394
May 2014
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
now recognized as a significant insight into early Tongan
life, customs and culture. Another navigator to visit Tongan
waters was Captain William Bligh, and Fletcher Christian’s
infamous mutiny of the HMS Bounty actually occurred near
the volcanic island of Tofua in the Ha’apai group. In 1845, the
scattered and pristine islands of western Polynesia became
united as the Kingdom of Tonga, and 30 years later officially
became a constitutional monarchy and British Protectorate.
The first King of this united Tonga was George Tupou I,
and the modern Kingdom of Tonga is the only Pacific Island
nation never to lose its indigenous governance or to be
colonized. Located just west of the International Date Line,
Tonga is also the first country to experience the new day
each morning. Tonga joined the Commonwealth of Nations
in 1970, jettisoning the protectorate status in 1970, but
still retaining its unique position as the only monarchy in
Polynesia”
(
2011 Tonga Visitors Bureau
)
.
Four times the size of Washington, D.C., the terrain of the
islands is mostly comprised of a limestone base formed from
uplifted coral formations; others have limestone overlying a
volcanic base. The lowest point is the Pacific Ocean (0 m); the
highest point is an unnamed elevation on Kao Island (1,033
m). The Kingdom of Tonga is an archipelago of 169 islands, 36
of which are inhabited
(World Factbook, 2014)
.
“
Old survey records indicated that surveying and mapping
in Tonga began somewhere around in the early years of the
1900s onwards. Up until 1927, at least three to four expatriate
surveyors from Australia and New Zealand, assisted by only
few locally trained field surveyors were consistently employed
by the Tonga Government to carry out the required survey
works. These included coastal traverses, road and engineering
surveys, land boundary surveys for hereditary estates,
townships and new individually granted allotments (town and
tax allotments – at standard legal sizes) were carried out in
most parts of the main islands of Tonga – at a steady rate of
progress due to shortage of trained personnel. This was the
situation during and after the 1
st
World War in 1918. In 1927,
it appeared that the size of the field survey forces and their
annual outputs were nowhere close to meeting the demands
from a rapidly increasing population for more subdivided lands
- tax and town allotments. However, during the period 1927
– 1957 a large amount of surveyed tax and town allotments
were completed due to increasing number of Tongan overseas
trained Surveyors (at technician level) that returned and were
employed permanently by the Government of Tonga. Although
the bulk of the survey works, completed for the period 1900 –
1957, were of good standard theodolite traverses, various and
different meridians were used as origins and occasionally a
true meridian was used. Bearings of contiguous surveys in an
area were usually in the same terms, but no system of regular
coordinates was set up as a survey and mapping basis for the
completed works”
(Folau, V. & Malolo, T.L., A Report on the
Geodetic Infrastructure of the Kingdom of Tonga, Ministry of
Lands, Environment, Climate Change and Natural Resources,
Kingdom of Tonga, September 2013, Fiji)
.
Classical datum origins consist of “Astro Stations” in
Tonga, all referenced to the International Ellipsoid where
a
=
6,378,388 m and,
1
/
f
= 297.
Vava’u
(Datum Origin?) is at
Trig
B
where: Φ
o
= 18º 37’ 28.93” S, Λ
o
= 174º 03’ 59.82” W, α
o
= 64º
11’ 47.0” to
Trig A
from North.
Nomuka
Datum of 1959 Origin
is where: Φ
o
= 20º 15’ 15.5” S, Λ
o
= 174º 48’
??.?
” W, α
o
= 119º
28’ 29.8” to
Toafa
from North.
Pangai
Datum of 1961 Origin
is at
Trig I
where: Φ
o
= 19º 48’ 20.7” S, Λ
o
= 174º 20’ 56.3” W, α
o
= 232º 02’ 37.0” to
Trig II
.
Tongatabu
Datum of 1942
(noted
in the 1980s that this might not be used by the Kingdom of
Tonga)
Origin at South Station where: Φ
o
= 21º 03’ 23” S, Λ
o
=
175º 15’ 36” W, α
o
= 206º 06’ 09.3” to
North Station
, observed by
the U.S.S. Sumner
(John W. Hager, personal communication 5
May 2005)
. The majority of the above datums are collectively
known as the Tonga Cadastral Survey Datum 1957-1961
(TCSD57/61).
“ The above Survey Operations were executed by Leach
and Browne, Registered Surveyors, Milford in Auckland, New
Zealand. The Tonga Cadastral Survey Datum (TCSD 57/61)
and as well as the Tonga Cadastral Survey Grid (TCSG 61)]
was established at four island groups, each with its own
circuit origin and azimuth determination. The four circuits
are:
Tongatapu/’Eua, Nomuka, Ha’apai and Vava’u
. The
purpose
of the survey control network or circuit was to provide
a homogenous framework from which to survey and subdivide
land parcels into town and tax allotments of 8¼ acres each. The
area of 8¼ acres is based on a land parcel having the nominal
dimensions of (100 fathoms × 100 fathoms). An instruction
manual, titled
“Instructions for the Cadastral Survey of the
Kingdom of Tonga”
, was produced in 1958 by Leach and
Browne, Reg. Surveyors, Milford in Auckland, NZ; which also
established cadastral survey and office procedures for recording
land registration information. A report title
“General Notes on
the Primary Control for the Cadastral Survey of Tonga”
was
produced and signed by D. L. Leach himself.
“The Tonga Cadastral Survey Grid 1961 (TCSG 61)
Definition: Map Grid System – TCSG 61, Projection –
Transverse Mercator based on the UTM Projection Zone One,
Unit of Measurement: For UTM. Meter (1m = 3.2808455 ft.)
For TCSG 61, Link (100 links to 1 chain or 66 ft.), True Origin
– The true origin of the UTM Zone One is the intersection of
the Central Meridian (CM) of 177º West Longitude with the
equator. The coordinates of this origin are 500,000 meters
East and 10,000,000 meters North. False Origin –
the origin of
the TCSG 61 is a point on the 177º West Longitude, which has
a UTM Northing coordinate value of 7,500,000 meters North.
There is therefore a direct relation between the UTM Zone One
projection coordinates in meters and the TCSG 61 projection
coordinates in links. Scale Factor –
the Scale Factor at the CM
is k o = 0.9996 (a reduction of 1 = 2,500).
“In remote and isolated islands or group of islands not
covered during the Cadastral Survey Operations, Directorate
of Overseas Surveyors established six more additional Survey
Control Circuits and Datums (Horizontal and Vertical),
