The Position Calculation and Satellite Selection sections are a little over-simplified. It's not true that one satellite is used for time synchronization and three are used for trilateration. In a four-satellite case, all four are used to solve the four dimensional problem of "where am I in time and space?" In reality, upwards of 12 satellites are used to find a solution to this problem and adding more data improves accuracy.
It's true that satellites overhead provide better more vertical position information and that satellites at low elevation are more impacted by the atmosphere. But the math isn't that simple - satellites aren't used for specific purposes. They all contribute to a position solution and useful parameters like vertical and horizontal uncertainty.
It's true that satellites overhead provide better more vertical position information and that satellites at low elevation are more impacted by the atmosphere. But the math isn't that simple - satellites aren't used for specific purposes. They all contribute to a position solution and useful parameters like vertical and horizontal uncertainty.