The best tool for both fog and measuring distance is radar. If I had a forced choice between a chartplotter and radar, I would choose radar.
I have used radar to anchor in fog. I just pick a spot with sufficient distance to the other vessels. Very slick.
When underway in restricted visibility radar will pick up other vessels and objects, a chartplotter will not.
Totally agree. Radar would have shown the ship that almost ran us down one dark night going out the San Francisco ship channel. Our boat, shown below, had only a compass & a radio direction finder.
It was our perception that radar was "too expensive", which was wrong.
"How much is your life worth?"