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geodetic surveying 1940-1990

1807 - 1940

Joseph F. Dracup
Coast and Geodetic Survey (Retired)
12934 Desert Glen Drive
Sun City West, AZ 85375-4825

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From Tables to Mechanical Calculators

At the beginning of the American geodetic experience, no mechanical calculators were available and the computations were made using a variety of tables including logarithms, augmented by the individual computer's arithmetic abilities. Despite of what today would be considered the most extreme of primitive computational means, the work got done.

The method of least squares was introduced in 1847 or 1848 and as early as 1868, adjustments were carried out involving closures in length, azimuth, latitude and longitude, a formidable task even in later years.

Accuracy estimates determined directly from least-squares adjustments were not routinely computed until the mid 1960's because of the additional effort involved and other approaches were taken to come up with acceptable substitutes. Charles A. Schott in the Superintendents's Report for 1865, p. 192, explains the problem and the rationale for its solution as follows: The strict application of the method of least-squares in connection with the computation of probable errors of the adjusted parts of a triangulation becomes, in our case, impractical from its laborious nature, and a shorter method must be sought and followed, which, while it is a sufficient approximation of the truth, yet furnishes us with all desirable data to judge the accuracy of our results. The approximations took several forms depending on the element (length, azimuth or position) for which the accuracy estimate was desired. Most evolved from the specific condition equation for the element and all included the probable error of the angle (or direction) derived from the adjustment. That for the length eventually became the strength of figure formula, long used to evaluate the strength of triangulation and in determining the need for additional base lines.

Doolittle Makes It Less Work

In 1878, Myrick H. Doolittle made a combination of improvements to Gauss' method for solving normal equations that continued in general use for more than 80 years. European geodetic circles insisted on dubbing the method as Gauss-Doolittle and so it remains today. However, in 1924 when F. R. Cholesky, a European (France), modified Doolittle's procedure, this method is identified as Cholesky or Cholesky-Rubin. T. Rubin, another European (Sweden), apparently discovered the same approach as Cholesky, but two years later.

Crude and cumbersome mechanical calculators appeared later in the 19th century and despite their awkwardness reduced the task of making multiplications and divisions, the major chore in computations. Later improvements, including small electric motors resulted in further reductions to the computational effort and made feasible the simultaneous solution of several hundred normal equations.

Azimuths From the South - Why ?

From 1850 to the adoption of NAD83 in 1986, azimuths in geodetic surveys were reckoned from the south, clockwise, rather than from the more logical origin, north, used by land surveyors. Walter D. Lambert in a short 1946 article and some notes compiled in 1954 gave several explanations, any of which could suffice as a good reason for the practice.

In his 1954 notes he reports that in Hassler's 1817 work and after 1832, there was no uniformity, sometimes azimuths were reckoned from the north and on other occasions from the south, and furthermore in either direction, without any specific notation whether east or west. The remainder of the notes conclude from various writings of French geodesists of the 1800-40 period that they preferred to measure azimuths from the south around to west and according to him so did their American colleagues.

His 1946 article provides probably the best rationale for the practice. Lambert noted that Charles A. Schott was a German trained geodesist and while not a student of Karl Friedrich Gauss (1777-1855) he was well aware that Gauss followed the general practice of azimuths from the south, clockwise, in his Hanoverian triangulation. And, further, that Schott joined the Computing Division shortly before 1850, was highly regarded from the beginning and it was very likely he was responsible for the bureau adopting the practice. After 1986, azimuths are measured clockwise from north.

U.S. Horizontal Datums

In 1879 the first national datum was established and identified as the New England datum. Station PRINCIPIO in Maryland, about midway between Maine and Georgia, the extent of the contiguous triangulation was selected as the initial point with its position and azimuth to TURKEY POINT determined from all available astronomic data, i.e. 56 determinations of latitude, 7 of longitude and 72 for azimuth.

