PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
September 2015
687
sector of the boundary between Krogh Beacon and Mpundweni
Beacon. An Anglo-Portuguese commission re-demarcated the
sector from Krogh Beacon to Mpundweni Beacon in 1925. The
following gives the beacons from south to north with their
locations which are based on a coordinate grid system from
M’Ponduine Geodetic Station where: φ = 25° 56’ 47.19” S, λ
= 31° 58’ 40.46” E, X = 0.0 m, Y = 0.0 m; Muguene Geodetic
Station: X = –29,757.40 m, Y = +19.691.48 m; Krogh: X =
–12,756.06 m, Y = +23,576.54 m; Line: X = –12,048.39 m, Y
= +18,300.49 m; Oribi: X = –10,809.60 m, Y = +9,064.82 m;
Sikayana: X = –10,976.64 m, Y = +6,718.89 m; Xilungo: X =
–5,236.90m, Y = +5,786.62m; C: X = –3,268.72m, Y = +5,038.19
m; D’: X = –2,539.52 m, Y = +5,430.60 m; Mpundweni Beacon
(M’Ponduine Marco): X = +229.38 m, Y = +512.66 m, φ = 26° 07’
25.98” S, λ = 32° 16’ 31.58” E”
(International Boundary Study,
Mozambique-Swaziland Boundary, The Geographer, Bureau
of Intelligence and Research, U.S. Department of State, No.
135, June 4, 1973).
“At the suggestion of the Surveyor-General, Pretoria, it was
eventually decided to compile a single sheet map at 1:500,000,
utilizing not only the Irrigation Department’s topographical
map but also the cadastral survey of the Union
[of South Africa
– Ed.]
currently under preparation at 1:250,000. The result
was a single sheet map of Swaziland in four colors at 1:500,000
with a part of the imprint reading ‘Drawn in the Trig Survey
Office, Pretoria, for the Swaziland Administration.’ The map
is not dated but 500 copies were printed in March 1939. In the
course of compilation, further small failings were found with
the work of the 1905-11 survey, this time in connection with
heights of peaks on the northwest boundary.
“Cartographic developments in South Africa in the 1930s
and in the war years affected map provision in Swaziland. In
1935 the High Commissioner was informed of the intention
of the Union Department of Irrigation to prepare a contour
map of the Union including Swaziland, in 10 sheets. By 1951,
ten preliminary plots covering a priority area in Swaziland
had been issued. By 1954, twenty-two preliminary plots had
been issued, the remaining eleven were nearing completion
and contouring was receiving high priority. The heighting of
Swaziland, together with a trigonometrical survey to cover
the whole territory with a triangulation network tied to the
Union system, took longer than estimated because of adverse
observations conditions, but it was completed by December
1956”
(Geography and Imperialism 1820-1940, Morag Bell,
Manchester University Press, 1995, 338 pages).
The first Surveyor General of Swaziland was appointed
in 1973. Prior to that, land registration surveys in the
country came under the jurisdiction of the Surveyor General
of Transvaal, South Africa, and all records were kept in
Pretoria. The control framework of Swaziland was originally
established by the then British Directorate of Overseas
Surveys (DOS), and is generally strong
(Land Survey and
Large-Scale Mapping in Sub-Saharan Africa, UN Centre for
Human Settlements (Habitat), Nairobi, 2001)
.
The classical system of Swaziland is part of the Cape Datum
of 1950 where the origin point is Buffelsfontein, near Port
Elizabeth where: Φ
o
= 33º 59’ 32.000” S, Λ
o
= 25º 30’ 44.622” E,
azimuth to Zuurberg measured fromSouth: α
o
= 183º 58’ 15.00”,
ξ = –3.46”, η = –0.59”, h
o
= 280.1 m, and the ellipsoid of
reference is the Clarke 1880 where:
a
= 6,378,249.145 m, and
1
/
f
= 293.465. The Gauss Conform Transverse Mercator Grid
system has 2º wide central meridians at: 31ºE. “No arbitrary
scale factors or false origins are applied to the co-ordinates;
X is measured positive southwards from the equator and Y
positive westwards from the nearest odd meridian. The unit
of measurement since the 1970’s is the International metre”
(Chief Directorate: Surveys and Land Information, 1995,
personal communication)
.
The new geodetic datum in South Africa is termed
“Hartbeeshoek 94 Datum” and is referenced to the GRS80
ellipsoid where: a = 6,378,137. m, and
1
/
f
= 298.257222101.
The 3-parameter transformation for Swaziland is based on
four points
from
Cape Datum
to
Hartbeeshoek 94 Datum
where: ΔX = +136.8 m, ΔY = +106.6 m, ΔZ = +293.0 m. “The
seven- and four-parameter transformations provide little
improvement over the three-parameter transformation and
the scale factor cannot be separated from the translations”
(Datum Transformation Parameters in Southern Africa, Rens,
J, & Merry, C.L., Survey Review,
30
, 236, April 1990)
.
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).
STAND OUT FROM THE REST
earn asprs
certification
THE
IMAGING & GEOSPATIAL
INFORMATION SOCIETY
ASPRS Certification validates your professional
practice and experience. It differentiates you from
others in the profession.
For more information on the ASPRS Certification
program: contact
visit
