Converting a string to double for coordinate use, Xcode - objective-c

Question

I have a list of longitudes and latitudes in an XML file. I can print the lat and lon as a string but when i convert the string to a double i get 0.
Here is my code:
NSString *latstring = [[NSString alloc] initWithString:theList.lat] ;
NSString *lonstring = [[NSString alloc] initWithString:theList.lon];
NSLog(#"latstring: %#, lonstring: %#", latstring, lonstring);
double latdouble = [latstring doubleValue];
double londouble = [lonstring doubleValue];
NSLog(#"latdouble: %g, londouble: %g", latdouble, londouble);
When i log 'latstring' and 'lonstring' i get the correct coordinates however when i log 'latdouble' and 'londouble' i get 0.
I need the lat and lon values as double so i can use them in a mapview as it will not allow me to use a string for the coordinates.
There is probably a very simple explanation for this however i am fairly new to objective-c and cant seem to find a solution for this.
Any help is much appreciated.

Answer 1

Solved the issue. After counting the length of the strings like Phillip said to do it turned out the length was 1 character longer than the string. So i added another string in-between that was the same string as 'latstring' and 'lonstring' however it began at index 1 rather than 0, therefore cutting off whatever character must have been infront of the coordinate value. This then converted to double perfectly.
Here is the code is used:
NSString *latstring = theList.lat;
NSString *lonstring = theList.lon;
NSLog(#"%#, %# wooo", latstring, lonstring);
NSString *latcutstring = [latstring substringFromIndex:1];
NSLog(#"cut lat: %#", latcutstring);
NSString *loncutstring = [lonstring substringFromIndex:1];
NSLog(#"cut lon: %#", loncutstring);
double latdouble = [latcutstring doubleValue];
NSLog(#"latdouble: %f", latdouble);
double londouble = [loncutstring doubleValue];
NSLog(#"londouble: %f", londouble);
Thankyou Phillip Mills and Tobol for you're help.
EDIT: Nov 2012
It was white space causing problems and i have found a safer way of doing this as to not cut out needed characters, as craig and phillip said.
NSString *trimlat = [theList.lat stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSString *trimlon = [theList.lon stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
//Convert to double
double latdouble = [trimlat doubleValue];
double londouble = [trimlon doubleValue];
//Create coordinate
CLLocationCoordinate2D coord = {(latdouble),(londouble)};

Answer 2

I think those strings aren't formatter well. there can't be anything else than whitespace before the number. The lat and lon has to be in format like as 'dd.ddddddd'.
NSString *works = #" 12.5431 jdty";
NSString *doesntWorks = #"E 43.4345";
NSString *latstring = [[NSString alloc] initWithString:works] ;
NSString *lonstring = [[NSString alloc] initWithString:doesntWorks];
NSLog(#"latstring: %#, lonstring: %#", latstring, lonstring);
double latdouble = [latstring doubleValue];
double londouble = [lonstring doubleValue];
NSLog(#"latdouble: %g, londouble: %g", latdouble, londouble);