Later its position was transferred to station MEADES RANCH in Kansas and the azimuth to WALDO by computation through the triangulation. The Clarke spheroid of 1866 was selected as the computational surface for the datum in 1880, replacing the Bessel spheroid of 1841 used after 1843. Prior to 1843, there is some evidence that the Walbeck 1819 spheroid was employed.

The datum was renamed the U.S. Standard datum in 1901 and in 1913 the North American datum (NAD) as Canada and Mexico adopted the system. In 1927 an adjustment of the first-order triangulation of the U.S., Canada and Mexico began and was completed about 1931. The end result was the North American datum of 1927 (NAD27).

It was not a simultaneous solution because it was simply economically impractical to do so with the available computing equipment. Nonetheless, it was the largest geodetic computation effort to that time. More importantly, the resulting datum was the first to be oriented by Laplace azimuths strategically spaced throughout the triangulation. The azimuth to WALDO in the datum definition was changed by about 5" due to the inclusion of a Laplace azimuth at the nearby SALINA base line. Its inclusion in the NAD27 definition was only for completeness purposes since the datum is actually oriented by 175 Laplace azimuths held fixed in the adjustment as noted previously.

Hayford Ellipsoid

In 1909, John F. Hayford using data only from the U.S. triangulation determined new dimensions for the figure of the earth, appropriately named the Hayford spheroid. The International Geodetic and Geophysical Union adopted the parameters in 1924 as the basis for the International Ellipsoid of Reference and it is presently used in several countries.

Earlier he had perfected the strength of figure formula used in deciding where base lines are required in the triangulation. The original concept was developed and used in the U.S. Lake Survey and later improved by William H. Burger (C&GS). Hayford also was the co-author with Thomas W. Wright, formerly of the Lake Survey, of the widely used text Adjustment of Observations. He served with the C&GS for 20 years and was Chief of the Computing Division and Inspector of Geodetic Work for about 10 years.

First National Accuracy Standards

In 1921 a committee decided that the C&GS nomenclature for accuracies of geodetic surveys of Primary, Secondary and Tertiary would henceforth be identified as Precise, Primary and Secondary. Looking back over more than 70 years it appears now to have been a political decision, probably some agency objecting to the tertiary classification for their work. As usual with such edicts, it created nothing but confusion.

Accordingly in 1925, the Federal Board of Surveys and Maps adopted the now familiar standards of Firstorder, Second-order and Third-order accompanied by the also familiar 1:25,000, 1:10,000 and 1:5,000 length and position closures, that were reaffirmed in 1933 and remained in place until 1957.

Traverse Replaces Triangulation 1917-1927

By 1900 the C&GS had observed about 5,150 miles of first-order triangulation and the USLS about 1,650 miles. Between 1900 and 1925 about 13,000 miles of the same class triangulation was measured in the western half of the country including the 1,460 mile 49th Parallel arc straddling the U.S.-Canada border from the Lake of the Woods, MN and the Pacific Ocean observed jointly with the Geodetic Survey of Canada (GSofC).

Due to the high cost of building wooden towers, little or no triangulation was observed from 1900-27 in the eastern part of the country. First-order traverse was substituted because routes could be selected along railroads, with the measurements facilitated by utilizing the rails to support the tapes throughout and then projecting the distances to the stations offset from the tracks. Between 1917 and 1927 some 3,300 miles of traverse were observed in 13 states, all east of the 98th Meridian arc except for about 100 miles in South Dakota.

After the development of the Bilby tower in 1926, survey methods for the eastern half of the country reverted to triangulation and between 1927 and 1931 about 9,000 miles of first-order work was accomplished. Among the major pieces of work completed after 1900 were the 98th Meridian arc, 1,720 miles in length observed 1897-1907; 49th Parallel arc, mentioned previously, about 1,460 miles long measured in 1924 and the last of the great triangulations, the Atlantic coast arc, perhaps 1,600 miles in length from Providence, RI to Key West, FL completed in 1932.

