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Home arrow Archives   The American Surveyor     

True Elevation: Black Elk Peak Print E-mail
Written by Jerry Penry, PS   
Sunday, 23 April 2017

A 5.000Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Black Elk Peak, located in the Black Hills region of South Dakota, is the state's highest natural point. It is frequently referred to as the highest summit in the United States east of the Rocky Mountains. Two other peaks, Guadalupe Peak in Texas and Sierra Blanca Peak in New Mexico, are higher and also east of the Continental Divide, but they are considered south of the Rockies.

The famed Black Elk Peak was known as Harney Peak as early as 1855 in honor of General William S. Harney. This designation lasted for more than 160 years, but the peak was renamed Black Elk Peak on August 11, 2016, by the U. S. Board of Geographic Names to honor medicine man Black Elk of the Oglala Lakota (Sioux). The two names are synonymously used in this article as the same peak.

The first attempt to accurately measure the elevation of Black Elk Peak was in 1874 during the Custer Expedition. Among those on the expedition was William Ludlow, the chief engineer who oversaw mapping and data collection for the 7th Cavalry. Ludlow used a barometer and arrived at an elevation of 9700'. One year later, during the Newton-Jenney Expedition of 1875, Horace P. Tuttle used a Green's mercury barometer, one of the best instruments of the time to determine elevations on high peaks. Tuttle coordinated his measurements with simultaneous readings at the Union Pacific Railroad depot in Cheyenne, Wyo. The difference between the two barometer readings, when added to the known sea level elevation at Cheyenne, resulted in elevations of 7369.4' and 7368.4', varying greatly from the 9700' elevation previously obtained by Ludlow.

The elevation results of the Newton-Jenney Expedition were not published until 1880 due to the extent of information gathered. Three years previously, in 1877, the U. S. Geological Survey of the Territories had published Ludlow's elevation of 9700' in their Lists of Elevations fourth edition since Tuttle's updated information was not yet available. Bulletin No. 5 of the U. S. Geological Survey (USGS) in 1884 continued to use Ludlow's elevation, but in 1891 USGS made the change in Bulletin No. 72 in favor of Tuttle's elevation of 7368'.

In 1893, members of the USGS triangulation crew ascended to the top Black Elk Peak to place an iron bolt in the granite rock for a monument. The initial triangulation network in the Black Hills tied together many of the most prominent peaks and formed the basis for surveying the original 30-minute topographic sheets in the area. The vertical datum used by USGS during their earliest mapping in the Black Hills is unknown, but the first quad sheet for the Black Elk Peak area, published in 1896 and designated "Harney Peak", shows an elevation of 7215' at the peak. Bulletin No. 72, however, lists the elevation as 7368' for Black Elk Peak (Harney Peak) and an elevation of 7215' for Terry Peak. Was this an error where the elevation for Terry Peak was mistakenly shown on the quad sheet as the elevation of Harney Peak? If so, it was one of the more substantial blunders ever made by USGS.

The Deadwood Datum, established by USGS in the Black Hills in 1896, became the first published vertical datum in the region. This datum was based upon an elevation supplied by the FE&MV Railroad at Deadwood. (See The American Surveyor Vol. 9, Issue 7). One year later, in the Black Hills in 1897, a second triangulation survey by USGS added more points to the network and tied into the monument on Black Elk Peak. It is believed that elevations were carried with the triangulation during this survey and that the elevations of the peaks were determined by triangulation. USGS, however, never published data to explain how the elevations of the peaks were derived. Bear Mountain, a peak located 10 miles west of Black Elk Peak, was among the 1897 stations. It was one of two peaks that were close to a level run where elevations could be brought to the triangulation stations without much difficulty. During the 1897 occupation of the monument on Bear Mountain, angles were turned to the station on Black Elk Peak giving strong evidence that this was when the elevation of 7240' was determined. The 7240' elevation appeared on the quad sheet of 1901.

When the first fire lookout tower was placed on Black Elk Peak in 1911, a portion of the peak was removed to provide a level surface for the structure. This action also removed the 1893 triangulation station which was assumed to be the reference point for the 7240' elevation. A second tower was constructed in 1919 and the current structure was completed in 1939.

In 1908, the U. S. Coast & Geodetic Survey (USC&GS) arrived in the southern portion of the Black Hills and tied their leveling into the Deadwood Datum. USGS then adjusted their Black Hills bench marks, numbering over 500 permanent monuments, to agree with those of USC&GS. The elevations of the peaks on the USGS quad sheets were changed to reflect an increase of 2 feet. This adjustment established the elevation of Black Elk Peak at 7242' where it remained unchanged for over a century.

In December of 2015, South Dakota historian and author Paul Horsted contacted me to inquire where the elevation on Black Elk Peak was referenced. Paul had authored an article about a nearby peak 100 yards south of the Harney Peak lookout tower which was thought to be higher. During the 1875 Newton-Jenney Expedition, a topographer with the group, Valentine T. McGillicuddy, ascended to the top of this other peak on July 23, 1875. After assisting others to the top, the men set up their instrument, scanned the area, and concluded that they were on the highest peak. A photo was taken which confirms they were on the peak south of where the lookout tower is located.

