It appears that about half of the Chinese pyramids visible on Google Earth are aligned ten degrees East of true North.

While half of them are aligned with what we know today as true North (or to pilots, 090), the other half are aligned with 080.

How long ago did true North change?  Since Dangun's Pyramid is aligned with true North now, it must have been built much

later than these misaligned Chinese pyramids were.

Sanseongha Tomb Complex

http://www.goguryeo.org/photos/p_tomb_sanseongha.php  

http://www.astro.uiuc.edu/~kaler/sow/thuban.html

THUBAN (Alpha Draconis). Fourth magnitude (though just barely) Thuban is one of the fainter stars that carries a proper name, almost certainly because of its immense historical role as a result of its position in the northern sky. Its importance is further highlighted in that it is the Alpha star of Draco (the Dragon) even though it not close to being the brightest of this long and rambling constellation, easily exceeded in visibility by Gamma, Beta, and even Eta Draconis. Among the most famed stars of the sky is Polaris, the north star, its prominence the result of its position close to the north celestial pole, the star showing the way north to within about half a degree. It was not always so, however. The Earth's rotational axis undergoes a slow, 26,000 year wobble around the perpendicular to its orbit around the Sun. As a result, the position of the sky's rotational pole, around which all the stars seem to go, constantly changes. Around the time of the Greek poet Homer, Kochab in Ursa Minor was a (rather poor) pole star. Among the best ever, however, was our Thuban, which was almost exactly at the pole in 2700 BC. It remained better than Kochab up to around 1900 BC, and was therefore the pole star during the time of the ancient Egyptian civilizations. Even though the star is in the Dragon's tail, its name confusingly derives from an Arabic phrase meaning "the Serpent's head," having been borrowed from the name for another star. Thuban is among a fairly rare class of hot giant stars, its temperature of 9800 Kelvin near that of Vega. It is, however, over five times as luminous as Vega (and 300 times more luminous than the Sun), its fourth magnitude status the result of its rather large distance of 310 light years. Its relative brightness tells us that the star, unlike Vega, has ceased hydrogen fusion in its core and has begun to die. Thuban has an faint unseen companion in an orbit with a 51 day period and, unlike many stars of its class, has no particular abundance anomalies. It is in fact somewhat poor in metals as compared with the Sun.

http://www.americanscientist.org/template/AssetDetail/assetid/35115?&print=yes

A long–standing problem relating not only to the Great Pyramid but also its smaller cousins is the question of how the builders managed to orient such colossal structures to the cardinal points with surprisingly high accuracy. The eastern side of the Great Pyramid, for example, points only three arcminutes away from a true north–south line, and other pyramids in the group are not much worse. This makes it virtually certain that some astronomical method was used to establish the local meridian. At first thought this does not seem too difficult a problem, even without a bright star close to the north celestial pole during the millennia of interest. (Even today, Polaris is some 43 arcminutes from the pole, and during this time it was about 25 degrees away.)

http://www.bautforum.com/general-science/56761-great-pyramid-alignment-question.html

No, it was not close enough. Polaris was as much as 25° away from the celestial pole at the time. The nearest bright star was Draco's Thuban (see this image).

And why would they have used Polaris? Kochab (Beta UMi) has almost the same brightness and it was much closer to the pole.

http://interoz.com/EGYPT/cheops.htm