Why Does AIS Signal Delay Happen on Marine Radar?
Many users wonder why a vessel doesn’t always work exactly where they expect it to be. You’re not alone if you’ve ever opened a marine radar app and seen that a ship’s position appears to be a little out of date. This situation is commonly known as an AIS signal delay, and in most cases, it’s completely normal.
To understand why the delay happens, it helps to know how AIS works in real-world settings, on the open sea. Let’s learn more about it from this blog.
What Is an AIS Signal Delay?
An AIS signal delay happens when there is a time gap between when a ship sends its location and when that information appears on your screen. In simple terms, the vessel has moved, but the latest update hasn’t yet reached the marine radar system.
This doesn’t mean the vessel is lost or that the app is broken. Instead, it usually means the system is waiting for the subsequent AIS transmission.
How Does AIS Work Behind the Scenes?
AIS, or Automatic Identification System, is like a digital ID card for ships. Each vessel sends out radio signals that include details such as
- Current location
- Speed
- Direction
- Vessel type
- Identification number
These signals are sent using VHF radio waves. However, they are not sent continuously. Instead, ships transmit data at different intervals depending on their speed.
What are the common reasons for AIS signal delay?
There are several reasons why an AIS signal delay can occur.
1. Vessel Speed and Movement
First of all, AIS update frequency depends on speed. Ships moving slowly or at anchor may transmit data only every few minutes. As a result, their positions may appear delayed on the map.
2. Distance from the Coast
AIS signals are detected by land-based receivers close to the coast. However, in the open ocean, satellites collect data. Since satellites don’t provide constant coverage everywhere, delays can happen more often offshore.
3. Satellite Refresh Timing
Even when satellites receive AIS signals, the data still needs to be processed and forwarded. Therefore, a short delay between transmission and display is normal, especially in busy shipping areas.
4. Weather and Sea Conditions
Although AIS is reliable, heavy rain, storms, or rough seas can interfere with radio signals. As a result, updates may arrive more slowly than usual.
5. Onboard Equipment Limitations
Sometimes, the issue comes from the vessel itself. Outdated AIS equipment or temporary technical issues may reduce signal frequency.
How does the MarineRadar app handle AIS delays?
The MarineRadar app doesn’t simply remove a ship when updates slow down. Instead, it displays the last known position along with a timestamp. This helps users understand how fresh the data is.
In many cases, the app may also estimate the vessel’s movement based on its last recorded speed and direction. That way, you still get a helpful picture of where the ship might be.
When Should You Be Concerned?
Most AIS delays are harmless. However, there are situations where you should pay closer attention.
For example:
- If a ship near the coast hasn’t updated for many hours
- If the “last seen” time keeps increasing without any new data
- If speed and direction stop changing completely
In these cases, the vessel may have turned off AIS or moved into a signal blind zone.
How Can Ship Tracking Be More Accurate?
Once you know what to look for, AIS data becomes much easier to interpret.
To get the most accurate view:
- Always check the “last updated” or “last seen” time
- Watch the vessel for a few minutes rather than relying on a single snapshot.
- Understand that delays are part of global ship tracking.
Conclusion
An AIS signal delay is a natural part of maritime tracking. Ships, satellites, weather, and distance all play a role in how quickly data reaches your screen.
You can use marine radar tools with confidence if you are aware of these factors. Even delayed data can still provide important information about vessel movements worldwide.
Download Marine Radar: Vessel Tracker from the Google Play Store or App Store today and experience real-time ship tracking.
