Amidst the high desert landscape of the American Southwest is the unique Four Corners landmark, where a monument marks the intersection of Colorado, New Mexico, Arizona, and Utah. This location is the only point in the United States where four states touch. It is a must-see destination for many visitors, a place where feet and hands can each be in a different state and families and friends can straddle the disk marking the precise location where state boundaries meet. The original surveyor, Chandler Robbins, marked the spot with a 2.1-m (7-ft) sandstone monument in 1875. The present monument and visitor plaza date to 1992 and are owned and operated by the Navajo Nation Parks and Recreation Department.
In the spring of 2009, news reports claimed that the location of Four Corners was in error, that in fact the monument was located 4 km (2.5 mi) west of the precise location. The reports claimed that new surveys by the National Geodetic Survey (NGS) using the satellite Global Positioning System (GPS) and state of the art mapping technology refuted the original 1875 surveys. For such an important landmark, this was shocking news. Did the monument now need to be moved, or was the news in error?
For the average visitor, such precise measurement details are unimportant. For the scientist, engineer, or natural resource professional, such an error has wide-ranging implications. Four Corners is an established benchmark in the western United States upon which other surveys and locations are based.
The question of accuracy relates to which meridian was used for the original survey. Congress ordered Chandler Robbins in 1875 to use the Greenwich meridian, London, which later became the official 0° prime meridian, from which we measure longitude west or east on Earth. However, in the late 1800s, many western states were set with surveys using the Washington meridian, which is about 77° 3′ west longitude from Greenwich. If Robbins’ survey had used the Washington meridian, the
marker would be off, as described by the media reports.
A few weeks later the news stories were corrected as the details of the original survey came to light. While the monument does appear to be offset from its intended location, the actual offset is only 548 m (1800 ft) to the east rather than west. However, according to NGS, the monument is in the right spot. It turns out that the location of a physical monument is usually the ultimate authority in delineating a boundary.
In the spring of 2009, news reports claimed that the location of Four Corners was in error, that in fact the monument was located 4 km (2.5 mi) west of the precise location. The reports claimed that new surveys by the National Geodetic Survey (NGS) using the satellite Global Positioning System (GPS) and state of the art mapping technology refuted the original 1875 surveys. For such an important landmark, this was shocking news. Did the monument now need to be moved, or was the news in error?
For the average visitor, such precise measurement details are unimportant. For the scientist, engineer, or natural resource professional, such an error has wide-ranging implications. Four Corners is an established benchmark in the western United States upon which other surveys and locations are based.
The question of accuracy relates to which meridian was used for the original survey. Congress ordered Chandler Robbins in 1875 to use the Greenwich meridian, London, which later became the official 0° prime meridian, from which we measure longitude west or east on Earth. However, in the late 1800s, many western states were set with surveys using the Washington meridian, which is about 77° 3′ west longitude from Greenwich. If Robbins’ survey had used the Washington meridian, the
marker would be off, as described by the media reports.
A few weeks later the news stories were corrected as the details of the original survey came to light. While the monument does appear to be offset from its intended location, the actual offset is only 548 m (1800 ft) to the east rather than west. However, according to NGS, the monument is in the right spot. It turns out that the location of a physical monument is usually the ultimate authority in delineating a boundary.
Thus, once the Four Corners monument was established and accepted by all parties involved in this case, the four territories and the U.S. Congress it became the exact spot where the four states meet. The location, set for more than 125 years, is used in the modern National Spatial Reference System and is in the right place 36° 59′ 56.3150 north latitude by 109° 02′ 42.6210 west longitude.