Most published sources list the elevation of Black Elk Peak at between 7240'-7244', but none have ever stated a defined location on the peak. A spokesperson contacted at one government agency in the Black Hills erroneously stated the elevation was referenced to the tip of the lookout tower's lightning rod. In 1950, USC&GS established a bronze disk triangulation station, HARNEY (PID OT0810), approximately 350' west of the lookout tower on a lower and more accessible area of the peak. This location is approximately 18' lower than the rock surface by the lookout tower, yet the NGS datasheet for this monument listed the elevation for the monument as 7244'. Since the elevation long associated with the peak predated both the first lookout tower and the USC&GS monument, something was amiss. Also, since part of the peak had been removed for the first tower, the elevation could not have remained the same. It was then decided to conduct an independent and accurate survey.

On the morning of September 15, 2016, just one month after Harney Peak had been assigned its new name, Black Elk Peak, Horsted and Penry packed surveying equipment for the three mile hike to the top. The triangulation station monument was used as a basis for beginning the differential levels. To begin the survey, an assumed elevation of 100.00 feet was assigned to the monument. Closed loop levels were run to establish elevations on two geodetic reference marks, a drill hole where an old airway beacon tower had once been located and the concrete floor of the lookout tower. A bolt embedded in the granite near the northwest corner of the lookout tower served as an auxiliary bench mark near the tower. To establish the elevation of the peak south of the lookout tower, which we named "McGillicuddy Peak", the level was set up near the lookout tower and adjusted until the horizontal crosshair matched the highest point of the peak. A reading was then taken on the bolt which gave us the difference in elevation between the bolt and the top of the other peak. While the levels were run, a Sokkia GSR2700ISX receiver collected data on the triangulation station.

The following day, a second hike was made to the peak. Accompanying and assisting with more equipment was fellow surveyor Kurt Luebke, from Missoula, Montana, Paul's wife Camille and daughter Anna Marie, Jerry's wife Jenny, and experienced rock climber Daryl Stisser. Earlier that morning, Jerry and Kurt placed Trimble 5800 receivers on USC&GS bench mark "A 178" north of Hill City and a new bench mark, "Bench Mark No. 1", from which an elevation had been transferred from "C 178" south of Hill City. Both USC&GS bench marks had been placed in 1934 and had adjusted published elevations of the NAVD 1988. A third receiver, a Trimble R8 Model 3, was placed on station HARNEY.

After Paul and Daryl scaled to the top of McGillicuddy Peak with a mini prism, Jerry took vertical angle measurements with a total station set up on the airway beacon drill hole west of the lookout tower. To determine the height of the lookout tower roof and the tip of the lightning rod, measurements were taken to Jenny holding a prism inside the tower on the floor by direct line of sight through the west window. Kurt checked all obtainable points with a Trimble RTK rover including the highest natural rock near the lookout tower.

After the data was processed, the elevation for triangulation station HARNEY was determined to be 7213.21 feet NAVD88. The basis for this elevation was our Bench Mark No. 1, the best realization of NAVD88. The accuracy of the ellipsoid height was determined to be 0.02 to 0.03 meters (0.07 to 0.10 feet). From the National Geodetic Survey Toolkit, the estimated accuracy of the geoid height at station HARNEY is 0.047 meters (0.154 feet). Add these two factors together, 0.047 meters + 0.025 meters = 0.072 meters (0.236 feet) which is virtually identical to the elevation difference of 0.067 meters (0.220 feet) that was observed by comparing the Continuously Operating Reference Station (CORS) derived elevation obtained through Online Positional User Service (OPUS) which processed the GNSS data from Bench Mark No. 1.

The difference in elevation of the various points obtained by differential leveling on the first day, and by using GPS RTK on the following day as a secondary check, did not vary by more than 0.01 feet between any two points. The only exception is the highest natural rock on the north side of the lookout tower where measurements varied by 0.04 feet.

The elevation for the top of the lookout tower roof and the tip of the lightning rod were determined by adding the difference in elevations from the elevation of the airway beacon drill hole to what was determined by vertical angle with the total station from the drill hole. The elevation determined for the highest natural rock on McGillicuddy Peak was determined by adding the difference in elevation from the bolt near the lookout tower as determined by differential levels. This checked within 0.01 feet when compared to the elevation determined by vertical angle from the airway beacon drill hole.

The highest natural rock on Black Elk Peak by our survey is 7231.32' and the highest natural rock on McGillicuddy Peak is 7229.41'. This places Black Elk Peak just 1.91 feet higher. However, a comparison of the 1875 photo to a modern photo shows that portions of the south peak have been removed. The top of the lookout tower roof is 7257.20' and the tip of the lightning rod is 7262.30'. All elevations are referenced to NAVD88.

The results of our survey were published in the December 26, 2016, issue of the Rapid City Journal and subsequently republished in several other major newspapers across the country. Despite our corrected elevation determination, it is unlikely that any government agency will change their long standing elevation of 7242'. When the planned National Spatial Reference System is implemented in 2022, the elevation at Black Elk Peak is projected to be approximately 2.4' lower which will then make it closer to 7229'.

More information about Harney Peak can be found at http://www.penryfamily.com/harneypeak/main.html

Jerry Penry is a licensed land surveyor in Nebraska and South Dakota. He is a frequent contributor to the magazine.

A 5.000Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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