Iraqi Geospatial Reference System

by Wisam Al Hassani

Geodetic and mapping work in Iraq goes back at least a century. The Surveying and Mapping Directorate where I work was established by the British after they occupied Iraq in 1921. They also built Iraq’s first-order horizontal and vertical networks and produced the first national map for Iraq. We still use that map to determine property ownership. The vertical datum, which we call the British Vertical System, it(GTS), has its starting point in Mean Sea Level (MSL) on the Persian Gulf; benchmarks were established by conventional leveling. Older irrigation projects are based on that datum.
In 1974, intent on modernizing surveying and mapping activities in Iraq, the government signed a contract with a Polish company. The objective was to establish new horizontal and vertical networks in Iraq and redraw the country’s map using aerial photogrammetry.
Under the contract, Iraqi geodesists triangulated 2600 horizontal points between 1974 and 1979. The points were distributed in 15-km intervals, and they were determined by astronomic observation, triangulation, trilateration, and least squares adjustment.
At that time, this network was one of the best in the region. There is little information about it in literature, but we know that its reference frame was the Clarke 1880 spheroid, because it had the best non-geocentric fit for Iraq.
For the vertical network, also known as the National Elevation Network, 1600 first-order vertical benchmarks were levelled from the MSL measured in Fao city on the Persian Gulf. Gravimetric measurements were also taken using conventional geodetic precise leveling to distribute the network along the main roads with a spacing of about 5 km. Information about the calculation of this national elevation datum is incomplete, and because of this, some of our irrigation projects still use the British vertical datum.
Between 1980 and 2003, surveying and mapping activities in Iraq were relegated to the back burner, because of civil strife and war, but also due to restrictions placed by the old regime on the use of GPS to measure coordinates for mapping. The combined effect of misguided policy and instability in Iraq in recent years was the loss of about 60 percent of our horizontal and vertical networks.
After 2003, the General Directorate for Surveying and Mapping started from zero—just like many other government agencies. They were helped by surveyors and mappers serving in the coalition forces and by experts from other countries.
In 2005, the U.S. and British army started a project whose goal was to develop a new geospatial reference system in Iraq, the IGRS. Several agencies were involved, especially, on the U.S. side, the National Geodetic Survey and the National Geospatial-Intelligence Agency (NGA).
Six CORS (continuously operating reference stations) were initially installed in Iraq (see map) as part of the project. To supplement the CORS data, 64 HARN (Height Accuracy Reference Network) points were levelled in four provinces in southern Iraq. Heights were determined using the ITRF00 datum, togeter with the GRS80 spheroid and EGM96 (Earth Gravity Model 1996). The Iraqi engineers working on this project used the OPUS service on NGS’s web site to process HARN data.
In 2006, NGS invited six engineers from the Ministry of Water Resource to attend a 20-day workshop on issues relevant to the IGRS project, such as datum definition, datum transformation, geoid modeling, GPS processing, tidal and geodetic vertical datums, RTK development, CORS installation, and site management.
The workshop gave impetus to efforts to complete the IGRS project begun in 2005. On our return to Iraq, we developed a proposal, in consultation with the Ministry of Water Resource, the U.S. Embassy in Baghdad, and the U.S. Army 20th Engineer Company in Iraq, which puts Iraqi surveyors and mappers in charge of the Iraqi Geospatial Reference System. The proposal, which benefited from insights by NGS’ Dave Doyle, identifies six goals for our future work.

