Site-lines used to measure the Himalayas

love this stuff
Thanks

That is beyond cool:-)

The network the British established from the south tip of India to Himalayas is mind boggling. Notice how they stayed out of Nepal. Very cool.

You guys should check out The Great Arc by John Keay. It has lots of good survey nerd detail about Mr. Everest and the triangulation across India. Amazon has used ones as low as $4 incl. shipping.

Mount Everest
Mount Everest, also known in Nepal as Sagarm?th? and in Tibet as Chomolungma, is Earth's highest mountain. It is located in the Mahalangur section of the Himalayas. Wikipedia
Elevation: 29,029' (8,848 m)
First ascent: May 29, 1953
Prominence: 29,029' (8,848 m)
First ascenders: Tenzing Norgay, Edmund Hillary
Mountain range: Himalayas, Mahalangur Himal

they were off by 27'- probably used the wrong geoid.

Would love to get a frame worthy copy of that map. Near and dear to my heart. Went to school and became interested in surveying in that part of the world.

:gammon:

I am only seeing one Baseline at the E'ly end of Triangle Network.
I would think they would have one on W'ly end as a "check" of some sort.
I'll bet all line directions were Astronomical shots too.
How many years did it take to do all this?
I gotta get that book mentioned here.

As told in the book, the triangulation work began in 1802 and continued until about 1875. The north-south net known as the Great Arc was completed in 1837, and the elevation of Mt. Everest was computed and re-checked by 1852. George Everest, the mountain's namesake, was a quarrelsome and difficult boss, but he and his fellow surveyors-general, with a staff of about 1000, got the job done under very tough conditions.

Here's a map from the book showing the overall triangulation network, and a book review that I wrote for our state society magazine.

Book Review:

The Great Arc: The Dramatic Tale of How India was Mapped and Everest was Named, by John Keay. New York, HarperCollins, 2000.

I came across this book in the course of doing research for a presentation to elementary students. Even second-graders have heard of Mt. Everest, and telling the story of how its height was measured was a way of introducing them to the subject of survey equipment and surveying techniques. The story was even more interesting than I expected. John Keay, the author of a dozen other books on historical subjects, has written a concise and readable history of the Survey of India, probably the greatest surveying project of the 19th century and remarkably advanced for its time.

Surveys and maps of the Indian subcontinent became important in the late 1700’s due to the expansion of British trade and conquest. Trade was in the hands of the East India Company, which functioned for all practical purposes as a subsidiary of the British government. Accumulating vast wealth from its trade monopoly, the Company was allowed to maintain its own armed forces, conquer territory, and collect local taxes. To do these things, maps were needed.

The first maps were made by traditional military methods, using compass, chain, odometer and clinometer, with scattered astronomical observations for control. No one was very happy with them. William Lambton, who arrived in India in 1796 as an army lieutenant, knew it was possible to establish better control by triangulation. Lambton had been stationed for 13 years in New Brunswick, Canada, doing cadastral surveys. During the long winters, he had evidently spent much of his time studying astronomy, geodesy, and mathematics. His zeal for astronomy was such that he was partially blind in his left eye, the result of taking a sun shot without an adequate filter. Aided by his friendship with Arthur Wellesley, later known as the Duke of Wellington, Lambton proposed a triangulation network beginning at Madras, near the southern tip of India. In 1800 his proposal was approved by the Company, and he set about acquiring suitable equipment.

Lambton’s first 7.5 mile baseline, near Madras, was measured in the spring of 1802 with a 100-foot chain consisting of 2.5-foot steel bars joined with brass hinges. Expansion due to temperature was a constant concern, and required laborious calibration and adjustments. To measure angles, he ordered from England an instrument that became known as the Great Theodolite, with a 36-inch horizontal circle. The ship carrying it was captured by the French, with whom England was then at war. But when the French realized what they had, they sent the instrument on to Madras, along with a polite note expressing their support for science.

From this baseline, Lambton’s first triangulation series extended southerly along the coast from Madras. Its purpose was to determine the local length of a degree of latitude, needed for preliminary correction factors to adjust the trigonometry for the curvature of the earth. He then ran a chain of triangles westerly from Madras, and began a north-south series following the 78th meridian of East longitude, a part of what was later known as the Great Arc.

Lambton had originally planned to extend the Arc through two or three degrees of latitude. But he and his assistant, George Everest (he pronounced his name “eve-rest”) soon became obsessed with the idea of triangulating from the extreme southern tip of India to the foothills of the Himalayas, over 20 degrees of latitude and a distance of about 1600 miles. This network, along with other triangulation, would of course provide control for the local surveys and topographic maps that the Company wanted. But it would also measure the earth’s curvature, in the southern hemisphere, far more accurately than anyone had previously done. To complete the Great Arc, both Lambton and Everest had to spend some of their time placating Company officials, who wanted local maps as the first priority and had little interest in geodesy.

Everest began work with the Survey in 1818, and succeeded Lambton when the latter died of fever in early 1823. He introduced many improved methods. He originated the practice of making night observations to lighted signals, and that of running chains of triangles in a grid rather than covering the entire country with stations. For work in flat terrain, he designed a double tower, with independent support for the instrument, on the same principle as the Bilby towers used in modern times. These towers, built of timber and bamboo, proved less stable that he had hoped when loaded with the 1000-pound Great Theodolite. In the end, in areas where no hills or mountains were available, Everest used the timber towers for preliminary triangulation but had 60-foot brick towers built for the final observations

It would be hard to overstate the practical difficulties of carrying on the Survey. Dense jungles, suspicious natives, and monsoon rains slowed the field work. Many desirable hilltop locations for triangulation stations were occupied by bands of armed men, loyal to local rulers. Tigers stalked the crews. In 1808 the Great Theodolite was dropped and badly damaged while it was being hoisted to an observation point atop a 200-foot temple; Lambton spent six weeks repairing it with the aid of his head instrument maker. Malaria and other tropical diseases took hundreds of lives. Everest had to leave India for five years to recover his health. He spent the time productively by re-working his calculations, lobbying for financial support, and acquiring new equipment, returning with a set of temperature-compensating bars for measuring baselines.

Everest retired in 1843, with the Great Arc completed. In addition to surveying the Arc, he and his successor, A. S. Waugh, covered most of India with a triangulation grid. From the northerly stations, vertical and horizontal angles were read to Himalayan mountain peaks, some over 100 miles away. In 1856 Waugh reported that the summit designated as “Peak XV” might well be the world’s highest, and proposed naming it for Everest. The name stuck, despite some argument. It seems unlikely that Everest himself ever saw the mountain.

Since the book was written for a general audience, it contains less technical detail than a surveyor might prefer. I would have been interested in knowing more about the Great Theodolite and other equipment used; and more maps, of higher quality, would have been desirable. But it is nevertheless valuable historical background for surveyors. And members of the public are likely to be impressed by the little-known story of how surveyors discovered the world’s highest mountain, and how it was named for one of them.