Abu Dhabi Survey Coordinate System and Datum

The standard states that UTM projection is used in the Emirate of Abu Dhabi based on the WGS84 ellipsoid at ITRF 2000, epoch 2000.0. Two zones cover the emirate: Zone 39N and Zone 40N, in metres, carrying EPSG codes 32639 and 32640. The ellipsoid parameters are given explicitly, with a semi-major axis of 6378137.000 m and a semi-minor axis of 6356752.31424 m.

The epoch is the part that is read past most often. WGS84 at ITRF 2000, epoch 2000.0 is a specific realisation at a specific date, not a loose synonym for “GPS coordinates”. A receiver delivering positions in a current realisation is not automatically delivering them in the one the standard names, and on a large site the difference is not negligible.

Which of the two zones applies is a function of where the project sits, and a site near the zone boundary needs that answered explicitly rather than assumed from whichever zone the last project used.

The standard names Ras Ghumays as the official vertical reference for Abu Dhabi Emirate, based on mean sea level observations. It goes further than naming it: it requires that all mapping, planning, design and construction for each new, modified or improved infrastructure project within the municipal and transport sector of the emirate be based on it.

Levels are where a reference error does the most damage, because a vertical offset is uniform, invisible in plan, and survives every downstream check that compares one drawing against another. It shows up against a kerb, an invert or a tie-in — by which point the design has been built around it.

Control is established once, at the start, and everything measured afterwards inherits it. A point cloud, an as-built drawing and a BIM model produced from the same survey all carry the same reference, correct or otherwise, and correcting it later means transforming every one of them and re-checking the result.

The reference also travels into the submission. The geodatabase templates published with the standard carry a predefined coordinate system, so data referenced to something else does not merely look different — it does not load into the template as delivered.

The most common and most expensive assumption is that a UAE project inherits a single national convention. It does not. Each emirate sets its own requirements for work delivered to its own authorities, and a team that has only worked in one of them has no reason to have discovered that.

A related one is treating the vertical datum as a detail to be resolved during processing. It is a mobilisation decision: it determines which benchmarks the levelling is tied into, and benchmarks are chosen on site, not in the office afterwards.

On terminology, one point is worth stating because it circulates: the Department of Municipalities and Transport standard itself specifies the references set out above. Those are the names to use in a scope, a method statement or a deliverable schedule, because they are the ones the governing document uses.

• Surveying in Abu Dhabi →