Absolute Accuracy, The Pier Stone
As usual another excellent publication, I especially like Marc’s comments related to Dr. Abdullah’s article and the need for the surveying community to come to grips about understanding positional accuracy. Marc knows this has been a soapbox issue of mine for years. I am hopeful that clearly written articles such as this one along with the forthcoming new geodetic and tidal datums and requirements from other geospatial related disciplines will help guide the community of surveying professionals into a better understanding of these issues.
Regarding Mr. Stocking’s “The Pier Stone, & Thomas Jefferson as the Geomancer in Chief “ (May/June 2024), I am always pleased to see an article on historical surveys and survey monuments, particularly involving our nation’s capital and the Jefferson Pier. I feel every surveyor should be familiar with this history. Several comments in Mr. Stocking’s article however require a bit of clarification. He states at the start that Thomas Jefferson personally performed the field work and calculations to establish the location of the Jefferson Pier (NGS PID UA0024). While it is certainly true that Jefferson ordered the establishment of a meridian marker that would define the longitude passing through the Presidents House (the White House) there is no evidence that he actually participated in any of the actual field work or computations. Jefferson drafted Issac Briggs, then recently appointed Surveyor General of the Mississippi Territory, who was assisted by Nicholas King Surveyor of the City to perform the work in 1804.
Mr. Stocking may be writing with tongue in cheek, but from the article he seems to believe that President Jefferson had some concept that this marker would be “the center of the globe.” I contend that there is absolutely no evidence that Jefferson harbored any such vision beyond that of a very practical surveyor and national leader who was already dealing with the fact that the fledgling country needed a structured framework to support the creation of vital nautical charts for safe commerce and travel as well as support for the National Land Ordnance which he had designed. There is no evidence in any of his efforts to create the Survey of the Coast (now the National Ocean Service) that his intentions were anything but an understanding that it was important for our nation to be scientifically as well as politically independent from Europe (Silvio Bedini, The Jefferson Stone, and referenced in the Wikipedia article Mr. Stocking cites). He understood there were already 16 national prime meridians that supported charting of those countries. Additionally, he never instigated any executive orders or national laws by congress to adopt the pier as the actual prime meridian of the United States. Regrettably there don’t seem to be any records indicating why he never moved forward, but my own suspicion is that he may have been convinced by some members of the American Philosophical Society not to, as all the other national prime meridians were directly related to sophistical observatories. No observatories existed in the U.S. at that time and did not in the city until the establishment of the Naval Observatory in Washington in 1839 about 4800 ft northwest of the location of the Pier.
One final point I would make is the 1912 official adoption of Greenwich as the meridian to be used by the United States following the International Meridian Conference which took place in Washington DC in 1884, none the less the Survey of the Coast, the agency responsible for the geodetic datums of the country’s maps and charts had defined longitude relative to Greenwich since the 1840s. It took several years for the various countries in attendance to each implement that consensus. And yes, it WAS a big deal.
Anyone interested in the Jefferson Pier and/or the nation’s capital boundary survey by Andrew Ellicott (Pierre L’Enfant doesn’t appear to have anything direct involvement with its design or implementation) should read the exceptionally well researched and respected works of Silvio Bedini who served as the Deputy Director of the Smithsonian’s National Museum of Natural History including; “The Jefferson Stone”, “With Compass and Chain” and “The Life of Benjamin Banneker” all of which are available from Amazon.
Respectfully submitted
Dave Doyle
Owner, Base 9 Geodetic Consulting Services
Errata
I cannot tell you how ironic it is to inform you that the article concerning Geospatial Mapping Accuracy has a very obvious mistake concerning an accuracy formula. Please look at the formula (Computing vertical accuracy) on page 31 of your current issue.
Later on the same page the author states:
“The value of 3.16 cm is the true vertical accuracy of the lidar dataset, versus the value of 1 cm derived by the mapping technique used commonly that ignores the errors introduced during the ground surveying process.”
Oops. Just goes to show how hard it really is to attain absolute accuracy.
Jack Chiles