Closest Point of Approach.

It’s one of the key safety features you get when your Simrad GO9 receives AIS data (from an RS40 or RS40-B).

✅ What CPA Actually Means

CPA tells you how close another vessel will come to you if both of you continue on your current course and speed.

Example:

A ship is 2 miles away
Your GO9 shows CPA 0.25 NM
That means the ship will pass within a quarter mile of you
Your GO9 will also show TCPA (Time to CPA) – how long until that happens

👍 Why CPA matters

CPA helps you quickly determine if another vessel is a collision risk.

High CPA (1 NM, 2 NM, 5 NM)
→ Safe. No action needed.
Low CPA (0.1 NM, 0.2 NM)
→ Possible collision or very close pass.
TCPA (Time to CPA) tells you how soon that close approach will happen.

Your Simrad can also alarm:

CPA alarm – “Hey, this guy is going to get too close to you.”
TCPA alarm – “He will get close in X minutes.”

This is extremely useful in:

Fog
Night
Busy ICW channels
Offshore with big fast ships
When someone is on a collision course but you don’t notice it visually

🚤 What you need for CPA to work

You need AIS data on your GO9:

RS40 → AIS receiver → you see their position, speed, CPA
RS40-B → AIS transceiver → you see them & they see you
RS20S → No AIS → no CPA information

📌 Simple definition

CPA = The closest distance another boat will come to you if neither of you change course or speed.