Challenge

Following the United Nations resolution to adopt a global geodetic reference network, the Government of Uganda, with assistance from the World Bank, commissioned Fugro and its joint venture partner IGNFI to design and implement a modern, reliable and accurate geodetic reference frame (GRF) over an 18 month-period and in challenging topographical conditions.

Spanning the entire country, the frame supports land administration, physical planning, land development, construction, environment protection and other spatial data activities.

The frame included:

• 12 continuously operating reference stations (CORSs)

• 129 first-order geodetic markers homogeneously distributed across the territory

• 297 second-order geodetic markers to densify the coverage in urban and developing areas

Our work also included computations of geodetic transformations to historical datums, an interim geoid model and training of the Ugandan survey community throughout the project.

Solution

Working with our IGNFI joint-venture partner, we implemented the project in four phases:

1. Network design (3 field months): a field reconnaissance of the existing trigonometry points and levelling benchmarks, and a countrywide search for sites for the new geodetic points. The reconnaissance involved three local teams, supervised by a Fugro Project Manager

2. Monumentation of 426 geodetic markers (6 field months): a Fugro Project Manager supervised nine local technical teams and four sociologists, who managed relationships with local people

3. GNSS observations on 426 new points and 60 existing points (50 field days): 13 local teams carried out global navigation satellite system (GNSS) observations of 993 baselines. Two Fugro party chiefs were onsite to supervise the teams and post-process the observations to validate the GNSS data and update the measurement programme

4. Computation and adjustment (3 months): we implemented a dual-processing strategy that relied on scientific software to ensure accuracy and integrity of the new coordinates, including computing the first- and second-order networks using the imbricated orders method, and using 20 trigonometry points to derive all possible types of geodetic transformations between reference and historical geodetic datums

Innovative highlight

As part of this GRF project, we implemented a new method of collecting digital field observation sheets to gather all required metadata. The digital field observation sheets improved the office team’s management of quality assurance and quality control while the work was being carried out by the field teams. This new approach ensured full compliance with procedures and project requirements.

Impact

We provided a long-term, homogeneous, accurate and easy-to-use solution that benefits the entire Ugandan survey community. This new infrastructure allows local survey practitioners to perform complementary surveying work without the need for local adjustments. This approach is designed to maintain a high level of consistency in planimetry and height for all future projects, such as cadastral surveys, city developments and road construction.

Our experts delivered training at different stages of the project to help the survey community derive maximum benefit from our work and increase their knowledge about the different products delivered.