With the lower chamber completed the essential understanding that the 1:87500 model of the Earth that forms the pyramid's architecture is a model of the Earth when it is located at a distance of 1 AU from the Sun has been obtained. Also, the master ellipse of the lower chamber is a derivation of the geometry placed relative to sea level rather than being an integral part of the that geometry, and so the final master ellipse can now be created directly within the geometry.
What is required is a model of the Earth that needs to grow in size relative to the 1 AU model as the Earth approaches Perihelion and shrinks in size relative to the 1 AU model as the Earth approaches Aphelion. This being the case, then it will form a visual model of the Earth as viewed from the Sun and must therefore have its center point fixed to the center of the geometry of the building.
If you start the clock you can see exactly this construction on the interactive drawing with the master ellipse centered on the middle of the building's vertical axis, and the model of the Earth shrinking and growing during its orbit, passing through the distance of 1 AU from the Sun at which point the drawing is scaled to 1:87500.
Once the concepts of this visual model of the Earth have been formed they can be used to get into the main chamber of the building via the 'horizontal' passage that leads from the top of the gallery. This passage runs into the antechamber which is the name given to the small room which splits the main chamber passage into two parts and can be seen in more detail by zooming in on it.
Up to this point in the work the Earth's equator has been shown as just part of the graphics of the Earth but now, rather than just drawing the equator onto the ellipse, it can be added as a geometric object. You can zoom out again and display the Earth's equator as a geometric object.
The lower turning point of the equator ellipse which runs through the antechamber passage is being plotted out over time and because this point is being formed from the master ellipse, which is shrinking and growing in size, the plotted equator turning point does not form a horizontal line as would have been the case if the Earth remained the same size during its orbit. Instead it is plotting out the very flattened yellow ellipse and if you zoom back in to the antechamber and let the plot develop you can see that there are two yellow lines being plotted across the antechamber.
These two lines, the upper and lower parts of the elongated yellow equator turning point ellipse, are the same vertical distance apart as the roof area of the antechamber and this is not coincidental. They are the geometric lines which should form that roof section.
If you stop the clock and display an explanatory drawing you can see that the distance between the yellow lines defines the antechamber's roof height. The reason that the yellow geometry lines do not match up with the roof lines is that the Z-axis rotation needs to be applied to the geometry system at this stage, which makes a significant difference to the vertical positioning of any elements within the geometry.
You cannot progress any further down the antechamber passage without applying the Z-axis rotation to the Earth's ellipsoid.