How to Use Radar in Low-Visibility Conditions

Stay safe and stay aware—when sight fails, your radar becomes your best friend.

Fog, darkness, rain—every boater faces times when visibility drops and decision-making becomes more stressful. That's when marine radar steps in as a vital tool, helping you see what your eyes can’t.

Whether you're navigating a narrow inlet in the dark or cruising offshore in thick fog, here’s how to use your radar effectively in low-visibility conditions.

Step 1: Know Your Radar’s Basics

Before you're in a low-vis situation, get familiar with your radar system. Modern radars from Garmin, Simrad, Raymarine, and Furuno often include features like:

Automatic Gain & Sea Clutter Adjustment

MARPA (Mini-Automatic Radar Plotting Aid) for tracking targets

Guard Zones to alert you of nearby objects

Overlay on chartplotter or MFD for better context

Step 2: Set Up for Fog, Rain, or Night

Radar performs best with the right settings:

Use Harbor or Coastal Mode

These modes prioritize close-range resolution, ideal for navigating in tighter areas or harbors.

Adjust Gain, Sea, and Rain Clutter

Gain controls sensitivity. Too high and you'll see noise, too low and you'll miss targets.

Sea clutter reduces echoes from wave tops.

Rain clutter filters out precipitation noise.

Tip: Start with Auto modes, then fine-tune manually if needed.

Use Range Rings

Set range rings (e.g., 1/2 nm or 1 nm spacing) to judge distances quickly from your position.

Step 3: Interpret the Screen Like a Pro

Understanding what you're seeing is crucial:

Strong echoes = solid objects (boats, land, buoys)

Weaker echoes = smaller objects or distant targets

Dead zones can occur directly behind tall structures on your boat (like masts)

Practice spotting: Channel markers, Headlands, Passing vessels

Step 4: Combine Radar With Other Tools

Radar works best when combined with other sensors:

AIS: Shows nearby vessels broadcasting position, course, and speed

GPS/Chartplotter: Use radar overlay to align radar data with your navigation chart

Sound signals: Always follow COLREGS in fog—use horn and listen for others

 

When the horizon disappears, radar is your second set of eyes. With practice and the right settings, radar becomes a powerful tool for safe navigation in fog, rain, or night.

If your current system doesn’t include radar—or if you're using older tech—it might be time to upgrade. Contact Marine Electronic Pros and we’ll help you choose and configure the right radar system for your needs.