** Wild speculation and I apologize if this has been brought up, previously **
A thread posted, tonight, by Rachda (http://carnage.bungie.org/haloforum/halo.forum.pl?read=706856) caused me to ponder Astro the Space Duck's glyph documentation (http://halosm.bungie.org/story/forerunner/jsymbols.html). The glyph indicated by Rachda possibly indicates the location of the Ark, or Installation 0, 00 or 0,0. That glyph's 'observer circle' appears in quadrant I. If that glyph is then rotated through the remaining 270 degrees of the circle, the 'observer circle' appears in each remaining quadrant. This is also true of the glyph that appears to be, for lack of a better term, a lock.
These glyphs appear in blue and red in Halo, suggesting 'benign' and 'warning' or 'danger' to me. I was never quite able to put that red glyph into words, until tonight. Rachda's posts helped me apply the word 'lock' to that glyph.
I wrote up the document, below, tonight. Unfortunately two of the glyph images freaked out.