NAD 27

In the adjustment that created NAD27, all the first-order triangulation and about 100 miles of first-order traverse for a total of 15,050 miles were included in the western half computation. For the eastern half adjustment only the triangulation west of the Eastern Oblique arc amounting to 11,850 miles was used including USLS (1,650 miles) and GSofC (630miles) work, but none of the first-order traverses. Other omissions were: International Boundary Commission (IBC)-GSofC triangulation observed before 1920 from Lake Superior westward to Namakan Lake (about 200 miles) because the connection to the 98th Meridian arc was a first-order traverse measured on the frozen Rainy River in Minnesota and a 200 mile section of the Mississippi River arc from St. Louis northward completed in 1931, possibly because the records were not yet received. The work to the east of the Eastern Oblique arc, including the entire Atlantic coast arc and other triangulation in parts of Virginia, North and South Carolina, Georgia and Florida was left out because traverses were involved.

By 1950 it was evident that NAD27 had many problems caused by large loops in the west and an insufficient number of base lines and Laplace azimuths. Estimates made then suggested that half again as much of the 26,900 miles of triangulation included in the computation and twice as many base lines (112 included) and Laplace azimuths (175 included) would be needed.

By 1940, this amount of new work was largely available, made possible by civil works' funds allotted to aid the unemployed, but no one in 1927 foresaw this happening. Hindsight, of course is always better than foresight.

Reconnaissance Surveys

Reconnaissance surveys, the in-field planning and selection of locations for triangulation stations were always part of geodetic operations in the U.S. However, it didn't become a separate and distinct function until the 1880's when multiple observing parties began to come on the scene. Up to then, there was only an occasional need to plan more than a few figures ahead and this could easily be done by the units as work progressed.

The strength of triangulation depends solely on well-shaped triangles and sufficient redundant observations to verify the acceptability of the angle measurements. The latter was the basis for adopting the specification, during Bache's time, that all triangulation was to consist of braced-quadrilaterals and/or central point configurations.

How High is Enough ?

Fulfilling these basic criteria often required towers for intervisibility and deciding on their heights was a problem within itself. Prior to Bilby towers, the cost and time needed to erect wooden signals was a major factor for making an additional effort to assure that a minimum height would suffice. Profiling lines by various means, including the determination of elevations from vertical angles and estimated distances, and by barometric observations were common solutions to the problem at all times. The effect of the earth's curvature and refraction often had to be worked into the equation, as well. For examples: On a 10 mile line, absolute flat terrain, 15 ft. towers at each end, or 58 ft. at one end, would be required for minimum clearance; and for a 20 mile line, same situation, 58 ft. at each end, or 230 ft. at one end.

There were two schools of thought, however, on how extensive the profiling effort should take. One side contended that regardless of the effort, blocked lines would happen, and the usual solutions, raising the heights of towers or adding another station would be less costly overall. Others thought otherwise. And many who traveled some distance to reach the station site, only to find a line not visible, would agree with the latter.

The Job Entailed

Selecting base line sites and planning the base expansion net to the triangulation was another responsibility. Depending on the length of the base that could be accommodated by the location, the connecting figure had to be very carefully chosen, so as to minimize the number of observed angles involved in the expansion of the distance, and that they would be the strongest possible. Prior to the availability of EDMI, the ratio of triangulation lines and bases was about 3:1 on the average, albeit some approached 10:1.

Traverse, unlike triangulation and trilateration, has no strength of figure per se, and the general instructions were to select points about equally spaced and in a straight a line as possible. More frequent astronomic azimuths and positions, than required for triangulation, were observed to help control sway in the survey.

In addition to selecting the station sites, lines to be observed and height of towers required, the reconnaissance engineer was responsible for preparing a sketch showing that information, ties to established control and marks of other agencies, and topographic features such as landmarks that might serve as intersection stations. Also, prepare descriptions on how to reach the proposed station sites, recovery notes for old stations,indicate types of marks to be set at each station, setup contacts with public officials and property owners and specify any arrangements made with the owners in regard to crop damage, etc.

