PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
December 2018
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ford 1909 where the semi-major axis, a = 6,378,166.0 meters,
and the reciprocal of flattening,
1
/
f
= 297. The deflection of the
vertical and geoid separation were defined to be zero at the or-
igin. Interestingly, a later adjustment performed for the Pro-
visional South American Datum of 1956 only changed the azi-
muth from station Loma Quintana to station Volcán to 316° 01´
50.30˝, which is quite a testimonial to the superb quality of the
initial work. The original Loma Quintana Datum of 1911 was
comprised of chains of quadrilaterals that eventually spanned
the entire northern coast of Venezuela from the border with Co-
lombia in the west to include the Island of Trinidad in the east.
The only national projection associated with the Loma Quin-
tana Datum of 1911 is the Compensated Secant Conic. Origi-
nally published in 1940 by the Dirección Cartografía Nacional
(National Cartographic Office), I became aware of the projection
tables in 1980. Used for the topographic mapping, it is defined
with a Central Meridian
λ
o
= –67 30´ W, and standard parallels
of
j
N
= 9º N and
j
S
= 4º N. This system baffled me for many
years because I was unable to compute Lambert conformal conic
developed meridianal distances to match the published tables.
In June of 1988, the late John P. Snyder wrote to me and point-
ed out that he had found the same tables at the U.S. Library of
Congress and the projection was actually the Equivalent Conic
and not what I had thought to be the Lambert Conformal Conic!
I subsequently discovered a constant+18.027 meter error in all
of the tabulated developed meridianal distances. The nut was
finally cracked with John P. Snyder’s help.
Also associated with the Loma Quintana Datum of 1911
(LQD 1911) are the “Oil Grids” developed in association with
petroleum exploration and development activities. This collec-
tion of Polyhedric plane projection coordinate systems has un-
derstandably baffled novices and experts alike for almost a cen-
tury. There are four major families of Oil Grids referenced to the
LQD 1911: Maracaibo, Barcelona, Maturín, and Dabajuro. The
Maracaibo Grid Family
consists of: the Maracaibo Cross Grid
(1945-1981), Cruz Morillo Grid (1917-1983), Altagracia Church
Grid (1920-1951), Alto de Escuque Grid (1957), Bloque B Grid
(1953-1954), Boca Grita Grid, El Cubo Grid (1916-1961), Mene
Grande Grid (1914-1982), El Mojón Grid (1927-1930), Monu-
ment “A” Río de Oro Grid, La Rosa Grid (1917-1982), El Mene
de Marua Statue Grid (1927-1972), Iglesia de Santa Barbara
Grid (1915-1986), Plaza Bólivar de San Cristóbal Grid (1939-
1955), and the Barinas Grid (1953-1970). The
Barcelona Grid
Family
consists of: the Barcelona Grid (1913-1920), Plaza de
Calabozo Grid, Chaguaramas Grid, Clarines Grid (1949-1958),
Punzón Grid, Sabana de Uchire Grid, Santa Maria de Ipire Grid
(1939-1974), El Sombrero Grid, Valle de la Páscua Grid (1939-
1982), Areo Grid, Barbacoas Grid (1948-1980), and the Barinas
West Base Grid (1946-1980). The
Maturín Grid Family
con-
sists of: the Maturín Grid (1918-1988), Irapa Grid, Tucupita
Grid (1939-1966), Uracoa Grid (1966), and the Chaguamaral
Grid (1955). The
Dabajuro Grid Family
consists of: the Daba-
juro Grid (1921-1963), La Vela de Coro Grid (1924-1981), Piritú
Grid (1949), Iglesia Valera Grid (1928), and the Pedregál Grid.
Every one of these Grids is on the Polyhedric Projection, which
is mathematically identical to the Local Space Rectangular sys-
tem used in computational analytical photogrammetry.
Other grids associated with the LQD 1911 include the Ven-
ezuelan Gauss-Krüger Transverse Mercator where the Cen-
tral Meridian
λ
o
= –63° 10´ 48˝ W, the False Northing Lati-
tude of Origin (
j
FN
) = 9° 45´ 02˝ N, the Scale Factor at Origin
(m
o
) = 0.9996 (same as UTM), and both the False Eastings
and False Northings are 200 km. The Lake Maracaibo Tan-
gent Lambert Conformal Conic Grids are defined with a Cen-
tral Meridian
λ
o
= –71° 36´ 20.224˝ W, the False Northing
Latitude of Origin (
j
FN
) = 10° 38´ 34.6780˝ N, the Scale Fac-
tor at Origin (m
o
) = 1.0 where the Latitude of Origin is
j
o
=
10° 10´ 00˝, and
both
the False Eastings and False Northings
are
either
200 km or 500 km, depending on the oil company.
The Cartografia Nacional signed a cooperative agreement
with the Inter American Geodetic Survey (IAGS) in 1948.
The following year the Director of La Dirección de Car-
tografía Nacional, Dr. Adolfo C. Romero, initiated the gravi-
metric survey of the origin point and vicinity of the planned
Provisional South American Datum of 1956 (PSAD56). The
origin was in the town of La Canoa, Anzoátegui Province,
Venezuela where
Φ
o
= 08° 34´ 17.170˝ North,
Λ
o
= –63° 51´
34.880˝ West of Greenwich, and the defining azimuth to sta-
tion Pozo Hondo (
α
o
) = 40° 22´ 45.96˝. Subsequent relative
gravity surveys were performed at many of the origin points
for the Polyhedric Grids. The triangulation net of Venezuela
was extended to its borders, and connections were made with
Colombia to link to the Bogotá Datum of 1948. Subsequently
the entire collections of chains were recomputed in a simul-
taneous adjusment that formed the basis of the PSAD56 that
was conveniently referenced to the Hayford 1909 (Interna-
tional 1924) ellipsoid. The Compensated Secant Conic pro-
jection was dropped, and the Universal Transverse Mercator
was adopted as the standard grid for the new datum.
In the early 1980s, an enormous hydrocarbon field was dis-
covered off the eastern coastlines of Venezuela and Trinidad.
Although a treaty existed between the two sovereign nations for
the division of the mineral resources of the continental shelf, the
treaty only covered the Gulf of Paria – not the Atlantic Ocean.
The coordinate systems of the region were known to be unusual-
ly complex; Trinidad and Tobago utilized both the Old Trinidad
Datum of 1903 with the Cassini-Soldner Grid and the Napari-
ma Datum of 1972 with the UTM Grid, and Venezuela utilized
both the Loma Quintana Datum of 1911 with the Compensat-
ed Secant Conic and the Provisional South American Datum of
1956 with the UTM Grid. Furthermore, PSAD56 was known to
exist in parts of Trinidad also. Registering various maps of the
region to each other was a cartographic nightmare of disparate
grids and datums. The prospect of a new boundary treaty (with
coordinates) being signed between the two countries without
prior
documentation of the relation of the various coordinate
systems was disturbing to contemplate.
I was retained to travel to the region and acquire the neces-
sary data to compute the relations among all existing classi-
cal coordinate systems in late 1986. Since boundary problems
