A country's network of Continuously Operating Reference Stations (CORS) delivers real-time, precise three-dimensional positioning. A CORS network is a collection of Global Navigation Satellite System (GNSS) receivers strategically placed throughout a region as part of the country's geodetic infrastructure. CORS networks can also be used to track and record the movement of the continent, allowing the reference frame and datum for geoscience and spatial datasets to be developed, enhanced, and maintained (ICSM, 2014).
The CORS approach began in early 1990 when National Geodetic Survey (NGS) installed the initial permanent GPS receiver in the Gaitterburg Campus in the USA and culminated in more installations in Maryland, Colorado, and other networks that formed part of the Cooperative International GPS (CIGNET) network. In early 2000, more stations had been installed, raising the number to almost 200 stations, steadily increasing to 1400 as of 2014, and thus adopted as the primary geodetic spatial data infrastructure (Kusimba, 2018).
In Africa, some countries installed CORS with the initiation of the African Geodetic Reference Frame (AFREF) has triggered a group adoption, i.e., Kenya, Nigeria, South Africa, Benin, and others. As a result of its geodetic accuracy, it is more attractive to invest in such a venture. The goal of AFREF is to promote the adoption of modernized geodetic reference in Africa as well as its unification, that is, a seamless reference ensuring uniformity. Therefore, it ensures the nations within the African continent implement the aforementioned modernized GNSS technologies, hence the establishment of the CORS network that will support various activities affiliated with mapping such as cadastral surveys, engineering survey, and geodynamics (Combrinck, 2010).
In Ethiopia, the first CORS was created in 2007 as part of the international GNSS service (IGS) stationed by the Institute of Geophysics, Space Science, and Astronomy (IGSSA) at Addis Ababa University's Arat Kilo Campus. In 2015, the TANA IGS station was built by the Institute of Land Administration (ILA) at Bahir Dar University. The Ethiopian Geospatial Information Institute (GII) is in charge of establishing the CORS network for geodetic applications across the country. As part of this endeavour, GII collaborated with assistance organizations to create four CORS in Ethiopia: Gondar, Jimma, Dire Dawa, and Addis Ababa. However, the number of CORS already in place does not cover the entire country of Ethiopia. Despite the fact that various research on CORS network architecture have been undertaken around the world and in Africa, there are no comprehensive and substantial studies in Ethiopia. Without a suitable design and installation of the CORS network in Ethiopia, it will be difficult to support the ever-growing geospatial applications.
"To construct the geodetic network, it is important to plan the network beforehand," as Alizadeh-Khameneh (2015) shown. As a result, the goal of this research is to create a CORS network that encompasses Ethiopia. The availability of the mobile network, accessibility, and network geometry should all be considered during the design phase. It also includes a network observation plan as well as some measurement performance recommendations. The ultimate goal of network design is to create a network that is optimal in terms of precision, dependability, and cost. The correctness of the planned network will be verified using virtual reference station principles (VRS).