Coast and Geodetic Survey (Retired)
12934 Desert Glen Drive
Sun City West, AZ 85375-4825
direction theodolite is certainly among the 4 or 5 greatest
technological advances ever in geodetic surveying. As a
case in point, prototypes continue in use by almost all
countries. In the field of general surveying however, the
invention by the French of the repeating theodolite about
1790 is of equal importance for it is the basis for the
instrument most surveyors have employed. Regardless of their
almost universal use in the private sector, repeaters have
been shown to be less accurate than direction instruments.
In theory, the opposite is the case, in practice however,
repeaters' more moveable parts and mechanical motions required
to operate them contribute to larger error sources.
for the French, as you might expect they still preferred
repeating theodolites for higher order surveys as late as
1963 when a new connection between England and France was
made. Instruments employed that year were repeating types,
presumably reading to 1" with eye pieces having moveable
cross hairs so that as many as 10 readings could be obtained
from each pointing. One point of interest. This new connection
between Portsmouth and Cherbourg was only possible because
Bilby towers were available.
might be anticipated The Netherlands established the first level
datum in 1682 and carried out surveys along rivers and some
shoreline between 1797 and 1812. However, the first geodetic
leveling was not begun until 1875. By contrast, Great Britain
started their geodetic leveling in 1841 and completed it about
20 years later. In almost all instances geodetic levelings were
undertaken after the triangulation was well on its way or completed.
1800, most of the countries of Europe had drawn up plans
or were on their way in establishing triangulations that
in 1842 spanned the continent from the Mediterranean Sea
on the south to the Arctic regions on the north and from
Ireland, England and the Atlantic Ocean on the west to the
interior of Russia on the east.
R. Hassler -- The Founder
United States entered this world of geodesy in 1807 and
while 25 years passed before the primary work could be initiated,
its achievements were soon recognized by much of the world.
At the beginning and along the way for 25 years however,
there were many trials and tribulations to be overcome.
The country was very fortunate indeed that a man of the
caliber of Ferdinand R. Hassler was selected to lead the
effort for one of lesser resolve would have given up early,
the problems were many and difficult. Hassler was 37 years
old when he was named the first superintendent of the Survey
of the Coast and 62 when he began the first major triangulation
in 1832. There were many depressing and disillusioning periods
for him in the intervening years.
1807-1940 period is divided into three sections: The Early Years
1807-1843, Laying the Foundations of the Networks 1843-1900
and Building the Networks 1900-1940. Some of the material such
as that related to instruments and computations is given intoto
in one section or another even though the period covered spans
two or more sections. Also, the brief histories for Geodetic
Astronomy, Gravity and Reconnaissance Surveys cover the years
EARLY YEARS 1807-1843
Survey of the Coast Created
surveying began in the United States on February 10, 1807
with the creation of the Survey of the Coast by Congress
in the presidency of Thomas Jefferson. Ferdinand R. Hassler,
a Swiss born geodesist, who conceived the plan was placed
in charge and served in that capacity on and off until his
death in 1843. Nothing was accomplished for several years
because appropriated funds were not released due to political
opposition and unsettled conditions in Europe, the source
of needed equipment. Finally in 1811, $25,000 was disbursed
and Hassler immediately went to England to have instruments
made to his design and specifications and to purchase other
equipment and scientific books. He remained there during
the War of 1812, returning in 1815.
field surveys were carried out in 1816-17 near New York
City where a small scheme of triangulation consisting of
11 points, scaled by two measured base lines was accomplished
to an accuracy that would approach present day second-order,
class I. Hassler performed the reconnaissance to select
the station sites, directed the base line measurements and
observed all the angles with the recently acquired 24 in.
theodolite, built by Edward Troughton of London to his specifications.
first point occupied for geodetic observations in the U.S.
was identified as WEASEL located on a low mountain about
2 miles south of Patterson, NJ on July 16, 1817. It was
marked by a 6" deep drill hole filled with sulphur. In 1934,
it was reported that the top of the mountain had been blasted
off destroying the station. Blasting is among the very few
ways to obliterate a mark of this type.
of the original stations are thought to exist today, although
WEASEL and SPRINGFIELD were included in the primary triangulation
southward from NYC observed in 1838. Station CHERRY HILL,
one end of the base line at the northern end of scheme,
near Englewood, NJ was destroyed by sub-division construction
in the late 1970's only a few days before personnel were
scheduled to move the point to a protected area. In 1987,
the American Society of Civil Engineers placed a plaque
at the approximate location of original station CRANETOWN,
north of Montclair, NJ, noting the site as a National Historic
Civil Engineering Landmark.
immediately on its completion, politics reared its ugly
head once again and Hassler was dismissed. For about 15
years he tried his hand at several occupations before being
reappointed to his position in 1832. First he worked as
an assistant on the U.S.-Canada northeast boundary surveys,
then made an unsuccessful attempt at farming in a remote
site on the St. Lawrence River where his wife left him.
