The information provided here is as is. We try to be as accurate as we can but it is sometimes rather difficult and some projections are only approximations to enable us to have some working system.

If you have any comments on the information supplied here, please contact: webmaster@sopac.org.

SOPAC works in the range of 0 Degrees to 360 Degrees instead of the common 180 Degrees West 180 Degrees East. It means that in most case the UTM has been extended to reflect this principle. We are using Zone 31 to Zone 90 which correspond to Zone 1 to Zone 30. In this case we will note in the Projection file as following:

• UTM Zone 1(61)

Countries:

• SOPAC MapInfo?.prj
• Cook Islands
• Federated States of Micronesia
• Fiji
• Kiribati
• New Zealand
• Niue
• Samoa

SOPAC MapInfo.prj

Use the following data in your MapInfo projection file

Cook Islands

Cook Islands uses the following projection:

• Universal Transverse Mercator
• Zone 4
• Southern Hemisphere (WGS84)

Federated States of Micronesia

Maps of Pohnpei use a local grid that use neither WGS72 nor WGS84 Datum. The grid can be adjusted using an affine transformation.

X' = Ax+By+C
Y' = Dx+Ey+F

A: 1.00039582
B: 0.00002909
C: -272.99417103

D: -0.00008595
E: 1.00037993
F: -264.64201771

The affine transformation works well when converting local grid coordinates to UTM Zone 57 N WGS84 Datum coordinates. This later projection tends to be used more and more often in Pohnpei.

Fiji

The Fiji Datum is the Fiji Geodetic Datum 1986. This datum is based on the WGS72 spheroid but it is not the WGS72 datum.

A common mistake in Fiji has been to use the WGS72 Datum in place of the Fiji Geodetic Datum 1986. The Bursa Wolfe parameters were computed by the Forestry department for the purpose of the Forest Inventory Project. Forestry Department was the first department in Fiji to install a community base station (1993), therefore these parameters are widely used in Fiji. Lands and Survey has still to release the official seven parameters, which may not be anytime soon.


Fiji Geodetic Datum 1986 (from WGS84)

• Ox: -1.37101925914775"
• Oy: 0.841968640179647"
• Oz: 4.718005596536956"
• dx: 35.17277931989845m
• dy: -136.5712601696053m
• dz: 36.96429263506973m
• m: 1.537002362494988ppm

Fiji Map Grid, FMG:

• Projection: Transverse Mercator
• Datum: Fiji Geodetic Datum 1986
• Spheroid: WGS72
• Longitude: 178?45'00"E
• Latitude: 17?00'00"S
• Scale Factor: 0.9998548
• False Easting: 2,000,000
• False Northing: 4,000,000

Other datums (from Clifford J. Mugnier, cjmce@lsu.edu):

The Fiji Datum of 1956 was referenced to the International ellipsoid where the Latitude origin was obtained astronomically from station Rasusuva = 17* 49' 03.13" South, and the Longitude origin was obtained astronomically from station Suva = 178* 25' 35.835" East of Greenwich. The defining azimuth from Monavatu to Tikituru (from north) is 205* 17' 21.17". and the Transverse Mercator had a origin of the equator for latitude, Central Meridian = 178* 00' 00" East, a False Easting and False Northing of 100 Km, and a scale factor at origin of 0.9996.

The Viti Levu Datum of 1912 was referenced to the Clarke 1880 ellipsoid where the Latitude origin was obtained astronomically from station Monavatu = 17* 53' 28.285" South, and the Longitude origin was obtained astronomically from station Suva Longitude Pillar = 178* 25' 35.835" East of Greenwich. The defining azimuth from Monavatu to Tikituru (from north) is 205* 17' 21.17". The original geodetic triangulation of that island was from 1909-1912. Viti Levu island had a Cassini-Soldner? Grid with a Latitude of origin of 18* 00' 00" South, Central Meridian = 178* 00' 00" East, a False Easting of 5440 chains (68 miles), and a False Northing of 7040 chains (88 miles). (Where one meter = 0.049709782 chains.) Note that the values used for this "flavor" of Clarke 1880 ellipsoid are the same as used for the Cape Datum of South Africa where a = 20,926,202 feet = 317,063.66667 chains, and 1/f = 293.4663077.