Party Makeup and Can Do Spirit

Reconnaissance parties generally consisted of a Chief of Party (Assistant prior to about 1910), one or two assistants, and the necessary vehicles and equipment, usually an absolute minimum. As a case in point. In 1911, Jasper Bilby and one assistant ran the reconnaissance for the 104th Meridian arc from Colorado Springs, CO, to the Canadian border, about 720 miles, in a little over 3 months, selecting sites for 74 primary stations, 23 supplementals and 2 base lines. His equipment was 3 mules, 1 wagon, 1 riding saddle, necessary tools for repairing the outfit, 1 tent, cots and bedding for 2 persons, and a few cooking utensils. He also had a 4-inch surveyor's transit, a prismatic azimuth compass, a field telescope, binoculars, a set of drawing instruments and all available maps.

In later years, trucks were substituted for the mules and wagon, and living conditions were different and usually better, but all else, including the work itself, remained substantially the same. GPS changed all this and reconnaissance surveys are considerably simpler today, no intervisibilities required for example, yet geometry and other factors are no less important than previously.

No formal reconnaissance was usually made in leveling. Bench mark setters selected the locations and set the marks, at intervals as called for by the project instructions, sometime prior to the observations.

NOTE: (C&GS) following names, for events after 1920, indicates they were commission corps officers at the time.

Alaska - Hawaii - Philippines

By 1940 first-order triangulation on NAD27 had been extended to Skagway in southeast Alaska and earlier in the century first-order surveys from Shelikof Strait to Cook Inlet to Anchorage and on to Fairbanks were completed on an independent datum. Lower-order surveys computed on several independent datums covered much of the coastal areas including the Aleutians. In 1943 Skagway and Fairbanks were connected by first-order triangulation bringing NAD27 to the main land mass, albeit it would be more than a decade before all of Alaska was on a single datum.

Between 1900-40 geodetic surveys, mostly second-order triangulation, were established in the Philippines, Hawaiian Islands, Puerto Rico-Virgin Islands and the Panama Canal Zone with positions based on datums specifically developed for each region. Surveys of the islands west of Hawaiian chain, including Midway were based on local astronomic datums. Surveys on Midway Island were completed late in November, 1941 and personnel were en route by C&GS ship to Pearl Harbor on December 7, 1941. Their arrival was delayed due to running zigzag courses under radio silence causing a fear for several days that they had been lost in the first actions of the war.

Most of the work in Puerto Rico and the Hawaiian Islands was upgraded in the 1960-80 period. During the same time frame, new surveys were carried out on Guam, American Samoa and for the Defense Department, on Kwajalein in the Marshalls.

The Philippines presented a unique situation because of the agreement that 50 years after the war ended in 1898, the islands were to become an independent nation. The role of the C&GS was therefore an advisory one to the Insular Government and to this end about 1906 a processing office, including computations and map making functions was set up in Manila. All the geodetic records were held there and only the lists of adjusted geographic positions were furnished the Washington office.

Much of the geodetic work, primarily second-order triangulation, as noted earlier, including the connection to the British surveys on Borneo, was completed when the war began in 1941. An extremely difficult task to accomplish because of the tropical jungle, mountainous terrain and occasionally hostile natives.

The processing office was taken over by the Japanese early in 1942 and destroyed in 1944 during the retaking of the islands, with a loss of most of the geodetic records. George D. Cowie (C&GS), in charge of the office was killed in the bombing of the city on Christmas Eve, 1941, and several C&GS employees and a few families were imprisoned by the Japanese for the duration. One prisoner, Joseph W. Stirni (C&GS) was killed in 1945 when a ship taking him to Japan was torpedoed. Two others, Clarence F. Maynard, a civilian mathematician and George E. Morris (C&GS) were captured on Bataan, survived the Bataan Death March and imprisonment in Korea. Maynard returned to the Philippines after the war, remaining until all C&GS personnel were recalled in 1950. On his return, he was Chief, NY Computing Office for several years.

Earthquake Investigations

Following the 1906 San Francisco earthquake, a selected scheme of triangulation from Monterey to Fort Ross involving primary, secondary and tertiary stations and a detached net of tertiary points at Point Arena were reobserved to determine the amount of crustal motion. This was the first time in the U.S. that triangulation was reobserved for this purpose. Displacements were computed for all points in the disturbed area resulting from the 1906 event and where possible for stations effected by an earthquake in 1868 also.

