3.4.5.2. Disadvantages

• A good visibility for the sky is necessary, as high rise buildings obstruct the signals.

For GNSS to work effectively, the receiver must have a clear view of the sky. Tall buildings, trees, and other obstacles can block the signals from the satellites, leading to a poor signal quality or no signal at all. Without direct line-of-sight to the satellites, the receiver cannot accurately determine its position.

Imagine trying to call a friend on your phone while you're inside a concrete building. You might not be able to hear them because the walls block the signal. Similarly, GNSS receivers struggle to find their location if they are surrounded by tall structures.

• It can’t be used for indoor positioning.

GNSS systems rely on signals from satellites that are typically located far above the Earth. When these signals enter buildings, they can become too weak or distorted to be useful for positioning. As a result, GNSS is not effective for indoor navigation or location tracking.

Think of GNSS like using a flashlight in a dark room. If there are no barriers, the light shines bright, illuminating your path. However, if you close the door and turn off the light, you can't see anything. Similarly, without the direct signals from satellites, GNSS can't give accurate positions indoors.

• It can’t give precise results in areas like forest, under a bridge, tunnel, etc.

GNSS signals can become distorted or blocked in dense environments such as forests, where trees can obstruct signals, or in tunnels and under bridges, where the signals cannot reach the receiver at all. These limitations can lead to significant inaccuracies in position determination.

Imagine trying to watch a movie on your phone in a crowded theater. With everyone around you and the sound playing loudly, you might miss some of the important dialogues. Similarly, in a densely wooded area, the satellites’ signals can be blocked and lead to poor positioning.

• Vertical precision is not enough for some applications.

While GNSS systems can provide horizontal positional accuracy, their vertical precision is often less reliable. This means that for applications that require precise altitude information (like aviation), the GNSS data may not be sufficient.

Consider a builder working on a tall skyscraper. They need exact measurements of how high each floor should be. If the measuring tool (like a GNSS receiver) can only give rough estimates, they might end up with uneven floors. Accuracy is vital, especially in critical applications.

• Extreme atmospheric conditions, storms can contribute to errors in GPS observations.

Weather can greatly affect GNSS accuracy. Atmospheric conditions, such as storms or high levels of humidity, can cause delays in the signals traveling from the satellites to the receiver. These delays can introduce errors in the calculated position.

Think about how difficult it is to play a game that requires quick responses, like driving a fast go-kart, in heavy rain. You might not be able to see the track clearly and could misjudge your steering. Similarly, atmospheric conditions can prevent GNSS from providing the accurate positioning needed.

• With limited number of satellites, accurate results may not be obtained.

GNSS accuracy is directly related to the number of satellites visible to the receiver. If there are not enough satellites in view, the receiver may struggle to provide an accurate position. Ideally, a minimum of four satellites is needed for a reliable three-dimensional position fix.

Imagine you're trying to solve a puzzle but you only have a few of the pieces. Without enough pieces, the full picture remains unclear. Similarly, without a sufficient number of satellite signals, the GNSS receiver cannot fully determine your location.

--