PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
June 2020
351
by
Clifford J. Mugnier, CP, CMS, FASPRS
I
nhabited since Paleolithic times, the beginning
of Vietnamese civilization dates back to the
late Neolithic or early Bronze Age. Vietnam is
tropical in the south and subject to monsoons in the
north. The country is low, comprised of the Mekong
Delta in the south, the Red River Delta in the north,
central highlands, hilly, mountainous in the far
north and northwest. The lowest point in Vietnam
is the South China Sea; the highest is Ngoc Linh at
3,143 meters. The area of Vietnam is slightly larger
than New Mexico; with a 3,260-km coastline, its
maritime boundary had been established according
to the “Straight Baseline” principle. Vietnam is
a poor, densely populated communist state that
has had to recover from the ravages of war, the
loss of financial support from the old Soviet Bloc,
and the rigidities of a centrally planned economy.
Independence Day is 02 September (1945).
France had occupied all of Vietnam by 1884 and remained
for the most part until 1954. Longitude was determined in
Haïphong by Héraud and Bouillet, hydrographic engineers, in
1874. The longitude was deduced from the time transfer from
Saïgon; two chronometers were used for the first traverse
and five chronometers were used between the observatory at
Haïphong and the observatory of Saïgon. It is interesting to
note that by 1883, Hong Kong and Haïphong were connected
by submarine cable. The longitude of Hong Kong had been
determined in 1881 by telegraph, so it was deduced that
the longitude of Haïphong was now determined to a better
precision than was determined by the use of chronometers.
In 1886, Héraud measured the baseline in Haïphong between
Grand Mirador and Petit Mirador to be 4,312.8 meters.
“The observatory in Haïphong was established to observe
the longitude difference. It was essentially comprised of
a masonry pillar constructed on a solid foundation, and a
grass hut was constructed of bamboo.” The position observed
The Grids & Datums column has completed an exploration of
every country on the Earth. For those who did not get to enjoy
this world tour the first time,
PE&RS
is reprinting prior articles
from the column. This month’s article on the Socialist Republic
of Vietnam was originally printed in 2002 but contains updates
to their coordinate system since then.
THE SOCIALIST REPUBLIC OF
VIETNAM
in 1874 was Φ
o
= 20° 51´ 43.5˝ N and Λ
o
= 104° 20´ 30˝
East of Paris or 106° 40´ 43.95˝ East of Greenwich. These
observations were the initial determinations that later
would provide the defining datum for the northern part of
Vietnam. Grand Mirador was defined as the position of the
geodetic net (Position du réseau géodesique indochinois)
where Φ
o
= 21° 01´ 58.415˝ N and Λ
o
= 109° 00´ 57.90˝ East
of Greenwich. The azimuth from Grand Mirador to Nui Deo
is α
o
= 334° 29´ 49.8˝. The ellipsoid of reference is the Clarke
1880 where
a
= 6,378,249 m and
1
/
f
= 293.46. The subsequent
transferred origin of the grid for Signal Grand Mirador was
j
o
= 20° 42´ 24.337˝ N and
l
o
= 106° 46´ 29.282˝ East of
Greenwich. The False Easting and False Northing for this
Hatt Azimuthal Projection were each equal to zero. There were
Photogrammetric Engineering & Remote Sensing
Vol. 86, No. 6, June 2020, pp. 351–353.
0099-1112/20/351–353
© 2020 American Society for Photogrammetry
and Remote Sensing
doi: 10.14358/PERS.86.6.351