Between 1922-24, the primary triangulation from Lake Tahoe to San Francisco to Santa Barbara and eastward to southern California was reobserved for the same purpose. Extensions were reobserved in 1924-25 northward to Point Arena, east to Carson Sink, NV and to western Arizona as further verification of stability of the terminal points.

One special point of interest arose from a discussion of the computations. Arthur L. Day, Director of the Carnegie Institution's Geophysical Laboratory wrote to Bowie and Walter F. Reynolds, Chief Section of Triangulation, in 1931 supporting a suggestion made by a reviewer of the results, Harry O. Wood in 1930 that circular errors, representing the precision of the observations be determined in the adjustment and shown on the sketches with the movement vectors. The request has to be among the first anywhere for such information. Both nicely sidestepped the issue knowing full well determining such estimates was impractical at the time, especially so because the C&GS used the method of condition equations for their adjustments and that method was the least amenable to providing such data. In fact no method could readily do the job then. It wasn't until about 40 years later that circular errors and error ellipses were routinely computed.

Other crustal movement resurveys included the 1929 Newport Beach to Riverside arc, CA following the Long Beach 1933 earthquake with little movement indicated. Also, during the 1930's several lines were releveled in San Francisco, San Jose, Los Angeles and vicinity, San Diego area and the Imperial Valley, CA, with all showing some displacements. One or two arcs and a number of level lines in California and other parts of the country were observed specifically for future crustal motion studies.

Speed of Light

In 1922-23, the most accurate invar taped base line ever, with a precision of 0.2ppm one sigma, was measured near Pasadena, CA. The sole purpose for the 20.9 mile base line was to provide Albert A. Michelson with the best possible distance between points on Mount Wilson and San Antonio Peak used in his experiments to determine the speed of light.

To assure the least loss of accuracy in projecting the measured distance to the line between the two points, the base was measured parallel to that line and to its approximate length. Astronomic positions were determined to correct the angles for the deflection of the vertical. The work was carried out under the direction of Clement L. Garner (C&GS), later to succeed William Bowie as Chief, Geodesy Division.

Bowie and the C&GS were interested in Michelson's experiments in the hope that means could be found to measure distances using light. It was not to be. The experiments were not totally successful and the Great Depression began, leaving Erik Bergstrand to develop the equipment 25 years later, in Sweden.

The 1938 AMSTERDAM Avenue base line in New York City presented a similar problem, but here the stations were atop high buildings. It was necessary first to project the base vertically to temporary points offset from the stations and then a lateral shift to the station marks.

Early Urban Surveys

Between 1903-08 a first-order triangulation network encompassing greater New York City was observed; Cincinnati did the same on their own in 1912-13 with Hugh C. Mitchell, on assignment from the C&GS in charge and in the mid 1920's, combined first-order triangulation and traverse systems were established for Rochester, NY and Atlanta, GA. These were the forerunners of the numerous State-wide, county and urban nets observed later in the century. Prior to 1940, several cities developed networks on their own or with private sector assistance. As a case in point, first-order control surveys and associated topographic mapping for a number of municipalities were accomplished by the R.H.Randall Co. of Toledo, OH between 1920-34.

Tangent plane coordinate systems, most at ground level, were setup for these early urban surveys. After the advent of the State coordinate system,only the Cleveland Regional Geodetic Survey (CRGS) adopted a tangent plane ground level grid.

SPCS - UTM and Oscar S. Adams

In 1933-34, Oscar S. Adams ably assisted by Charles N. Claire developed the State Plane Coordinate System (SPCS) at the request of George F. Syme a North Carolina Highway engineer. Syme died shortly after the North Carolina system was developed being succeeded by O.B. Bestor to carry on the cause. Bestor was in charge of the State local control project established in 1933, later identified as the North Carolina Geodetic Survey. Most State and the few county projects involved in this program also were so named. Colonel C. H. Birdseye of the USGS, with a strong interest in Statewide coordinate grids also participated in the several conferences leading to the decision to honor Syme's request.

