Need Help in saving Geotag info with photo on iOS4.1

Question

I am having major issues trying to save a photo to camera roll with geotag info on iOS4.1. I am using following ALAssetsLibrary API:

• (void)writeImageDataToSavedPhotosAlbum:(NSData *)imageData metadata:(NSDictionary *)metadata completionBlock:(ALAssetsLibraryWriteImageCompletionBlock)completionBlock

I have the GPS coordinates that i wish to save with the photo as an input. Unfortunately, there is no documentation or sample code that describes how to form the metadata NSDictionary that encapsulates the GPS coordinates. Can somebody post a sample code that is known to work ?

I have also tried using iPhone Exif library to save geo info in imageData rather than using metadata, but unfortunately iPhone Exif library is crashing. Any help is greatly appreciated.