An Analysis and Densification of Continuously Operating Reference Stations Cors in Nairobi and Its Environs: a Geospatial Information System Gis Approach

Abstract

Positioning and navigation has revolutionized from traditional surveying approaches, due to the significant developments in Global Navigation Satellite Systems (GNSS). The endorsement of Continuously Operational Reference Station (CORS) in Kenya has paved way for the use of Real Time Kinematic (RTK) network in provision of geospatial infrastructure for spatial data management. The spatial coverage of operational CORS within the Country as well as the Areas of Interest seems inadequate based on International Terrestrial Reference Frame standards. Consequently, the study explored existing, operational CORS as well as determining suitability of densifying them with the intent to expand their spatial coverage within Nairobi County and its environs. The study primarily employed spatial data from various sources including: Ministry of Lands; Ministry of Mining; Ministry of Transport, Infrastructure and Housing, Ministry of Environment and Natural Resources and Volunteered Geographic Information, that was manipulated using a GIS approach that is suitability analysis. Suitability analysis exploited Multi-criteria Evaluation (MCE) through defining the goal: densification of tier three CORS; determining the base criteria: Accessibility, Security, Power supply; Network density and analysis: Proximity analysis; and intersection; hence establish optimum locations/sites for establishment of CORS. The proposed CORS were subjected to another intersection in order to determine an optimum distance between the stations using Triangulation matrices of various designs: Random; East-West and North-South Triangulation Matrices, to ensure a positional accuracy of +/- 20mm is always achieved on its various applications. Consequently, IGS standards of establishing CORS stations were met through employing MCE and Triangulation Network Matrices to ensure a well-conditioned network of triangles. The approach resulted into thematic maps relaying areas with inadequate coverage, and suitable areas for CORS stations within Area of Interest.