Okay, I'm trying to remember this from my last trip:

Here's how I THINK I did it. Use PAGES and go to the NAVIGATION (or GPS) page. Then you will find the options either the first time you press MENU or the second time. Just play with it and you will get it. If you can't pm me and I'll go out to my boat when it's daylight (it's now 12:09 am) and I'll get you some better instructions.

I know you can't do it from the SONAR page and that was my problem. My 520 is a great little machine. I just wish it had a 7" screen for my aged eyes. lol

aj