Install more CORS
The CORS set up in Iraq in 2005 were located at U.S. and British military camps. The original plan was to transfer those stations to our Ministry, but operations at the stations were stopped in February 2007 because of a problem the central computer in Baghdad experienced after the installation of the DOD firewall.
The U.S. Army is working to solve this problem. However, because of the urgency to complete the IRRS, seven new CORS were provided as a gift to our country through the U.S. Embassy in Baghdad. These stations will be operated under Iraqi jurisdiction. We decided to install the first that has arrived on the premises of the Ministry of Water Resources, in the proximity of the central computer. The U.S. Army engineers will help with the installation, and NGS will connect the station via a link to the NGS web site, to enable us process the data in OPUS. The remaining six stations are due to arrive early in 2008; they will be distributed throughout Iraq so as to get the best coverage possible. The Bagdad CORS station will be incorporated into the IGRS in the near future.
Develop a datum transformation program
One of our most urgent goals for the IGRS is to develop a program that will enable transformations between the old Polish datum (Clarke 1880 spheroid) and the new ITRF00 (GRS80 spheroid) datum. GPS observations on the Polish horizontal first-order network are needed to calculate the difference between the two datums. NGS is helping us to adapt NADCON—a program used to transform from NAD 27 to NAD 83—to Iraq’s needs. Engineers from the Surveying and Mapping Directorate are working together with NGS to collect GPS data.

Develop a high-resolution GEOID model
Iraq urgently needs a high resolution geoid. To calculate the geoid, we need to determine the GPS height differences between the Polish MSL datum and the GRS 80 ellipsoid and combine these values with absolute gravity data. We’re in the process of collecting the data, with NGS’s assistance. NGA is working on the EGM07 model, which is scheduled for release in early 2008. NGA’s Dr. Steve Kenyon will help us populate the model with the GPS data we are collecting so as to achieve the best fit for Iraq.

Install High Accuracy Reference Network (HARN)
Work is in progress to install HARN points in other provinces, to complement those installed in southern Iraq. The entire country should be covered in two years. The maximum distance between the points is 15 km, as per NGS specifications, and the frequency of GPS observations is 5.5 hours with two sessions. The points’ orthometric height was found using conventional double precise levels. The nearest Polish first-order vertical network benchmark was the reference; these benchmarks may or may not be error free, given that no information exists on the movement of the Iraq plate since 1978 GPS data were processed in OPUS and integrated in the geodetic reference system. The results were compared with GPS data published on AUSPOS, a Geosciences Australia web site.

Build a GEODATA database
One of the important goals in this project is to build a digital data base which will include digitized versions of the old horizontal and vertical datums, as well as the new datum, the IRGS. In 2005, the U.S Army survey team created an interactive CD containing data and other information pertinent to their work they. We decided to keep updating this “databse” with data from our work, such as the new HARN points levelled in the provinces. In addition, we’re developing a GEODATA database for the IRGS project, using ARC GIS 9.1 software to capture the old horizontal and vertical datum data as well as the newly collected CORS and HARN data.

Publish IGRS
When completed, the Iraqi Geospatial Reference System will be the new official reference system in Iraq, providing surveying companies with an accurate horizontal datum, a geoid, and a datum transformation program to enhance their work. Users will be trained to use the IGRS, and workshops to acquaint other ministries in Iraq with the system and its capabilities are planned. There will also be workshops intended to teach surveyors how to apply GPS techniques.

Develop a National Water Level Program
This will necessitate designing and install ing state-of-the-art, long-term water level stations at four key locations and tying in the water-level-derived datums to the geodetic reference system. The four stations will be established at Al Faw, Abadan, Al Basrah, and Um Qsar. This work is part of our future goals, because we need more experience and would therefore need to establish cooperative ties with other Iraqi and international agencies.

Acknowledgements
All surveyors currently working on the IRGS project, despite the difficult security situation, are to be congratulated for their dedication. In particular, we are indebted to the MNC-I C7 Geospatial NCO U.S. Army survey team in Bagdad, Dave Doyle of NGS, Dr. Linda Allen and Dr. Maged Hussein of the U.S. Embassy in Bagdad, and NGA’s Dr. Steven Kenyon.

For more information on the work described in this article, contact Eng. Wisam Hussein at:
Wisamalhassani2000@yahoo.com or Wisamalhassani2000@hotmail.com