Quick 1D X question

Just noticed a spring loaded oval door (tiny) on my camera and checked the manual and it is listed as "System extension mounting hole". That is all that it says!

What can be mounted here?

Curiosity has the better of me

Thanks.

It's aparently for a GPS/WiFi unit

I have a 1DX and it is NOT a spring loaded door, it is just a pull open door.

really? GPS?

This is not one of the large pull open doors, its a really smal 1/4 " oval door top left above the rubber pull open doors.

I believe the GPS/WiFi units have a little support stub that slides in that little hole.

It's on the 1D4 as well. (in a slightly different place)

I think it is just a place into which a mechanical pin goes, no electronic connection for the accessories to mount securely (GPS WiFi, but it's not to be confused with the electric connection port for the same accessories.

EDIT was typing as rdalrt was posting...

Thanks. You might be right. Here's a great picture of this little port:

https://canondslr1dx.f​iles.wordpress.com/201​3/03/image00001.jpg

That's where the pin of the GPS/wifi unit goes in to, so it springs out when you take it off

Precisely. Prevents torque inadvertently applied to the GP-E1/WFT-E6 to be transferred to the fragile connector. The pin absorbs the force instead.

Wait, how would this hole not be both the mechanical and electronic connection for the GPS/WiFi unit? The 1D (and 5D) series cameras don't have GPS/WiFi internally because their bodies are metal all the way around (and are completely shielded from EM waves). You have to buy a GPS/WiFi unit seperately (which going by the picture, you see those tiny little holes for connection pins).

I'm not sure why Canon doesn't make the 1D have at least a small area of the body plastic (and where GPS and WiFi antenae can go). Guess they believe it's too much of a comprimise in sealing....or they just want you to buy another accessory

Edit: OK, I see two pins: one just plastic for stabilizing(purely mechanical), the other is both mechanical and electric. So in regards to holes on the body...I think some of the confusion is which hole is being asked about: one is just a hole, the other is the connection.

In this case the question was about the "hole only", above the connector.
Putting the WiFi or GPS antenna in the accessory does of course give much better conditions for good radio performance than stowing it under a plastic little "window" in the camera's body.

But Canon still does it with the 7D2. I don't think the "system extension" adapter would be able to draw that much power to be able to have much greater range then an internal WiFi (without comprimising battery life). Wonder if there have been any studies on that? I'm assuming Canon does that for the sealing.

It's not about the power, but about the antenna.