Bathymetry
In the past few weeks I’ve made some useful updates to the Ice Atlas. One that’s already been helpful to me out on the ice is the addition of bathymetric contours, also known as isobaths.
These are much like the contour lines we’re used to on topographic maps, except that instead of showing how far the land is above mean sea level, they show how far below the water the land is. So the reference point is always the nominal water level of the body of water you’re looking at.
The atlas now shows isobaths for all significant bodies of water in New Hampshire, but only for a small fraction of the water in Vermont. Even though the two states have comparable numbers of lakes and ponds (about 1,000 in New Hampshire and about 800 in Vermont), most of those in Vermont either haven’t been surveyed or haven’t had their survey data converted to modern digital formats. (Meaning they’re only available as hand drawn sketches.)
If anyone knows of any data sources I might have missed, please let me know!
In addition to the discrepancy between the states, there’s also a fair bit of variation from body of water to body of water. Some are mapped at 20’ intervals, some at 5’ intervals, and some (Lake Champlain, notably) are just huge arrays of sounding depths that I had to convert into contours.
If you’re interested in the technical aspects of all this, I’ve open sourced the work I did to get the Vermont data usable: github.com/cboone/vermont-lakes-and-ponds-bathymetry
On the ice
I was skating on Smith Pond the other day. The ice was generally quite good, but there were some thin sections, so I was testing as I went. I pulled out my phone, pulled up the Smith Pond entry in the atlas, made the map full-screen , tapped the “you are here” button , and I was able to see the depth of the pond while I was on the ice. Super cool!
— Christopher Boone