Coast and Geodetic Survey (Retired)
12934 Desert Glen Drive
Sun City West, AZ 85375-4825
Series of Name Changes
began using the title Superintendent of the Coast Survey in
his 1836 report to the Secretary of the Treasury, the year the
bureau was transferred to that department. This usage continued
until 1865 where that and subsequent reports to 1877 showed
United States Coast Survey. In 1878 Congress changed the name
to U.S. Coast and Geodetic Survey (C&GS); in 1899 the U.S.
was dropped. In the 1970's, the C&GS became the National
Ocean Survey (NOS), later renamed the National Ocean Service
(NOS) with the geodetic functions assigned to the National Geodetic
Survey (NGS), presently an office in NOS.
End of the Beginning
continued observing the triangulation southward and after about
10 years only had reached southern New Jersey involving but
24 stations. Upon completing the observations at station BURDEN
he traveled to a station site in Delaware where during a severe
storm he fell trying to protect his instruments and was badly
injured. He returned to his home in Philadelphia where he died
on November 20, 1843.
we reach the end of the beginning. The groundwork for laying
the foundation was done. By the turn of the century triangulation
would span the nation north to south from Maine to Louisiana,
east to west from New Jersey to California, over the Great Lakes
and with work underway through the middle of the country between
the Rio Grande and Canada.
THE FOUNDATIONS OF THE NETWORKS 1843-1900
1807-43 era in American geodesy was totally dominated by one
person, Ferdinand R. Hassler. He was head and shoulders above
all others. This was not the case for the 1843-1900 years, albeit
several strong willed, very competent personalities prevailed
for long stretches, some for almost the entire period, but none
over shadowed all others as completely for as long a time as
did Hassler. Among the elite group were Alexander Dallas Bache,
George Davidson and Charles A. Schott.
Dallas Bache was appointed the second superintendent of the
Coast Survey in December 1843, being eminently well qualified
for the post having a learned interest in many scientific activities.
Born in Philadelphia in 1806, the great-grandson of Benjamin
Franklin, a graduate of West Point at age 19 and served 3 years
in the Engineers. Prior to his appointment, he was professor
of natural history and chemistry at the University of Pennsylvania
and served as superintendent of schools in Philadelphia. Later
he helped form the National Academy of Sciences and was its
Act of 1843, passed by Congress in April of that year, defined
the functions and personnel responsibilities of the Coast Survey
that, except for a few modifications, remained in place for
more than a 100 years. In fact, the enabling act of 1947 did
little more than restate the bases for the bureau that were
essentially unchanged from the 1843 definitions.
proviso in the 1843 act, unfortunately, limited the bureau's
activities to the coast, and the narrowest belt of land to support
the primary triangulation. Bache accepted the restriction, and
immediately went ahead with a broad plan to divide the Atlantic
and Gulf coasts into nine sections, where the ongoing work (geodetic,
topographic and hydrographic) would be carried on simultaneously
and to uniform standards. Two sections were added when the Pacific
coast territories were annexed.
lifted the restriction in 1871, during the superintendency of
Benjamin Peirce, when it gave permission for the measurement
of the Transcontinental arc. In 1878, the name was changed to
U.S. Coast and Geodetic Survey to reflect the bureau's responsibilities
for geodetic surveys inland.
continued Hassler's practice of personal involvement in the
field work, but didn't limit his participation mostly to geodetic
surveys as did his predecessor; albeit he spent considerable
time in making astronomic observations and measuring base lines.
In regard to the latter, he designed and William Wurdemann,
then a master mechanician in the Coast Survey, constructed compensating
apparatus that was used until 1873. Seven principal base lines
were measured using the Bache-Wurdemann equipment, the last
being the ATLANTA base in Georgia. Bache personally directed
the measurements for the first three bases at DAUPHIN ISLAND,
near Mobile, AL in 1847, BODIE ISLAND, NC in 1848, EDISTO ISLAND,
SC in 1850 and the sixth at EPPING, ME in 1857. Wurdemann later
resigned from the Coast Survey and formed a very successful
business making astronomic and geodetic instruments for clients
here and abroad.
Dallas Bache died in 1867, age 61 at Newport, RI. America had
lost one of its greatest scientists, however he left a legacy
of excellence for his successors to build on and most were able
to do so.
was the last of the superintendents to participate extensively
in field operations, the position had simply become too large
and the responsibilities too great for such personal involvements.
