Near the east equator, celestial objects move up in the sky.
The equatorial line itself is marked by a pole extending a short distance above and below ground (down to bedrock). The "Sunrise" achievement will be granted the first time a blockhead reaches this pole. The pole itself functions as a back wall, allowing the placement of ladders, light sources, and blocks.
The Sunrise Hat Of Fullness can be found at the top of the pole.