Check the Depths
Read From the State's Own Survey
Every contour on a print is a line the state's surveyors drew, and every published figure is copied as the state's page states it, with the page and the day we read it.
Last updated
Where the shoreline comes from
Each lake is drawn from OpenStreetMap, the map its volunteers survey: the water's outline and its islands, the bays and points they've named, the streams running in and out, and the roads round the shore. Your browser asks the Overpass API for it when you choose a lake. The 33 lakes in the gallery carry their own copy, read on 18 October 2026 (UTC), so their pages and their prints never shift with the map.
Where the depths come from
Three states publish their lake depth surveys as open data we can read line by line: the Minnesota DNR's lake bathymetric contours, with LakeFinder for each lake's published maximum depth and area; the Michigan DNR's Inland Lake Contours, Lake Deep Points and reference hydrography; and the Connecticut DEEP's lake bathymetry contours. When you choose a lake in one of those states, our server asks the state's service for the contours inside its shoreline. Every other state publishes depths as figures on a page, and the print sets those figures beside the shoreline with the page they came from.
How a lake is measured
The area is the water inside the shoreline less every island, measured on the WGS84 ellipsoid, the surface a GPS uses, by carrying each point to an equal-area plane. The shoreline is the length of every ring, islands of 500 square metres or more included. The longest open water is the longest straight line between two points of the shore that never crosses land or an island.
Their Depth Beside Ours
We check every gallery lake against the figures its state publishes. The deepest contour has to come within the larger of 5% and 3 ft of the published maximum, and the measured area within the larger of 5% and 20 acres of the published acreage. Both tolerances were fixed before the first comparison ran and are never loosened. A lake outside one stays in the table with its reason.
The depth, 20 surveyed lakes
| Lake | The state publishes | Deepest contour | Difference | Tolerance | Within it? |
|---|---|---|---|---|---|
| Lake Minnetonka | 113 ft Minnesota DNR LakeFinder | 100 ft | −13 ft | 5.7 ft | Outside: the DNR's deepest contour is 100 ft against LakeFinder's 113 ft, more than one 10 ft interval apart; the cause is not established |
| Gull Lake | 80 ft Minnesota DNR LakeFinder | 80 ft | +0 ft | 4.0 ft | Within |
| Whitefish Lake | 62 ft Minnesota DNR LakeFinder | 60 ft | −2 ft | 3.1 ft | Within |
| Detroit Lake | 89 ft Minnesota DNR LakeFinder | 80 ft | −9 ft | 4.5 ft | Outside: the state's maximum is one sounding and the deepest contour is a line drawn above it; the gap is inside one contour interval (9 ft under a 10 ft interval) |
| White Bear Lake | 83 ft Minnesota DNR LakeFinder | 80 ft | −3 ft | 4.2 ft | Within |
| Lake Waconia | 37 ft Minnesota DNR LakeFinder | 35 ft | −2 ft | 3.0 ft | Within |
| Lake Bemidji | 76 ft Minnesota DNR LakeFinder | 70 ft | −6 ft | 3.8 ft | Outside: the state's maximum is one sounding and the deepest contour is a line drawn above it; the gap is inside one contour interval (6 ft under a 10 ft interval) |
| Lake Minnewaska | 32 ft Minnesota DNR LakeFinder | 30 ft | −2 ft | 3.0 ft | Within |
| Torch Lake | 250 ft Michigan DNR, IFR lake deep points | 250 ft | +0 ft | 12.5 ft | Within |
| Higgins Lake | 130 ft Michigan DNR, IFR lake deep points | 130 ft | +0 ft | 6.5 ft | Within |
| Walloon Lake | 100 ft Michigan DNR, IFR lake deep points | 100 ft | +0 ft | 5.0 ft | Within |
| Lake Charlevoix | 122 ft Michigan DNR, IFR lake deep points | 122 ft | +0 ft | 6.1 ft | Within |
| Crystal Lake | 175 ft Michigan DNR, IFR lake deep points | 175 ft | +0 ft | 8.8 ft | Within |
| Big Glen Lake | 130 ft Michigan DNR, IFR lake deep points | 130 ft | +0 ft | 6.5 ft | Within |
| Elk Lake | 150 ft Michigan DNR, IFR lake deep points | 150 ft | +0 ft | 7.5 ft | Within |
| Lake Candlewood | 85 ft Candlewood Lake Authority (regional authority of the five lake towns) | 80 ft | −5 ft | 4.3 ft | Outside: the state's maximum is one sounding and the deepest contour is a line drawn above it; the gap is inside one contour interval (5 ft under a 10 ft interval) |