Following Bache's death in 1867, nine civilian superintendents/directors
served until 1929 when the position was reserved for C&GS
commissioned officers. The title was changed to director in
1920. Several of the civilian superintendents were highly regarded
scientists including Benjamin Peirce (1867-74), Julius E. Hilgard
(1881-85), Thomas C. Mendenhall (1889-94) and Otto H. Tittmann
(1900-15). The last civilian, E. Lester Jones (1915-29) was
a veterinary surgeon by profession with an outstanding record
in public administration.
of Jones' first acts was to propose a commissioned officer corps
because of the difficulties in employing and retaining qualified
personnel for the field work due to the frequent moves and other
hardships. The proposal was accepted by the Congress and the
corps came into existence during World War I. There was one
complication. The formation of the corps forced the civilian
personnel to accept a lesser role. In addition to the director,
many of the top positions in both the field and office are reserved
for officers causing occasional differences and/or resentment
to arise in the civilian group towards the corps. All in all,
however the arrangement has worked fairly well, both sides usually
accepting the situation as that's the way it is.
of the Giants
was fortunate in recruiting a number of highly qualified engineers,
mathematicians and other scientific types for the Coast Survey
with the title of Assistant. In due course, many became master
jack-of-all-trades being equally at home in the several Coast
Survey activities that included in addition to geodesy, topographic
mapping, hydrography, tides and currents, magnetism and others.
Among the group was George Davidson, a native of Nottingham,
England whose exceptional talents were recognized by Bache when
he was head of the Philadelphia school system and Davidson was
the Coast Survey in 1845 at age 20 he trained in geodetic surveys
and astronomy under the foremost engineers in the bureau including
Bache and Robert H. Fauntleroy until 1850 when he was sent to
California with 3 other civilian assistants. Travel between
the Atlantic and Pacific coasts was not an easy journey in 1850.
Overland routes were very limited, especially in the mountainous
regions and west of the 98th meridian those that did exist often
ran through hostile Indian territory. Once beyond rail and river
boat services, travel was by foot or by horse or mule conveyances.
rail service wasn't available until 1869 and it was many years
before a rail network was developed. Stage coach service from
rail heads was unreliable at best and accommodations when available,
were very primitive. Davidson and his colleagues travelled by
ship to the Isthmus of Darien (now Panama), then by available
means to the Pacific side and another ship to San Francisco,
a trip that usually took several months.
was no direct mail service with Washington for many years and
the field records and computations were sent by ship as well.
Duplicate and sometimes triplicate copies were made of all records
and kept on site, even occasionally retained after their safe
arrival was acknowledged for use in the ever expanding network.
remained on the west coast for about 45 years, the Civil War
period and a few foreign assignments excepted. During his service,
the Transcontinental triangulation, a k a the 39th Parallel
arc was completed, primary surveys near Los Angeles and Santa
Barbara Channel were underway and coastal triangulation was
extended from Mexico to Canada.
is not credited with the earliest triangulation on the west
coast, that accomplishment belongs to Robert D. Cutts, one of
the assistants who came west with him in 1850, although we can
be sure that he was a major participant. This small network
covering San Francisco Bay was observed to a secondary accuracy
between 1851-54, with scale provided by preliminary base lines,
one at the Presidio measured in 1851 and the second, the PULGAS
base near Palo Alto in 1853 and oriented by astronomic azimuths.
1876, Davidson was placed in charge of the western section of
the 39th Parallel surveys and extensions to it. In the course
of that work he measured base lines at Yolo County north of
San Francisco (YOLO base 1881), LOS ANGELES base 1889, the angulation
for the base expansions and the astronomy to orient the principal
was a man of strong personal opinions and was an ardent advocate
for the Coast Survey to assume the surveying functions of the
General Land Office (GLO), the present day Bureau of Land Management.
While there was support for his proposals, it is very fortunate
for both agencies that they never materialized. The Survey had
done some section work for the GLO in the Florida Keys in the
1850's and the experience was not a happy one for either side.
is no doubt that had his plan been accepted the section corners
would have been located, at the very least, to a minimum geodetic
accuracy thus creating a cohesive network supplemental to the
national framework. However, the cost would have been enormous
and Survey field personnel would assuredly have been bogged
down executing time consuming short line surveys, often over
or later Congress would have viewed this as an endless project,
and it very well might have been just that. GLO practices were
right for the time, with means now available for a total upgrading
of the system once all the legal ramifications for such an undertaking
this cause was lost, most others were successful. His ability
to convince James Lick to finance the great astronomical observatory
atop Mt. Hamilton is a good example of his successes. George
Davidson was unquestionably the greatest field geodesist the
Survey produced in the 19th century, the giant among giants
for only men of that breed could have executed the triangulation
through the mountain west of the time. In 1895 during William
W. Duffield's superintendency (1894-97), Davidson in his 50th
year of service was summarily dismissed, as were many other
experienced employees. In his usual pragmatic fashion, Davidson
accepted a professorship at the University of California and
went on with his life doing things his way until his death in
the field of computations, Charles A. Schott stood alone during
this period, much as George Davidson did in his area of expertise.
