You need an elevation to go with that.

Sigh. Some people are never satisfied.

Anyway. I can eyeball it as about 20m, but my GPS tells me 30m; I don't know whether it's a different datum that causes it, or whether I'm being conservative in my guesses. (The USGS topo that I found shows my place as being right on the 20ft contour, so...)

You did also help me realize that I mistyped my latitude. Going back and correcting it now.