Global Navigation Satellite Systems (GNSS) encompass a variety of positioning systems capable of providing the necessary precision for establishing Ground Control Points (GCPs). This study delves into the impact of baseline lengths (short, medium, and long) on the positional accuracy of GNSS observable. The research involved gathering positional data from seven control stations and analyzing the effects of different baseline lengths on GNSS positioning accuracy. Satellite observations were collected at seven points within three local government areas in Oyo State (Oyo East, Atiba, and Afijo L.G.A). GNSS Receivers were utilized to collect data in static mode with 1 hour and 30-minute observation sessions at each of the seven points connected to the active CORS station. Short baselines covered distances not exceeding 5km and 56km from the test rover points to a base station within the Federal School of Surveying Oyo and a CORS located in Osun State, respectively. The medium baseline spanned distances not exceeding 103km and 153km from the test control points to CORS stations in Abeokuta and Lagos states, respectively. The long baseline extended not more than 412km from the test control points to a CORS in Abuja. An analysis of variation for all stations for each baseline was conducted. Results revealed that the precision of processing the baselines between the base stations and the rovers relies on the baseline length. The best results were attained when using long baselines of not more than 412km, as they provided better results than short baselines, although various factors can influence this.