338
May 2017
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
in Africa. This was the same rationale as had already been
established by Everest 100 years prior in India. The goal was
for “continuous British pink on the map from the Cape to
Cairo.” The classical triangulation of the 30
th
Meridian arc has
its roots both in South Africa that extended northward from
the Cape and also southward from British Central Africa.
The Cape Datum has its initial origin point in Port
Elizabeth, South Africa, at station Buffelsfontein where: Φ
o
=
33° 59´ 32.000˝ South, Λ
o
= 25° 30´ 44.622˝ East of Greenwich.
The ellipsoid of reference is the Clarke 1880, where: a =
6,378,249.145 meters,
1
/
f
= 293.465. The azimuth to station
Zurrberg is: α
o
= 004° 15´ 26.311˝, and the geoidal height
(H
o
- h
o
) at the origin is defined by implication to be zero.
The deflection of the vertical at Buffelsfontein was initially
assumed to be zero, and although non-zero values were
subsequently published in the middle 1960s, this has been
ignored. The Cape Datum theoretically covers a substantial
portion of South East Africa, but has been subjected to several
regional adjustments that effectively separate into a variety
of individual local systems. The countries surrounding
Moçambique that are on the Cape Datum include South
Africa and Swaziland.
The Arc Datum has the same origin as the Cape Datum, but
its initial fieldwork started in Uganda and Kenya. Individual
country adjustments of this meridional chain (or arc) of
quadrilaterals have resulted in the countries surrounding
Moçambique that are on the Arc Datum to include Tanzania
which is on the Arc Datum of 1960. This particular adjustment
is carried further north into the Sudan. Malawi, Zambia, and
Zimbabwe are on the Arc Datum of 1950. Note that Zimbabwe
was formerly Southern Rhodesia, Zambia was formerly
Northern Rhodesia, Malawi was formerly Nyasaland, and
Tanzania was formerly Tanganyika, which had been formerly
Ger-man East Africa. After World War I, the British assumed
colonial administration of Tanganyika. The consequence of
this was that Moçambique was now surrounded by British
colonies, and its borders were subsequently entirely surveyed
by the British Royal Engineers.
The Moçambique–Tanzania boundary initially delimited
German and Portuguese spheres of influence in East Africa.
In accordance with the terms of a German-Portuguese
declaration signed at Lisbon in 1886, a boundary was
established between the Indian Ocean and Lake Nyasa.
Subsequent treaties delimited the boundary in additional
detail, and a joint expedition in 1907 changed the boundary
slightly in the west and demarcated the land segment by
pillars. Following WWI, the former German territory of
Tanganyika was made a British mandate, and during 1936
and 1937 an exchange of notes between Portugal and the
United Kingdom determined the sovereignty of the island
in the Rio Rovuma (Ruvuma River) which forms more than
90 percent of the total boundary. With a total length of 752
km (470 miles), streams comprise 712 km (445 miles) of the
distance of which the Rio Rovuma and its tributaries account
for all but about 1½ km (1 mile). The Rule of the Thalweg
(thread of the stream) is specified for this riparian boundary.
The parameters published by DMA/NIMA for the Tanzania
Arc 1960 Datum to WGS84 are: ΔX = –175m ± 6m, ΔY = –23
m ± 9m, ΔZ = –303 m ±10m.
The Moçambique–Malawi boundary is approximately 1560
km (975 miles) in length and was originally demarcated in
1899-1900 with errors. It traverses Lake Nyasa for about
328 km (205 miles) including lines around Likoma Island
and Chisumulu Island, which are part of Malawi. Southward
from Lake Nyasa to the Malosa River, the boundary extends
along straight-line segments for 312 km (195 miles) passing
through both Lake Chiuta and Lake Chilwa. It follows
consecutively the thalwegs of the Malosa, Ruo, and Shire
rivers downstream for 240 km (150 miles). The boundary
then continues northwestward to the Zambia tripoint
utilizing features along the Shire-Zambezi and the Lake
Nyasa-Zambezi drainage divides for most of the remainder
of the distance. The parameters published by DMA/NIMA for
the Malawi Arc 1950 Datum to WGS84 are: ΔX = –161m ±
9m, ΔY = –73 m ±24m, ΔZ = –317 m ±8m.
The Moçambique–Zambia boundary commences in the
Northwest at the tripoint (with Malawi) where the Lake
Nyasa–Zambezi River drainage divide meets at the 14th
parallel in accordance with the agreement of June 11, 1891
between the United Kingdom and the Kingdom of Portugal.
The tripoint was determined to be located at
f
= 14° 00´ 00˝
S,
l
= 33° 14´ 32˝ E by a joint boundary commission in 1904.
The commission was led by Captain (later Admiral) Carlos
Viegas Gago Coutinho of the Portuguese Navy and by Major
O’Shee of the United Kingdom. The boundary proceeds to
the southwest along the Zambesi River drainage divide
until it meets the River Aroangwa or Luangwa. Thence, the
boundary follows along that river until it meets the Zambesi
River to tripoint (with Zimbabwe) Beacon Number 1 where:
f
= 15° 37´ 27˝ S,
l
= 30° 25´ 20.3˝ E. Note that Zambia is
where the Livingstone Memorial is located. (“Dr. Livingstone,
I presume …?”) The parameters published by DMA/NIMA for
the Zambia Arc 1950 Datum to WGS84 are: ΔX = –147m ±
21m, ΔY = –74 m ±21m, ΔZ = –283 m ±27m. Coutinho and
O’Shee later spent 1904-1905 correcting and re-marking the
border north of the “14°S” Malawi tripoint.
The Moçambique–Zimbabwe boundary is about 1224
km (765 miles) in length. It is demarcated throughout this
distance by pillars or rivers. The tripoint (with Zambia)
Beacon Number 1 addressed in “The Northern and Southern
Rhodesia Order in Council 1963” indicated that their
common boundary joined the Moçambique tripoint at the
medium filum acquae
(median line) of the Zambesi River.
This is very close to the Moçambique village of Zumbo,
where the old Madzansua Datum origin is located. In the
central part, the boundary traverses an area of numerous
