Flickr APIを使って、写真のGPS情報を取得するには「flickr.photos.getExif」APIを使います。

flickr.photos.getExifからのレスポンス

<rsp stat="ok">
  <photo id="12499156243" secret="170c8d62c6" server="7419" farm="8" camera="Apple iPhone 5s">
    <exif tagspace="IFD0" tagspaceid="0" tag="Make" label="Make">
      <raw>Apple</raw>
    </exif>
    <exif tagspace="IFD0" tagspaceid="0" tag="Model" label="Model">
      <raw>iPhone 5s</raw>
    </exif>
    <exif tagspace="IFD0" tagspaceid="0" tag="Orientation" label="Orientation">
      <raw>Rotate 90 CW</raw>
    </exif>
	   ・
	   ・
	   ・
  </photo>
</rsp>

このExif情報を使ってアプリ側で何かしたい場合は、
上記のflickrから返ってくるレスポンスとiOS側でExifを扱う定数を紐付ける必要があります。

以下は、その一部です。
Exif情報を取得した写真はiPhone5Sで撮影したものです。
撮影したカメラや撮影時の環境でレスポンスの内容は変わります。

flickr(tagspace)	flickr(tag)	flickr(label)	iOS
IFD0	Make	Make	kCGImagePropertyTIFFMake
IFD0	Model	Model	kCGImagePropertyTIFFModel
IFD0	Orientation	Orientation	kCGImagePropertyTIFFOrientation
IFD0	XResolution	X-Resolution	kCGImagePropertyTIFFXResolution
IFD0	YResolution	Y-Resolution	kCGImagePropertyTIFFYResolution
IFD0	ResolutionUnit	ResolutionUnit	kCGImagePropertyTIFFResolutionUnit
IFD0	Software	Software	kCGImagePropertyTIFFSoftware
IFD0	ModifyDate	Date and Time (Modified)	kCGImagePropertyTIFFDateTime
IFD0	YCbCrPositioning	YCbCr Positioning	?
IFD1	Compression	Compression	kCGImagePropertyTIFFCompression
IFD1	ResolutionUnit	Resolution Unit	kCGImagePropertyTIFFResolutionUnit
IFD1	ThumbnailOffset	Thumbnail Offset	?
IFD1	ThumbnailLength	Thumbnail Length	?
ExifIFD	ExposureTime	Exposure	kCGImagePropertyExifExposureTime
ExifIFD	FNumber	Aperture	kCGImagePropertyExifFNumber
ExifIFD	ExposureProgram	ExposureProgram	kCGImagePropertyExifExposureProgram
ExifIFD	ISO	ISO Speed	kCGImagePropertyExifISOSpeedRatings
ExifIFD	ExifVersion	Exif Version	kCGImagePropertyExifVersion
ExifIFD	DateTimeOriginal	Date and Time (Original)	kCGImagePropertyExifDateTimeOriginal
ExifIFD	CreateDate	Date and Time (Digitized)	kCGImagePropertyExifDateTimeDigitized
ExifIFD	ComponentsConfiguration	Components Configuration	kCGImagePropertyExifComponentsConfiguration
ExifIFD	BrightnessValue	Brightness Value	kCGImagePropertyExifBrightnessValue
ExifIFD	MeteringMode	Metering Mode	kCGImagePropertyExifMeteringMode
ExifIFD	Flash	Flash	kCGImagePropertyExifFlash
ExifIFD	FocalLength	Focal Length	kCGImagePropertyExifFocalLength
ExifIFD	SubjectArea	Subject Area	kCGImagePropertyExifSubjectArea
ExifIFD	SubSecTimeOriginal	Sub Sec Time Original	kCGImagePropertyExifSubsecTimeOrginal
ExifIFD	SubSecTimeDigitized	Sub Sec Time Digitized	kCGImagePropertyExifSubsecTime or kCGImagePropertyExifSubsecTimeDigitized
ExifIFD	FlashpixVersion	Flashpix Version	kCGImagePropertyExifFlashPixVersion
ExifIFD	ColorSpace	Color Space	kCGImagePropertyExifColorSpace
ExifIFD	SensingMethod	Sensing Method	kCGImagePropertyExifSensingMethod
ExifIFD	SceneType	Scene Type	kCGImagePropertyExifSceneType
ExifIFD	ExposureMode	Exposure Mode	kCGImagePropertyExifExposureMode
ExifIFD	WhiteBalance	White Balance	kCGImagePropertyExifWhiteBalance
ExifIFD	DigitalZoomRatio	Digital Zoom Ratio	kCGImagePropertyExifDigitalZoomRatio
ExifIFD	FocalLengthIn35mmFormat	Focal Length (35mm format)	kCGImagePropertyExifFocalLenIn35mmFilm
ExifIFD	SceneCaptureType	Scene Capture Type	kCGImagePropertyExifSceneCaptureType
ExifIFD	LensInfo	Lens Info	kCGImagePropertyExifLensSpecification
ExifIFD	LensMake	Lens Make	kCGImagePropertyExifLensMake
ExifIFD	LensModel	Lens Model	kCGImagePropertyExifLensModel
GPS	GPSLatitudeRef	GPS Latitude Ref	kCGImagePropertyGPSLatitudeRef
GPS	GPSLatitude	GPS Latitude	kCGImagePropertyGPSLatitude
GPS	GPSLongitudeRef	GPS Longitude Ref	kCGImagePropertyGPSLongitudeRef
GPS	GPSLongitude	GPS Longitude	kCGImagePropertyGPSLongitude
GPS	GPSAltitudeRef	GPS Altitude Ref	kCGImagePropertyGPSAltitudeRef
GPS	GPSAltitude	GPS Altitude	kCGImagePropertyGPSAltitude
GPS	GPSTimeStamp	GPS Time Stamp	kCGImagePropertyGPSTimeStamp
GPS	GPSImgDirectionRef	GPS Img Direction Ref	kCGImagePropertyGPSImgDirectionRef
GPS	GPSImgDirection	GPS Img Direction	kCGImagePropertyGPSImgDirection
GPS	GPSImgDirection	GPS Img Direction	kCGImagePropertyGPSImgDirection