Schott was born in Mannheim, Baden, Germany in 1826, a graduate
of the University of Karlsruhe and joined the Coast Survey in
1848. Appointed chief of the computing division in 1856, he
held the post until his resignation on December 31, 1899, after
52 years of service.
world recognized expert on the earth's magnetic field, personally
carrying out numerous field surveys in the eastern U.S. and
instrumental in establishing magnetic observatories at Madison,
WI and Los Angeles, CA. He had a life long interest in field
activities that was culminated with the development of a contact
compensating base line measuring apparatus of unique design
in 1881 that bears his name and was used in the same year to
measure the YOLO base in California.
chief of the computing division he was responsible for a myriad
of calculations and as was his way took a distinct interest
in all of them. Much of his efforts was directed to geodetic
computations, especially the adjustment of the observations
and investigations of the results. One such examination carried
out in 1878-79 relative to geodetic and astronomic data on the
Eastern Oblique arc provided information for establishing the
first national datum and conclusively showed that the Clarke
spheroid of 1866 fit the U.S. better than the Bessel spheroid
of 1841 then in use.
results were adopted, the New England datum of 1879 as it was
named is the basis for all subsequent datums until 1983. The
Clarke spheroid of 1866 still provides the best fit for the
continental U.S., albeit the Geodetic Reference System of 1980
(GRS 80) was adopted in 1983 for other reasons.
was a prodigious writer authoring more than 160 scientific articles,
papers and reports including two volumes detailing the results
of the primary triangulation that were hailed by geodetic circles
worldwide. The volumes are The Transcontinental Triangulation
and the American Arc of Parallel Sp.Pub.no.4 1900, 871pp. and
The Eastern Oblique Arc of the United States and the Osculating
Spheroid Sp.Pub.no.7 1902, 394pp. Charles A. Schott died in
1902. We will never see his kind again.
and Central Points
in Bache's tenure a decision was reached for the triangulation
that only quadrilaterals with both diagonals observed, commonly
called braced quadrilaterals or central point configurations
would be permitted. The reason for this specification is these
figures provide at least one geometric condition involving the
angles, known as side conditions or equations. These equations
utilize the sines of selected angles taken in a particular sequence
and give a better evaluation of the worth of the angles than
an examination of the triangle closures alone.
requirement was met for all the principal triangulation and
most of the secondary work except for parts of Hassler's early
net and pieces of the U.S. Lake Survey triangulation observed
later in the century.
first of several significant advances in American geodetic surveying
that were to be made in the next 100 years was the development
by Sears C. Walker in 1847 of a method for determining time
differences between places using the electric telegraph, invented
only a year earlier. As a result more accurate astronomic longitudes
were determined leading to subsequent improvements in Laplace
corrections to astronomic azimuths.
the transatlantic cables were in place later in the century
the same principle was employed to determine a more accurate
cardinal longitude for North America, relative to Greenwich,
than had been obtained from 1065 chronometer exchanges during
a previous time. This method was used until the 1920's before
being replaced by radio signals.
original theodolite was built by Edward Troughton of London
during the period 1811-14, had a 24 in. circle, weighted more
than 150 lbs. and required a special oversize carriage to transport
it. In 1836 his Great Theodolite with a 30 in. circle, also
constructed by Troughton arrived in the U.S. and was put to
immediate use in the primary triangulation then being extended
east and south of New York City.
the early period, segments of the primary triangulation were
observed with 10 and 12 in. repeating theodolites and acceptable
results were obtained. The results notwithstanding, repeaters
were rarely employed on primary work after this time.
due course, several lighter, more accurate instruments were
designed and/or built in the bureau's instrument division. The
most notable being two 20 in. circle models in 1873 made by
William Wurdemann, formerly of the Coast Survey and three improved
versions of these models constructed in 1876-77 at his shops
in Dresden, Germany.
instruments were followed in the continuing evolution of smaller
and equally accurate circles at 25-30 year intervals by the
12 in. circle - 3 micrometer theodolite constructed by the then
chief of the division, Ernst G. Fischer about 1894 and the 9
in. circle - 2 micrometer theodolite designed by Douglas H.