The Vanua Levu Datum of 1915 was referenced to the Clarke 1880 ellipsoid also, where the Latitude origin was obtained astronomically from station Numuiloa = 16* 23' 28.285" South, and the Longitude origin was obtained astronomically from station Suva Longitude Pillar = 178* 25' 35.835" East of Greenwich. The defining azimuth from Naseula (East Base) to Vatia (from north) is 123* 57' 28.75". The original geodetic triangulation of Vanua Levu and Taveuni islands was from 1911-1915. The ellipsoid was naturally the Clarke 1880, and the Cassini-Soldner? Grid had a Latitude of origin of 16* 15' 00" South, Central Meridian = 179* 20' 00" East of Greenwich, a False Easting of 12513.318 chains, and a False Northing of 16628.885 chains.

The surveys were done by Captain G. T. McCaw? himself, the originator of the "War Office Spheroid" used in Ghana when he surveyed the basic network there. When he retired from the Royal Engineers, he became the originator and Chief Editor of "Empire Survey Review" journal in the United Kingdom. (Now "Survey Review.")

Kiribati

The list of MapInfo? Projection is originating from David Llewellyn who was working at the Lands and Survey department of Kiribati.

The original datum used for mapping of Tarawa was called "Secor Astro 1966". This datum utilised the International 1924 spheroid (number 4 in MapInfo). The Secor Astro 1966 datum and the associated Transverse Mercator coordinate system used has now been defined for use in MapInfo? as follows:

"Tarawa local grid (Secor Astro 1966)", 2008, 9999, 4, 259.418, -31.724, -3.795, -1.381387, -9.105050, -10.820718, 1.626, 0, 7, 173.0333333, 0, 1.0, 20000, 0, 0, 130000, 70000, 200000

Current mapping of Tarawa is based on the WGS84 datum. The coordinate system now used is the same as the above with the exception that the Transverse Mercator false easting is 40000 meters instead of 20000 meters. This is done simply to clearly distinguish coordinates that are based on the old and current systems. The new coordinate system is shown below, (WGS84 datum includes a spheroid definition and is pre-defined in MapInfo? as datum number 104):

"Tarawa local grid (WGS84)", 2008, 104, 7, 173.0333333, 0, 1.0, 40000, 0, 0, 130000, 70000, 200000


Tarawa International Datum (to WGS84):

• Ox: -1.381387"
• Oy: -9.105050"
• Oz: -10.820718"
• dx: 259.418m
• dy: -31.724m
• dz: -3.795m
• m: 1.000001326ppm

Tarawa Map Grid:

• Projection: Transverse Mercator
• Datum: Tarawa Datum
• Spheroid: WGS84
• Longitude: 173.0333333
• Latitude: 0
• Scale Factor: 1
• False Easting: 40,000
• False Northing: 0

Christmas Island 1967 (to WGS72):

• dx:+127.6m
• dy:+255.2m
• dz:-533.0m
• m:+0.219ppm

Christmas Island 1967 (to WGS84):

• ox:0
• oy:0
• oz:+0".554
• dx: +127.6m
• dy:+255.2m
• dz:-528.5m
• m:+0.219ppms

From David Llewellyn:

I took to Kiritimati a little hand-held GPS and recorded the positions standing over a few of the survey control points on the island. Using these GPS positions (WGS84 datum) and the established survey control positions (Astro67) datum I worked out the following three parameter transformation:

dx: 148 dy: 250 dz: 530

Using this, I noticed that the GPS points were still consistently shifted about 8 metres to the south of the control points. This was improved by altering the dz, thus:

dx: 148 dy: 250 dz: 538.5

I'm not sure of the reasons for this, I suspect it was because I didn't have accurate ellipsoidal heights for the points when I calculated the parameters. In any case this transformation seems to give quite a good fit between WGS84 and Astro 67.

New Zealand

Nautical charts in New Zealand uses the New Zealand Geodetic Datum of 1949.

Niue

Niue is using the Niue Gedodetic Datum of 1991 which is based on the GRS80 Datum. The use of one or the other is equivalent. The Niue Map Grid is based on the location of the reference mark "Tomb Point" which has had its coordinates computed with the Niue Geodetic Datum 1991.


Niue Map Grid, NMG:

• Projection: Transverse Mercator
• Datum: Niue Geodetic Datum 1991 / GRS80
• Spheroid: GRS80
• Longitude: 190.07912467 (-169.92087533)
• Latitude: -19.053878
• Scale Factor: 1
• False Easting: 5,000
• False Northing: 15,000

Samoa

Samoa uses the Western Samoa Integrated Grid, WSIG, which was adopted in 1988. The grid is based on the WGS72 Datum.


Western Samoa Integrated Grid, WSIG:

• Projection: Transverse Mercator
• Datum: WGS72
• Spheroid: WGS72
• Longitude: 188 (-172)
• Latitude: 0
• Scale Factor: 1
• False Easting: 700,000
• False Northing: 7,000,000