PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
February 2018
63
Clarke 1880 (modified) ellipsoid where a = 6,378,249.145 me-
ters, and
1
/
f
= 293.465. The False Easting was changed to
274,319.736 m. In 1991, the National Imagery and Mapping
Agency (NIMA) published the three-parameter datum shift
values from Leigon Datum of 1978 to WGS 84 based on eight
collocated points where:
Δ
X = –130 m. ± 2 m.,
Δ
Y = +29 m. ±
3 m.,
Δ
Z = +364 m. ± 2 m. Out of curiosity, I decided to try
an 8-point solution for a 7-parameter Bursa-Wolf shift from
Leigon Datum of 1977 to WGS 84 Datum. The resultant was
Δ
X = –110.90 meters,
Δ
Y = –9.13 meters,
Δ
Z = +69.46 meters,
Scale = +3.11 X 10
6
, R
x
= –1.30 arc seconds, R
y
= +9.53 arc
seconds, and R
z
= +0.32 arc seconds. The in-crease in good-
ness of fit was about ten-fold over the 3-parameter solution.
An example data point is station (G.C.S. T20/24) “Wa” on the
Leigon Datum of 1977 where:
f
= 10
o
02´ 47.7770˝ North, and
l
= –2
o
28´ 17.3746˝ West, and a MSL elevation of 359.7 me-
ters with coordinates of “Wa” on the WGS 84 Datum where:
j
= 10
o
02´ 56.3328˝ North, and
l
= –2
o
28´ 16.6377˝ West and
an ellipsoid height of 385.1 meters. Of course, on the WGS 84
Datum the coordinates are expressed on the UTM Grid, and
not on Colony Coordinates.
U
pdate
Ghana has installed a new GPS network of Continuously
Operating Reference Stations (Poku-Gyamfi, Y., & Schueler,
T.,
Renewal of Ghana’s Geodetic Reference Network
,
LNEC
,
Lisbon 2008). Numerous publications have been devoted
to an exploration of various math models for modeling the
transformation parameters from Accra Datum of 1929 and
Leigon Datum of 1977 to WGS84 Datum: (Poku-Gyamfi, Y., &
Hein, G.,
Framework for the Establishment of a Naitonwide
Network of Global Navigation Satellite System
,
5
th
FIG
Conference
, Ghana, 2006), (Dzidefo, A.,
Determination
of Transformation Parameters between the World
Geodetic System 1984 and the Ghana Geodetic Network
.
Master’s Thesis, Department of Civil and Geomatic
Engineering, Kwame Nkrumah University of Science
and Technology
, Ghana, 2011), and Ziggah, Y.Y.,
et al
,
(
Novel Approach to improve Geocentric Translation Model
Performance Using Artificial Neural Network Technology
,
Boletim de Ciências Geodésicas
– On-Line Version, ISSN
1982-2170, 2017). Work and analyses appears to be primarily
in the “Golden Triangle Region” of Ghana.
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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