PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
August 2019
539
timated to be ±15 m in Eastings and ±4 m in Northings. The
Niutao TM Local Grid is based on the Transverse Mercator
projection where the Latitude of Origin is at the equator (
j
o
=
0°), the Central Meridian
l
o
= 177° 20´ E, the False Easting =
30 km, and the False Northing = 5,000 km. The Scale Factor
at Origin is unity (
m
o
= 1.0).
The atoll of Nukulaelae is the easternmost of the Tuvalu is-
lands and was the first island to accept Christianity. Because
of rising sea level, Nukulaelae is threatened by salt water
seeping into the taro swamps. For Nukulaelae, the origin of
the Nukulaelae Astro Datum of 1965, actually on Fanagua
Island, is unknown, but the ellipsoid of reference is the In-
ternational 1924. From the Nukulaelae Astro Datum of 1965
to the WGS84 Datum, ∆X = +254 m, ∆Y = –238 m, and ∆Z =
–234 m; the accuracy of this transformation is estimated to be
±13 m in Eastings and±14 m in Northings. The Nukulaelae
TM Local Grid is based on the Transverse Mercator projec-
tion where the Latitude of Origin is at the equator
j
o
= 0°),
the Central Meridian
l
o
= 179° 50´ E, the False Easting = 25
km, and the False Northing = 2,000 km. The Scale Factor at
Origin is unity (
m
o
= 1.0).
On the atoll of Vaitupu, the educational center of Tuvalu, I
guess that the origin of Vaitupu Atoll Datum is at point VTZ
1 Astro: Φo = 07° 29´ 24.710˝ S, Λo = 178° 41´ 52.31˝ East of
Greenwich, and the ellipsoid of reference is the International
1924. From the Vaitupu Island Datum to the WGS84 Datum,
∆X = +193 m, ∆Y = +61 m, and ∆Z = +201 m; the accuracy of
this transformation is estimated to be ±23 m in Eastings and
±26 m in Northings. The Vaitupu TM Local Grid is based on
the Transverse Mercator projection where the Latitude of Or-
igin is at the equator (
j
o
= 0°), the Central Meridian
l
o
= 178°
41´ E, the False Easting = 10 km, and the False Northing =
1,000 km. The Scale Factor at Origin is unity (
m
o
= 1.0).
On the capital atoll of Funafuti, the coordinates of the or-
igin of the UF5 Astro Datum of 1973 are unknown but the
ellipsoid of reference is the International 1924. The vertical
datum is based on an automatic tide gauge situated on the
main jetty at Fongafale, and 48-hour readings were obtained.
The gauge is run by the University of Hawaii. From the UF5
Astro Datum of 1973 to the WGS84 Datum, ∆X = +189 m, ∆Y
= +783 m, and ∆Z = +256 m. The Funafuti TM Local Grid is
based on the Transverse Mercator projection where the Lati-
tude of Origin is at the equator (
j
o
= 0°), the Central Meridi-
an
l
o
= 179° 08´ E, the False Easting = 50 km, and the False
Northing = 9,000 km. The Scale Factor at Origin is unity (
m
o
= 1.0).
The only Micronesian community in Polynesian Tuvalu
is on Nui. Nui is 255 km northwest of Funafuti Island. On
the atoll of Nui, the coordinates of the origin of the Nui As-
tro Datum of 1965 are Φ
o
= 07° 13´ 40.09˝ S, Λ
o
= 177° 09´
47.26˝ East of Greenwich and the ellipsoid of reference is the
International 1924. The vertical datum is based on ocean
and lagoon tide levels read over four weekends. The ocean
staff gauge was off the Maneapa and the lagoon gauge was
at the Government station. The two gauges were connected
by height traverse to the local control and to the Post Office
for height of the Meteorological Service mercury barometer.
From the Nui Astro Datum of 1965 to WGS84 Datum, ∆X =
+259 m, ∆Y = +217 m, and ∆Z = –246 m. The Nui TM Local
Grid is based on the Transverse Mercator projection where
the Latitude of Origin is at the equator
j
o
= 0°), the Central
Meridian
l
o
= 177° 09´ E, the False Easting = 20 km, and
the False Northing = 4,000 km. The Scale Factor at Origin is
unity (
m
o
= 1.0).
Thanks to Jane Resture for details of local culture. Thanks
for all technical details of the complex coordinate systems of
Tuvalu go entirely to Karen French, Geodetic Branch, De-
fence Geographic Centre of the British Military Survey.
U
pdate
The Pacific Islands Geospatial and Surveying Strategy 2017-
2027 is a 10-year regional plan for developing geospatial and
surveying capacity. The Tuvalu Geodetic Survey Project
2016—Phase I was supported by Government funding and
consisted of 4 weeks for field surveys on 3 islands: Vaitupu,
Nukufetau, and Funafuti.
In 2017, completion of Phase II of the Geodetic Survey for
the four northern Islands (Nanumea, Nanumaga, Niutao and
Nui) included Geodetic survey, Cadastral survey, Topo sur-
vey, UAV/Drone survey, Tide Monitoring to establish mean
sea level or MSL, lowest astronomical tide or LAT, and high-
est astronomical tide or HAT on these 4 islands.
2018 saw completion of the last Phase III of the Geodetic
Project on Nukulaelae, Niulakita and on Funafuti again.
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).
This column was previously published in
PE&RS
.
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