I haven't heard the word "GeoTag" before, but I know Exif supports a whole lot of GPS tags.
http://www.exif.org/Exif2-2.PDF"In addition to the attribute information indicated as mandatory in the TIFF standard, this Exif
standard adds the TIFF optional tags that can be used in a DSC or other system, Exif-specific tags for recording
DSC-specific attribute information, and GPS tags for recording position information."
These GPS tags are stored the same way as Exif tags, i.e. it wouldn't be hard to implement insertion/extraction of these tags.
GPS tag version - GPSVersionID
North or South Latitude - GPSLatitudeRef
Latitude - GPSLatitude
East or West Longitude - GPSLongitudeRef
Longitude - GPSLongitude
Altitude reference - GPSAltitudeRef
Altitude - GPSAltitude
GPS time (atomic clock) - GPSTimeStamp
GPS satellites used for measurement - GPSSatellites
GPS receiver status - GPSStatus
GPS measurement mode - GPSMeasureMode
Measurement precision - GPSDOP
Speed unit - GPSSpeedRef
Speed of GPS receiver - GPSSpeed
Reference for direction of movement - GPSTrackRef
Direction of movement - GPSTrack
Reference for direction of image - GPSImgDirectionRef
Direction of image - GPSImgDirection
Geodetic survey data used - GPSMapDatum
Reference for latitude of destination - GPSDestLatitudeRef
Latitude of destination - GPSDestLatitude
Reference for longitude of destination - GPSDestLongitudeRef
Longitude of destination - GPSDestLongitude
Reference for bearing of destination - GPSDestBearingRef
Bearing of destination - GPSDestBearing
Reference for distance to destination - GPSDestDistanceRef
Distance to destination - GPSDestDistance
Name of GPS processing method - GPSProcessingMethod
Name of GPS area - GPSAreaInformation
GPS date - GPSDateStamp
GPS differential correction - GPSDifferential