IT is stargate-esque, but basically on a smaller scale. Since I don't see it becoming relevant at any point, and you have now seen where it is you ended up, I'll explain this bit of technology the way I envision it.
Note: if you haven't read my game post, do that first before continuing.
What you passes through amounts to a teleporter. The technology has it's limitations, however. The farther you transport the object, the more power it takes. The practical limit for the technology is about the distance between the earth and the sun, so it's no good for interstellar travel, or really even direct interplanetary travel within a solar system. Something like that would take a system of relay stations where you would switch from one teleporter to the next until you get to your destination.
A linked pair of portals is not required, (as you discovered) but it is much more efficient to do so in both time and power, since it takes quite a while to set a portals location when there is not a portal built as an anchor point.
Long story short, you're still on earth, and you used a lot of power to get to your new location.
By the way, the coordinates are in the Brazilian rainforest just north of the amazon river, to save you the trouble of looking them up. but if you do look them up on google earth or google maps, you'll see that there is actually the clearing at those coordinates, and the "grassy road" does go south east.