88
February 2019
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
ic mapping was compiled in the 1960s by the British Direc-
torate of Military Surveys, and a 1:50,000 scale map series
(K763) comprising 155 sheets was completed in 1969.
Limited 1:50,000 mapping was produced in the early 1980s
with the assistance of Syria, but coverage of Dubai was based
on only four third-order points in the southeast corner of the
Emirate. A military survey department was set up by the
Emirates and new mapping was published between 1989
and 1991 as 138 orthophoto sheets on the Nahrwan Datum
of 1929 with the UTM Grid. A new GPS network was ini-
tiated for Dubai in 1991 with a new local Grid. The Dubai
Local Transverse Mercator (DLTM) Grid is referenced to the
WGS 84 ellipsoid, the Central Meridian
l
o
= +55° 20’ E, and
the False Easting = 500 km. The Northings are presumably
measured from the Equator. Analysis of the old network in-
dicated a potential positional error of the old classical control
of up to 9 meters horizontal. The First Order Geodetic GPS
Network of Dubai is composed of 62 monumented points with
distances between points ranging from 5 to 10 km. Of par-
ticular interest is that Dubai has completely abandoned the
previous classical geodetic work extant in the Emirate. Zero
effort was (apparently) made to relate the old to the new! I
personally do not agree with this philosophy because I prefer
to relate historical records to current and future work. How-
ever, I suspect that this unfortunate tack may be chosen from
time-to-time for the sake of expediency.
Satellite positioning studies (by others) in the United
Arab Emirates derived a set of Datum shift parameters from
WGS72 Datum to Nahrwan Datum of 1929 where:
D
X =
+225.4 m,
D
Y = +158.7 m,
D
Z = +378.9 m, based on observa-
tions of 8 stations. I personally would consider the tenths of a
meter used in these parameters as very optimistic. Interest-
ingly, NIMA lists the transformation from Nahrwan 1929 to
WGS 84 as
D
X = –249 m,
D
Y = –156 m,
D
Z = –381 m, ±25 m,
based on two stations observed in 1987.
U
pdate
Significant developments have been implemented in the coor-
dinate reference systems for two primary areas of the United
Arab Emirates: in Al Ain Region, Abu Dhabi and in Dubai. In
Al Ain Municipality, Professor Kamal A. Abdalla of the Univer-
sity of Khartoum, Sudan spent a number of years as a consul-
tant to the region, and in 2005 published a paper that stated,
“The local geodetic network adopt(ed) Ras Ghantut
datum and (is) based on the modified Clarke 1880
ellipsoid. The local control stations are non-homoge-
neous, unadjusted and have many limitations in terms
of spatial data applications. While the global geodet-
ic network is tied to the ITRF system, containing 33
well-distributed geodetic control stations. The transfor-
mation parameters between the global datum and the
local datum were computed.”
1
In the Dubai Municipality Survey Department,
2
a Leica
SmartNet™ has been established in order to provide a virtu-
al reference system (VRS) to the emirate.
3
Furthermore, the
paper,
An Absolute/Relative Gravity Base Net in the Emirate
of Dubai
,
4
details a new fundamental gravity network of nine
relative and absolute gravity stations and that “These mea-
surements were the first absolute gravity determinations in
the whole South-West Asia.”
1 Al Ain Local and Global Spatial Reference Systems, Map
Middle East 2005.
2
3 Al Marzooqi, Y., H. Fashir, T. Babiker.
Establishment
& Testing of Dubai Virtual Reference System (DVRS)
National GPS-RTK Network
. 2009. Geospatial Word.
ing-of-dubai-virtual-reference-system-dvrs-nation-
al-gps-rtk-network/. Accessed 11 January 2019.
4
, Accessed
11 January 2019.
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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