- SPECIAL REPORTS
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Located along the Gulf of Guinea in West Africa, the Republic of Benin has a land area of 42,500 square miles--slightly smaller than Pennsylvania. Since the early 1990s, Benin has been actively working to improve the standard of living for its citizens through sustainable economic development. In spite of its efforts, Benin’s per capita income remains below average for sub-Saharan Africa. Thirty percent of its approximately 8.5 million inhabitants live in poverty, and rural poverty continues to increase. It’s a challenging situation.
Barthel says that the situation in urban areas is similar. Residents have habitation permits that allow them to occupy a parcel, but they lack legal title to the land. For Benin and other developing countries, establishing a sustainable land registration and cadastral foundation is critical.
To accomplish these objectives, Benin first needed to establish a national geodetic reference framework.
Again with technical guidance from NGS, IGN developed a standard design for the CORS installations. The design for the monument structures that support the antennas was based on older conventional geodetic monuments in Benin and modified to handle the strict requirements for stability and data integrity. Each CORS site included a small building to house the receiver, power supply, communications and other equipment.
IGN selected Trimble NetR5 Reference Station receivers and Trimble Zephyr Geodetic 2 GNSS antennas for the CORS locations. For the station in Cotonou, they installed a Trimble GNSS Choke Ring antenna to reduce the effects of multipath. The Trimble NetR5 tracks both GPS and Glonass satellites, including the GPS L2C and L5 signals, and will therefore allow the Benin CORS to deliver high-level performance for many years to come.
The seven CORS are managed by a control center in Cotonou running Trimble GPSNet Software. The CORS stream raw data to the control center for use in post processing. Communications links to the rural areas are limited. Some of the CORS have DSL connections, while more-remote sites rely on VSAT (satellite phone) connections.
With training and support from Trimble along with assistance from NGS and the University Navstar Consortium (UNAVCO), a nonprofit organization facilitating geoscience research and education using geodesy, IGN completed the work of installing and establishing coordinates on the CORS. The first CORS came online in 2008, and the entire system was completed and operational in May 2009. The station in Cotonou is part of the African Geodetic Reference Frame (AFREF) project and also operates as part of the NGS CORS system.
The Access to Land Project includes the creation of Rural Landholding Plans (Plans Fonciers Ruraux, or PFR) to collect and manage Benin’s rural land information. The PFR called for mapping existing parcels to an accuracy of 20 to 30 centimeters (0.6 to 1.0 feet). For this work, MCA-Benin and IGN selected Trimble GeoXH hand-held receivers with external antennas and Trimble TerraSync field software. In May 2009, a group of 50 contracted surveyors received training on the Trimble GeoXH system, including field operations, post processing and GNSS concepts. “They have excellent knowledge of surveying and geodesy. “They just lacked access to the current technologies,” Barthel says of the team members. “And now the new equipment is solving that.”
To achieve the needed accuracy in the rural areas, the contracted surveyors use Trimble H-Star technology and post process the rover data with data from the CORS. All post processing is done using Trimble GPS Pathfinder Office software. The software automatically downloads data from the nearest CORS and computes coordinates based on Benin’s national grid. After the data are checked and analyzed by IGN, the results are loaded into land information systems running under ESRI ArcGIS.
For the survey control work, IGN selected Trimble R8 GNSS receivers and Trimble TSC2 Controllers running Trimble Survey Controller software. The teams use static methods to establish local control points referenced to the national CORS network and process the GNSS data using Trimble Business Center software. They can then use the local control points as RTK base stations.
Benin’s decision to leapfrog the technology curve is paying off. When the MCC-funded work is completed, roughly 30,000 occupancy permits in urban areas will convert to land titles and 85,000 households in rural areas will receive titles or certificates. As the residents gain legal title to their land, private sector investment and activity is expected to increase, Barthel says. And as Benin’s communication infrastructure improves, the surveying and mapping work will move ahead. Future enhancements include providing real-time DGPS and, possibly, RTK correction services. It’s a big step for a small country.
* The views expressed in this article are solely those of the individual quoted and do not necessarily represent the views of the Millennium Challenge Corp. or the government of the United States.