The first tables for computing Lambert coordinates were developed for North Carolina and the first tables for the transverse Mercator grid were for New Jersey. Tables were prepared for all States early in 1934. For the first time all horizontal control stations previously defined only by latitudes and longitudes would be available in easy to use plane coordinates.

Adams had many notable accomplishments prior to this work. For example, he authored or co-authored 22 Special Publications and Serials dealing mostly with map projections and adjustments. This group includes Application of the Theory of Least Squares to the Adjustment of Triangulation issued first in 1915 which provides the mathematical basis for adjustments by condition equations and observation equations on the ellipsoid and still remains a viable part of the literature.

He was actually the father of NAD27 since he gave Bowie's adjustment proposal life and personally made many of the computations. Later he was directly involved with the creation of the Universal Transverse Mercator (UTM) system used by the U.S. Army worldwide, although his association with the project is not well known. Adams also collaborated with Bowie in 1918 in developing the Military Grid System, the forerunner of UTM, dividing the country into seven zones, 9 of longitude wide, with the polyconic projection the basis for the grid.

Great Depression Surveys

The 1930's saw a huge increase in funds for public works as part of the effort to get the country out of the Great Depression and the C&GS field and office staffs were significantly increased. At the height of the program more than 1,000 employees were in the field and as many as 12 observing units, from a single party were working some nights.

For the first time ever a number of second-order arcs were observed by geodetic parties, bringing grumbles from purists and rightfully so, the savings in time and effort were very small. In addition about 23 States and a few counties setup geodetic surveys, under the overall supervision of the C&GS, with the intent to establish second-order horizontal and vertical control at the local level.

In the earliest stages all States participated and more than 10,000 unemployed surveyors, engineers and technicians were given meaningful jobs, albeit the pay was less than $20 a week. Most of the 23 geodetic surveys accomplished some work although only a few made substantial contributions. Among those that did were: Alabama, Florida, Georgia, Louisiana, Massachusetts, New Jersey, North Carolina, Oklahoma, South Carolina and Tennessee; among the counties: Monroe and Westchester in New York and the regional geodetic survey in Cleveland, OH. Except for Massachusetts and Westchester county, where first-order triangulation also was observed, all surveys involved traverses.

Whether the expenditure of the funds had the desired overall economic effect is still being debated, however there is no doubt the funds spent were highly beneficial to the geodetic control program as many thousands of new stations and bench marks were established. To wit, there were more than 100,000 points of all orders of accuracy in the horizontal net by 1940.

Geodetic Leveling, Datums, and Instruments

Geodetic leveling has always played second fiddle to horizontal surveys. Perhaps this is so because leveling is perceived as a simple procedure, although it most certainly is not. Some form of leveling, mostly trigonometric in nature was always observed in order to provide elevations needed to reduce base lines and angle observations to sea level. As a matter of fact, the observations were often carried out as a separate event using specially constructed vertical circle only instruments.

As work on the Transcontinental arc progressed westward it was recognized that vertical angle elevations would not be of sufficient accuracy for the purpose. Accordingly a line of precise levels following the route of the triangulation was begun in 1878 at the Chesapeake Bay and reached San Francisco in 1907.

In 1898, an adjustment was made of the first 25 circuits and a second in 1903 to include the large amount of new data observed in the interim. Partial adjustments were carried out in 1907 and 1912 to include the ever increasing work. In 1929 a general adjustment was made which included 45,000 miles of U.S. first-order leveling and 20,000 miles of similar accuracy Canadian surveys, with sea level planes at 26 tidal stations held fixed. The Canadians had recently published the results of their observations and didn't accept the combined adjustment values. Difference of elevations at common bench marks didn't exceed 0.5 ft. The U.S. data also includes precise leveling observed by the Corps of Engineers, U.S. Geological Survey and other organizations.

