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The ascending passage adjustment

The geometric ascending passage line is highlighted in the drawing with its angle of 26° 1' 34.01" showing the discrepancy from Smyth's surveying measurement of 0° 5' 6.02", with the polar cross section of the Earth and the equator shown as a horizontal line. This is exactly the same construction as on the previous page (page B6) but with the principal ellipse added to the drawing.

If the cross section of the Earth is now rotated by the angle of its fixed axial tilt, 23.43906498°, the value of which is taken from the NASA DE431 ephemeris, then the ascending passage line's angle will be altered because its formation geometry is altered.

Keep your eye on the ascending passage angle in the object information panel and click here to apply this fixed axial tilt g.geoid.axialTilt rotation and you can see that the geometric line which forms the ascending passage now has a discrepancy to the surveying of 0° 0' 10.36" which equates to a realistic linear surveying accuracy of 2mm along the length of the ascending passage line.

The surveyed angle of the ascending passage has a value of 26° 6' 40" as measured by Smyth (Page 151, table 1) from the gallery down to the plug blocks. This differs from the angle that Petrie reports of 26° 2' 30" which is the average angle of the passage from its start point in the entrance passage, the angle of the plug block section having been calculated by Petrie as having a steeper angle of 26° 12' 30" along the length of the first 300 inches of the ascending passage.

Therefore, in the basic section, the constructed ascending passage is formed from an astronomically accurate rotated polar cross section of the Earth.

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Last edited: 20th September 2019