation and MapKit helped me a bunch.