After that he took a position as a gager at the NY Custom
House, followed by a period of unemployment during which
he wrote several books on advanced mathematics and developed
the polyconic map projection still used today. Finally in
1830, he received an appointment as superintendent of the
new Office of Weights and Measures. This office remained
in the Coast and Geodetic Survey until 1901 when it was
spun off to become the National Bureau of Standards. This
was a dark period for both Hassler and American geodesy.
back on the job he immediately began geodetic surveys on
Long Island, NY that have continued, more or less unabatedly
until today. The instruments and equipment that Hassler
had made or purchased were more than adequate for the task
at hand. This was attested to by a French astronomer who
said in 1832 --- at the time of construction, the instruments
were twenty years in advance of the science of Europe. Having
the best of tools is no guarantee, of course for the best
of results. In surveying best means the most accurate and
to reach that goal requires, in addition to the instrumentation,
trained and conscientious personnel and proper observing
procedures. The sum total of all the requirements can be
broadly categorized as standards of accuracy. In that regard,
Hassler set standards of highest accuracy for these early
surveys that remain the hallmark of American geodetic work.
personally made all the observations at the primary stations,
yet at the same time trained his assistants James Ferguson
and Edmund Blunt on the secondary surveys so that they could
step in when necessary to do his job --- and they did. In
the year after Hassler's death in 1843, Ferguson measured
the KENT ISLAND base line in Maryland, Blunt the MASSACHUSETTS
base, and they shared his role in observing the primary
first station occupied was BUTTERMILK on June 11, 1833.
It still exists and is located on what is now the Rockefeller
estate in Westchester County, NY.
to October 18, 1836, the observations were made using the
24 in. theodolite mentioned previously. On that day and
until his death in 1843, he employed a 30 in. instrument
that he proudly called the Great Theodolite. Designed by
himself, built by Troughton, the finest instrument of its
day was used first at station WEST HILLS on the northern
shore of Long Island, a point that remains in place even
now. Its weight of 300 lbs. was of little concern to Hassler,
having used a 36 in. Ramsden theodolite, an instrument of
similar weight in the trigonometrical survey of Switzerland.
He simply strengthened the oversize carriage used for transporting
the 24 in. instrument, a fairly heavy piece in itself weighing
perhaps 200 lbs.
characteristics of the Great Theodolite are seldom mentioned,
one, it was designed as a repeating instrument and two,
it had a 24 in. vertical circle. Hassler employed it in
the direction mode as did others later, until destroyed
in 1873 and it must be assumed that the final construction
was as a direction theodolite.
two base lines measured for the 1816-17 survey at Gravesend
Bay near present day Coney Island (4.7 mi) and at Englewood,
NJ (5.8 mi) were not considered accurate enough nor probably
long enough to scale the primary triangulation then underway.
Both bases were measured with iron chains, each link one
meter in length. Accordingly, Hassler measured his only
primary base line at Fire Island on the south shore of Long
Island in 1834 using four 2 meter iron bars laid end to
end. It was not a direct measurement. In order to take advantage
of the level beach, the principal measurement followed a
route from WEST BASE somewhat southerly of the direct line
to a point about 255 meters west of EAST BASE. The point
was connected to EAST BASE by angle and distance with the
distance between the terminals obtained by computation.
methods were acclaimed by several scientific societies,
but as always the real proofs of the pudding are the agreements
with the nearest base lines as computed through the triangulation.
The checks were excellent, about 1:100,000 with the MASSACHUSETTS
base, EPPING base, ME and KENT ISLAND base, MD, measured
in 1844, 1857 and 1844 respectively and about the same accuracy
with nearby EDMI lines observed in the 1970's.
base apparatus was used for the MASSACHUSETTS and KENT ISLAND
bases. The EPPING base was measured with the Bache-Wurdemann
compensating equipment. The FIRE ISLAND base is 8¾
miles in length and marked at the terminals by red sandstone
monuments 4 ft. high and about 1 ft. square with a rounded
top and at intervals of 2,000 meters by stoneware cones.
Records state the marks are lost, however it is unlikely
that much of an effort was made to find them, especially
the intermediate ones. With today's equipment it wouldn't
take a huge effort to settle the question once and for all
FIRE ISLAND base was computed through the triangulation
to the line WEST HILLS - RULAND on the north side of Long
Island, a line Hassler called his mountain base from which
the triangulation east and north and to the south was extended.
This triangulation eventually ran from Calais, ME southward
to Dauphin Island near Mobile, AL then westward to New Orleans,
LA a distance of 1,623 miles with the field work done between
1833 and 1898.
Coast Survey was not the only agency establishing triangulation
at the time. In 1830 the Massachusetts legislature decided
to prepare maps of the commonwealth based on a trigonometric
survey. Colonel James Stevens was placed in charge and began
operations including the measurement of a 7.4 mile base
line along the Connecticut River, near Northampton.
measurement was carried out with compensating apparatus
50 ft. in length designed by Dr. Joseph Rice. No other information
is available about Joseph Rice and little is known about
his apparatus although the methodology was reported in one
or two scientific journals. Nevertheless, the principle
he employed was about 15 years ahead of its use in the Coast
Survey, albeit his work was known there. The first application
of the compensation principle was by the Ordnance Survey
of Ireland on the Lough Foyle base in 1827.
theodolite on loan from the Coast Survey was used for angle
observations until its recall in 1834. After that time an
instrument of their own design was employed. Stevens resigned
in 1834 and Simeon Borden, formerly an assistant took over
with the bulk of the work still to be done and completed
the survey in 1838.
results were not published until 1846 and the positions
were given as tangent plane coordinates based on the location
of the points in one of 5 zones. This was the first use
of plane coordinates on a large scale in America. In 1935
it was reported that little use was made of the coordinate
system, a situation not too different from that found today.