The aim of the study is to improve approaches to monitoring and control of electronic systems of water transport, as well as navigation support itself, to improve navigation safety by developing a method for monitoring and improving the accuracy characteristics of shipboard satellite navigation equipment in real operating conditions. The article considers the importance of modern ship radio navigation systems for ensuring safety of navigation and highlights the limitations that may arise during operation of these systems. In this regard, the authors of the article propose an approach to monitoring and improving the accuracy of satellite navigation equipment of a ship in real conditions of ship operation. The article considers the use of a ground-based control and measurement station to control the precise characteristics of shipboard satellite navigation equipment. This station is installed on shore and operates based on the basic equation of metrology. The positioning system of a laser locator ship is described as follows: The GPS navigation spacecraft sends a laser beam to an optical angle reflector mounted on the vessel, and then a ground-based control and measurement station measures the time it takes for the laser beam to travel to and from the reflector, which allows the distance to the vessel to be calculated. The data is then transmitted to user equipment on the ship, which uses it in conjunction with the spacecraft's GPS navigation data to determine the ship's location, time and speed. The features of this approach are its high accuracy and applicability in various conditions, including poor visibility. To consider the geometric differences between the antennas of the ground control and measuring station and the user's equipment, as well as to consider the roll and pitch, the authors propose to use geometric ratios. The use of the method of accuracy control of shipboard satellite navigation equipment based on a ground-based control and measuring station proposed in the article allows to determine errors with high accuracy in various conditions of real operation, which contributes to the improvement of navigation safety