Parkhurst, head of the division in 1927.
direction theodolites prior to the Parkhursts were read via
3 micrometers. In the early 1950's the Wild T-3 theodolite,
with a 5½ in. glass circle read by an auxiliary telescope,
replaced the 2 micrometer Parkhurst and was employed until the
mid 1980's, becoming obsolete with the introduction of the Global
Positioning System (GPS).
the more than of 150 years of U.S. triangulation observations,
diameters of horizontal circles ranged from 30 inches in the
1830's to 5½ inches in the 1980's. Despite the huge disparities
in weight, construction and diameter of theodolite circles,
the common denominator is the accuracy of the observed angles
remain the same.
of the time were built to last. Hassler's 30 in. theodolite,
for example was in constant use for about 37 years before being
destroyed by a tornado. Its destruction is described in Sp.Pub.no.7,
p.47 as follows: ..... was in continuous use till November,
1873, when it met with an accident at station SAWNEE, in Georgia.
It was struck by a tornado and, not withstanding its weight
of 300 pounds, was hurled from its stand and irreparably damaged.
Few theodolites before the Parkhursts had vertical circles attached.
Vertical angles were observed using separate instruments with
circles only slightly smaller than the horizontal ones.
to 1905 no published specifications existed for making horizontal
observations, although the procedures adopted by the superintendent
of the Survey in that year were those long in use. The lack
of stated requirements was not of great concern since only 4
or 5 observing units were in the field on any given day and
the observers, a very select group, were field trained, college-
was not always the case in later periods. Between 1935 and 1970,
for example, about 10 times that number of units often were
working on a single night.
the beginning, direction instruments were mostly employed in
a pattern of taking direct and reverse measures on each point
in turn seen by the station occupied, the sum total constituting
a set. Several sets were observed with each set beginning on
a different part of the circle. This method of observing is
attributed to Bessel, albeit it was likely used in some form
prior to his proposal.
sets became known as positions and the initial settings for
each position were assigned specific locations on the theodolite
circle. Sixteen positions evolved finally as a complete observation
for the principal triangulation with a 4" rejection limit from
Coast Survey rarely deviated from the general practice described
above, but the Lake Survey did on occasion by employing the
method of independent angles reasoning it would reduce the effects
of tower twist, a rationale dismissed by some.
Survey observers were trained to take their measures as rapidly
as possible, without forcing any of the motions or miss 'em
quick in the parlance.
information is readily available about the time required to
complete observations in earlier periods and it really doesn't
matter much because most occupations took a week or more and
a few several months. Gardens were even planted at times. Estimates
to complete the 32 pointings on each signal light when using
the 12 in.- 3 micrometer theodolite was 15-20 minutes.
Parkhursts came into use the time was reduced by about one-third
and some observers became very fast, with runs of 6-8 minutes
per light and less recorded. Similar times were the rule with
theodolites used by the C&GS prior to about 1950 required
two observers for the most expeditious operation, one to point
the instrument and read one of the micrometers and the second
to read the other micrometer(s).
assigned to observing units as recorders had to have superior
arithmetic skills so as to be able to instantly mean the 6 readings
of seconds for 3 micrometer instruments and 4 readings for Parkhursts.
Then continuing the process by reducing the readings to the
initial station for each position and placing them on an abstract
for inspection by the observer on completing his work. T-3's
involved a slightly different process, the effort required was
about the same as for the Parkhurst.
Cones, Helios, and Lights
Hassler's time, observations were generally taken on earthenware
cone targets mounted atop pole signals. Polished metal cones
for reflecting sunlight, mounted in the same fashion, continued
to be used for several decades at unmanned stations.
the 1840's, heliotropes came into use continuing until 1902
when they were replaced by acetylene lamps, which in turn were
replaced by automobile headlights in 1916. It was long known
that daytime observations caused the triangulation to sway,
probably due to unequal heating of the theodolite, despite precautions
taken against it and several attempts were made in the 1880's
to observe at night, even to using a selenotrope to reflect
moonlight; none proved too successful.
required much larger mirrors than heliotropes' 2-4 inch diameter
reflectors: i.e. 6 by 6 inch mirrors for 22 mile lines, 6 by
8 inch for 48 miles, 8 by 10 inch for 70 miles and lines longer
than these were not uncommon in the triangulation of the time.
