original image by Glen Dash 26FEB18 Modified
In 1874, David Gill participated in Lord Lindsay’s transit of Venus operation. On his way home he met with the Khedive of Egypt to discuss a projected survey of the country. While at Giza, he erected the wooden mast whose top established the original height of Khufu’s Great Pyramid. In 2018, the Journal of the History of Astronomy, Vol. 49(1) 3-26 published:
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”Gill spent some four months in Egypt on his survey work. About his survey of the great pyramid, the noted Egyptologist Flinders Petrie, who had been involved in the reduction of Gill’s measurements, said “this far surpassed all previous work in its accuracy”. Gill placed small survey markers on the bedrock by the corners of the great pyramid that he surveyed to an accuracy of 1 mm. These are still in use. He also boldly installed a survey post at the very top of the only surviving ‘great wonder’ of the ancient world – a memorial to David Gill seen by a great many tourists with sharp eyes.”
Dr. Troglodyte