By 1940, about 260,000 miles of first- and second-order leveling had been observed. The elevation datum was known as the Sea Level Datum of 1929 (SLD29) until 1973 when the name was changed to the National Geodetic Vertical Datum of 1929 (NGVD29).

Prior to 1899, geodetic leveling in the U.S. was observed using wye levels and target rods. Long telescopes were common to such instruments and critics claimed Americans bought their levels by the yard. In 1899, the Fischer level designed by Ernst G. Fischer of the instrument division, a dumpy type and speaking rods replaced the earlier equipment and were used for almost 70 years with only slight modifications. Invar strips were added to the rods in 1916.

Mt. Whitney - Precisely How High ?

Elevations of high mountains are rarely determined by spirit leveling, most being the result of trigonometric methods, a k a zenith distance/vertical angle elevations. As a matter of fact, the highest mountains are seldom occupied for horizontal positioning either for obvious reasons, clouds and weather conditions among them. Despite these negative possibilities, in August 1925, Lansing G. Simmons (C&GS) was sent to Lone Pine, CA to observe first-order leveling from bench marks on the Owens Valley line to the summit of Mount Whitney, the highest peak in the then 48 states. The purpose was for crustal motion studies where future relevelings would give indications whether the mountain was growing or not. Since it was late in the season, Simmons decided to level from the summit down, but found the summit trail from Whitney Portal, about 14 miles west of Lone Pine, blocked by rock sides and learned furthermore that no horses had been over the route in several years. He then decided to horsepack the outfit to Army Pass at an elevation of 11,000 ft. about 10 miles south of Mount Whitney, from where the party would backpack the equipment to a base camp at 14,000 ft., about one mile south of the summit.

Despite some of the 8 man party suffering from the altitude, that was further compounded by living in pup tents, with the only water from melting snow and the only fire from a gasoline stove, they were able to complete the leveling from the summit, marked by a USGS disk set in 1901, to a permanent bench mark near the base camp in a week's time, a vertical distance of about 500 ft. Bad weather set in with snow, hail, cold and high winds and there being little chance with September approaching for better conditions, the camp was backpacked to Lone Pine Lake near Whitney Portal at an elevation of about 8,400 ft. where the leveling was picked up again for the 13-14 miles into Lone Pine.

Two years went by without the Forest Service or local people clearing the trail to Mount Whitney so in June 1928, John H. Brittain (C&GS) was ordered to Lone Pine to form a party, complete the first-order leveling from Whitney Portal to the summit and with authorization to open the trail. He made his first camp at the 10,400 foot level, opened the trail to 11,500 ft. taking only one day to do the job and completed the leveling to that point. From a second base camp at 12,000 ft., leveling was run to the summit marked by the USGS tablet described earlier by Simmons. This was a remarkable piece of work. To carry the elevations over a vertical distance of 6,126 ft. and extremely rough terrain in 18 days of leveling required determination and esprit de corps that would rarely be found today.

No resurvey has been made to date. Simmons and Brittain went on to long and distinguished careers in the C&GS. Simmons was the Chief Geodesist for about 20 years, retiring in 1967 and Brittain at the time of his retirement in 1961 was Chief, Geodesy Division. Lansing G. Simmons died in 1986, at age 84.

The experience here seems to have discouraged further attempts to level to the summits of high peaks even when roads are available such as to Pikes Peak and Mount Evans in Colorado, both over 14,000 ft. However, with increasing interest in replacing conventional leveling with GPS observations, the tests presently underway (1994) might consider including first-order leveling to these and other readily accessible peaks as part of the examinations.

As geodetic surveying in the U.S. entered the fifth decade of the 20th century, the first-order triangulation and leveling were basically complete. Future priorities would be to fill in the gaps, strengthen and update the networks and carry out new adjustments of NAD and SLD (NGVD). All would come to pass and much more in the next 50 years.

This brief and informal history of U.S. geodetic surveys covers the more significant happenings plus a few of the more interesting incidents in the period 1807-1940. The decades to follow would be a most dynamic and amazing era as the surveying world would ever see with new instrumentation, methodology and computers eventually dominating the scene.



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