The sway, of course could be controlled by inserting additional
Laplace stations. After 1902 all primary observations were made
plumbing of theodolites and targets over station marks is requisite
in making geodetic surveys. Exact centering was always desired,
however miscenterings of 0.1 to 0.2-in. and perhaps more when
high towers were involved would not be unrealistic, nor cause
large errors. i.e. A miscentering of 0.1-in. translate into
a maximum error of 003 in an angle over 10 mile lines and for
a 1-in. displacement, over the same length lines the largest
error would be 03. Where tripod height stands and short towers
were employed, the centering was usually done with plumb bobs.
to about 1900, when optical plummets, known as vertical collimators,
came into use, high signals were plumbed with a theodolite,
from observations at two locations, 90 or 180 apart. The early
collimators were designed for use from the top, down. Once Bilby
towers replaced wooden signals, the ease in which the tripod
head and light plate could be adjusted made it more practical
to plumb from the station mark, upward, and the collimators
were modified accordingly. Many theodolites introduced after
1950 had built in optical plummets, further simplifying the
Line Measuring Apparatus
variety of base line measuring apparatus, usually rods or bars
2-6 meters in length, encased in tubes were developed, many
ingeniously designed to resolve the problem of thermal expansion
through compensating principles. The last of these apparatus
and the most accurate, a duplex bar set was designed by Assistant
William Eimbeck in 1897 and used by him to measure the SALT
LAKE base in 1897. The equipment was employed as a field standard
replacing the iced bar apparatus used previously for the standard
kilometer section during the measurement of 9 bases on the 98th
Meridian arc by Assistant Albert L. Baldwin with steel tapes
in 1900. Eimbeck was a long time associate of George Davidson
and one of those elite mountain men mentioned previously.
first bases measured with steel tapes were the HOLTON base,
IN and the ST ALBANS base, WV by Assistants Alonzo T. Mosman
and R. Simpson Woodward in 1891 and 1892 respectively. Measurements
were made mostly at night utilizing 4 tapes, two 50 meters in
length and two 100 meters in length. A 100 meter field comparator
and a one kilometer section of each base were measured using
iced bar apparatus designed by Woodward when he was associated
with the USLS. The apparatus consisted of a 5 meter steel bar
immersed in melting ice in a Y shaped trough mounted on two
3 wheel vehicles that were moved along a portable track.
highly accurate, it was a cumbersome device requiring about
one hour to measure 100 meters. Similar equipment was long used
by the Bureau of Standards to standardize tapes. No C&GS
base line was completely measured with the apparatus. The 9
bases on the 98th Meridian arc were measured accordingly, except
only the 100 meter comparators were established by iced bar
measures, with Eimbeck's duplex bars serving as the field standard,
as mentioned earlier.
Impact of Invar
thermal expansion problem was finally resolved with the discovery
of invar, an alloy of nickel and steel having a very low coefficient
of expansion by Charles E. Guillaume, a French scientist about
the turn of the century. Tapes and wires became feasible for
the measurement of 6 primary base lines by Owen B. French in
1906, all bases were measured using tapes made of invar, 50
meters in length, a much more efficient and faster method than
those previously employed and certainly as accurate. Base line
tapes were kept in sets of 4, three for the measurements and
one as a comparator, all standardized prior to and after use.
to 1870, all primary base lines resulted from a single measurement
with segments occasionally remeasured for verification purposes.
Due to the singular nature of the observations, the validity
of the measurements was primarily ascertained by knowledge of
the equipment and procedures employed. Accuracy estimates were
based on comparisons of the apparatus made prior to and at the
completion of the work with the field standard and by duly considered
error estimates for the various observations and actions involved.
1872-73, the ATLANTA base on Peach Tree Ridge was completely
measured three times, forward in the fall, backward in the winter
and forward again the following summer. Few base lines were
ever completely measured twice prior to this time and to do
so on 3 occasions was probably a geodetic first. Later, at least
two complete measurements were made and when using invar tapes
two of the measures were always made in opposite directions
with the same person at the front contact or marking end of
the tape to cancel the parallax effect.
base lines was a time consuming chore prior to tapes being employed.
Sites often had to be graded to meet the 5% slope restriction
and taking observations at 6-8 meter intervals made for slow
progress, which averaged less than 0.5 mile per day for Hassler's
equipment and slightly more than one mile with compensating
apparatus. Once tapes were introduced, the grade allowance was
increased to 10% and the much longer tapes made 5 miles and
more progress per day routine.
line apparatus followed an evolutionary path similar to that
taken by theodolites, with one distinct exception. Each new
apparatus provided an improved accuracy, while there is no significant
difference in the angles measured with the 3 footers in 1790
and those observed by the half footers after 1950. For example:
The 3 base lines measured with Hassler's equipment had an average
standard error (one sigma) of 1:200,000; compensating apparatus
1:310,000 and invar tapes 1:675,000 or better.