6. The imaginary central vertical line in hau tea does correspond to an imaginary line on Easter Island. As has been suggested the vertical line at right in the glyph probably represents the horizon in the east and the vertical line at left the horizon in the west, while the central one cannot be a horizon - there is no more parallel horizon:

Instead the central line is imaginary - shown by it being a separate element not connected with the rest of the glyph.

The center of the island is Anakena with the king. As noted in Barthel 2, also Vinapu is located in the middle, and an imaginary line can be drawn between these two central places:

'... On the 'second list of place names', Hanga Te Pau is called 'the middle (zenith) of the land' (he tini o te kainga). This may refer to a line bisecting the island... Vinapu and Anakena were calendary opposites ...'

Astronomers observe stars rising in the east and setting in the west, but they also observe them when they are passing right overhead. A kind of structure with 3 parallel lines is used for observing stars.

Hamlet's Mill:

"It should be stated right now that 'fire' is actually a great circle reaching from the North Pole of the celestial sphere to its South Pole ..."

At noon sun stands high and blazing, and the great 'fire' circle noted in Hamlet's Mill presumably is equal to the imaginary line through Anakena southwards to Vinapu. Sun moves from east to west, but the imaginary line is oriented the other way, from north to south, and therefore it is a line marking time and a line connected with the moon. The name hau tea is quite in order, it is primarily a female glyph type, a glyph type for housing new life.