http://www.usa.canon.com/cusa/support/professional/professional_cameras/gps_receivers/gps_receiver_gp_e2?pageKeyCode=writeReviewPage
GPS Receiver GP-E2
24468

Features
When in use, the GPS Receiver GP-E2* will automatically record the geographical information (latitude, longitude, altitude, and Universal Coordinated Time (UTC)) of videos and photos. Detecting altitude is even possible from inside an airplane or helicopter.
*In certain countries and regions, the use of GPS may be restricted. Therefore, be sure to use GPS in accordance with the laws and regulations of your country or region. Be particularly careful when traveling outside your home country.
As a signal is received from GPS satellites, take sufficient measures when using in locations where the use of electronics is regulated.
GPS Receiver GP-E2
5
5
2
2
Truly recommend it
The receiver looks like a small space starship once mounted on my Canon 5D Mark III. Works nicely and easily. Sometimes connecting to the GPS takes 2-3 minutes, but cannot indicate in which conditions it is much slower than the norm. Having pictures tagged with all coordinates is a very nice feature to have, primarily went in urban areas or in the wilderness. Actually, it is useful everywhere. Always travel with spare batteries just in case. Forgot to turn it off only the first time: lesson learnt.
May 18, 2013
Very accurate
Used in various places around the world. Match perfectly position as Google Earth, etc. As long in direct view of satellites extremely accurate. That.s not the case of cities where high buildings reduce the "access" to satellites signals resulting in some errors - applicable to any GPS receiver anyhow. Very satisfied about it!
October 9, 2012
