PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
April 2015
267
Sudan.” Sudan is a generally flat, featureless plain with a desert
that dominates the north
(World Factbook, 2015)
.
“Since 1899 cadastral mapping in the Sudan has been
concentrated along the banks of the Nile from the Egyptian
frontier to latitude 13º N., in the towns, and in the area of the
Gezira, south of Khartoum, where cotton has been developed.
These surveys were controlled by theodolite and steel tape either
in the formof traverses or rectangulation. The early triangulation
was used mainly to control topographical surveys, for it was
essential to cover the whole country as rapidly as possible with
a series of maps on scale 1:250,000. As a consequence much of
this early triangulation is of a relatively low order of accuracy,
indifferently marked on the ground, and unfit for inclusion in
a framework for medium and large scale mapping. Brigadier
Winterbotham’s visit to the Sudan in 1929 led however to a
revival of interest in the geodetic triangulation of the 30
th
Arc of
Meridian. Lieut.-Col. S. L. Milligankk then Director of Surveys,
made persistent efforts in face of the poverty of the country and
the economic crisis to start the great work, and a length in 1935
a party under R.C. Wakefield went into the field. Progress was
steady for five seasons and, by the time war intervened, two
sections of the chain had been completed between the Egyptian
frontier and latitude 13° 30´ N”
(Base Measurement in the Anglo-
Egyptian Sudan, D. F. Musey, M.A., Empire Survey Review, Vol.
X, No. 72, 1949, pp. 66-74)
.
Geodetic work started in the Sudan in 1935 as part of the
survey of the “Arc of the 30
th
Meridian” from Norway to South
Africa. The geodetic work in the Sudan was an extension of
previous work through Europe and ended finally in Egypt; the
origin for the Egyptian work was considered in establishing an
origin for the work in the Sudan. The fundamental origin of
the Egyptian chain is “Venus” station near Cairo. In 1874 a
number of expeditions were led by British scientists to various
European colonies in Africa and the Indian Ocean in order to
simultaneously observe the transit of Venus for the purpose
of precisely determining differences in longitude. Helwân
Observatory situated on Az Zahra Hill in the Al Moqattam
Hills, Qalyûbîya of Cairo was utilized for the observations,
and the station was termed “F
1
” where: Φ
o
= 30º 01´ 42.8591˝
N, Λ
o
= 31º 16´ 33.6˝ East of Greenwich, the initial LaPlace
azimuth being measured from Station O
1
(Helwân) to Station
B
1
(Saccara), α
o
= 72º 42´ 01.20˝ from South, and H
o
= 204.3 m,
based on mean sea-level at Alexandria. The Egyptian work was
extended to Adindanwhich is just north of the Sudan border. The
geographical positions of this station were computed according
to the Hayford figure of 1909 where:
a
= 6,378,388 m,
1
/
f
= 297.
“In Mongalla minor triangulation completed a chain from
the western limit of the survey along the Sudan-Uganda
boundary to the Nile and was connected at Opari to the 1927
survey. Various disconnected surveys, from Gwynn’s of 1901 to
Whitehouse’s of 1926, have been incorporated, and the values
of all trigonometrical stations have been re-computed. When
smoke from grass-fires caused the temporary cessation of the
Mongalla survey, the inspector moved to Upper Nile and fixed
astronomically some positions between the Nile and the Pibor
at the request of the Egyptian Irrigation Department; latitude
observations were made to a minimum of twenty pairs of stars,
and longitude was determined by wireless time signals. Five
new trigonometrical stations were fixed in the Nuba Mountains,
and the position of Dilling was found by Astro-radio means to
differ from that previously accepted by 7.01˝ in latitude and
29.106˝ in longitude. In a minor triangulation in the Hadendowa
District of Kassala a base of 7,000 metres was measured near
Tendera Wells and connected to Jebels Asoteriba and Musmar,
which were fixed in 1902. A native surveyor was sent to make
a plane-table survey in the Qala’ en Nahl neighbourhood and
measured a base of 3,500 meters along the Sennar-Gedaref
railway, connecting up to Jebel Beila fixed by Gwynn in 1904”
(Sudan Government: Annual Report of the Survey Department
for the Year 1930, Empire Survey Review, pp. 139 & 140)
.
For the Sudan part of the arc, the origin of the geodetic
work was in southern Egypt near Abu Simbel, south of Lake
Nasser, at station Adindan where: Φ
o
= 22º 10´07.1098˝N,
Λ
o
= 31º 29´21.6079˝ East of Greenwich, azimuth of line Z
v
– Y
v
: α
o
= 58° 14´ 28.45˝, deflection of the vertical:
ξ
= +2.38˝,
η
=-2.51˝, and the ellipsoid of reference was the Clarke 1880
(modified)
where:
a
= 6,378,249.145 m and
1
/
f
= 293.465. The
Blue Nile Datum of 1958 is the established classical datum
of Sudan and much of North Africa. Adindan is the name of
the origin, it is not the name of the datum; a most common
mistake found in many “reference works.”
In the period between 1935 and 1945 all the geodetic work
in the Sudan was concentrated on the Arc of the 30
th
Meridian
as it would be the basis for the whole program. During
this period, the arc was carried south to latitude 13° 45´ N.
Throughout this work, the English-made Tavistock theodolite
was used in the observations with sixteen sets of angles
observed
(A Geodetic Datum for The Sudan, M.O.Adam,
Cornell University Thesis, June,1967, 95 pages)
.
The other part of the Arc of the 30
th
Meridian from
latitude 13° 45´ N to the boundary with Uganda was observed
together with a number of first and second order chains
during the period 1943 to 1952. Assistance on this work
was given by the U.S. Army Map Service; one Party Chief
was the late William Parkhurst that used a Wild Heerbrugg
theodolite and moved from place to place via camel
(Personal
communication, c.a. 1963)
.
Based on a
very
recent analysis of 13 collocated points in the
Sudan, the 3-parameter transformation
from
WGS84 datum
to
the Blue Nile Datum of 1958 (Adindan origin) has updated
the NIMA values to
Δ
X = +162.6 m ± 0.3025 m,
Δ
Y = +15.1 m ±
0.3025 m,
Δ
Z = –204.5 m ± 0.3025 m; RMS = 1.0906 m
(Common
Point Coordinates Transformation Parameters Between
Adindan (Sudan) New Ellipsoid and the World Geodetic System
1984 (GPS Datum) Coordinates Compared with Parameters of
the American National Imagery and Mapping Agency (NIMA),
Abdelrahim Elgizouli Mohamed Ahmed, International Journal
of Advanced Research in Engineering and Applied Sciences,
ISSN: 2278-6252, Vol. 2, No. 9, September 2014, pp. 26-39)
.
The contents of this column reflect the views of the author, who is
responsible for the facts and accuracy of the data presented herein.
The contents do not necessarily reflect the official views or policies of
the American Society for Photogrammetry and Remote Sensing and/
or the Louisiana State University Center for GeoInformatics (C
4
G).