| Bantam Lake | 26 ft Connecticut Department of Energy and Environmental Protection (Draft Bantam Lake TMDL fact sheet) | 24 ft | −2 ft | 3.0 ft | Within |
| Lake Waramaug | 40 ft U.S. Geological Survey (WRI 95-4098, Water-quality characteristics of selected public recreational lakes and ponds in Connecticut) | 40 ft | +0 ft | 3.0 ft | Within |
| Lake Zoar | 75 ft U.S. Geological Survey (WRI 95-4098, Water-quality characteristics of selected public recreational lakes and ponds in Connecticut) | 64 ft | −11 ft | 3.8 ft | Outside: the state's maximum is one sounding and the deepest contour is a line drawn above it; the gap is inside one contour interval (11 ft under a 16 ft interval) |
| Lake Lillinonah | 100 ft U.S. Geological Survey (WRI 95-4098, Water-quality characteristics of selected public recreational lakes and ponds in Connecticut) | 80 ft | −20 ft | 5.0 ft | Outside: the state's maximum is one sounding and the deepest contour is a line drawn above it; the gap is inside one contour interval (20 ft, exactly one 20 ft interval) |
The area, 31 lakes with a published acreage
| Lake | Published | We measure | Difference | Tolerance | Within it? |
|---|---|---|---|---|---|
| Lake Minnetonka | 14,205.54 acres Minnesota DNR LakeFinder | 13,390 acres | −5.7% | 710 acres | Outside: OpenStreetMap's relation for the lake is 816 acres smaller than the DNR's figure; whether a bay is mapped as its own water body is not yet checked |
| Gull Lake | 10,009.97 acres Minnesota DNR LakeFinder | 9,921 acres | −0.9% | 500 acres | Within |
| Whitefish Lake | 709.18 acres Minnesota DNR LakeFinder | 712 acres | +0.5% | 35 acres | Within |
| Detroit Lake | 3,067.11 acres Minnesota DNR LakeFinder | 3,191 acres | +4.0% | 153 acres | Within |
| White Bear Lake | 2,427.7 acres Minnesota DNR LakeFinder | 2,430 acres | +0.1% | 121 acres | Within |
| Lake Waconia | 3,080.35 acres Minnesota DNR LakeFinder | 3,078 acres | −0.1% | 154 acres | Within |
| Lake Bemidji | 6,595.93 acres Minnesota DNR LakeFinder | 6,575 acres | −0.3% | 330 acres | Within |
| Lake Minnewaska | 8,050.27 acres Minnesota DNR LakeFinder | 8,011 acres | −0.5% | 403 acres | Within |
| Torch Lake | 18,713.5 acres Michigan DNR reference hydrography | 18,800 acres | +0.5% | 936 acres | Within |
| Higgins Lake | 10,187.14 acres Michigan DNR reference hydrography | 10,221 acres | +0.3% | 509 acres | Within |
| Walloon Lake | 4,576.78 acres Michigan DNR reference hydrography | 4,608 acres | +0.7% | 229 acres | Within |
| Lake Charlevoix | 17,255.86 acres Michigan DNR reference hydrography | 17,214 acres | −0.2% | 863 acres | Within |
| Crystal Lake | 9,864.69 acres Michigan DNR reference hydrography | 9,891 acres | +0.3% | 493 acres | Within |
| Lake Candlewood | 5,064 acres Connecticut Department of Energy and Environmental Protection (Freshwater Fishing Guide, Lake and Pond Regulations) | 5,252 acres | +3.7% | 253 acres | Within |
| Bantam Lake | 947 acres Connecticut Department of Energy and Environmental Protection (Freshwater Fishing Guide, Lake and Pond Regulations) | 967 acres | +2.1% | 47 acres | Within |
| Lake Waramaug | 656 acres Connecticut Department of Energy and Environmental Protection (Freshwater Fishing Guide, Lake and Pond Regulations) | 665 acres | +1.3% | 33 acres | Within |
| Lake Zoar | 909 acres Connecticut Department of Energy and Environmental Protection (Freshwater Fishing Guide, Lake and Pond Regulations) | 962 acres | +5.8% | 45 acres | Outside: a reservoir: the published acreage is the agency's figure at its stated pool and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood; which level is not established (53 acres over) |
| Lake Lillinonah | 1,547 acres Connecticut Department of Energy and Environmental Protection (Freshwater Fishing Guide, Lake and Pond Regulations) | 1,597 acres | +3.2% | 77 acres | Within |
| Geneva Lake | 5,401 acres Wisconsin Department of Natural Resources (Lake Pages, WBIC 758300) | 5,420 acres | +0.3% | 270 acres | Within |
| Lake Winnipesaukee | 44,586 acres New Hampshire Office of Planning and Development (Public Access Maps; source NH GRANIT) | 44,496 acres | −0.2% | 2,229 acres | Within |
| Lake George | 28,451 acres New York State Department of Environmental Conservation | 28,482 acres | +0.1% | 1,423 acres | Within |
| Coeur d'Alene Lake | 32,000 acres Idaho Department of Environmental Quality and the Coeur d'Alene Tribe (Coeur d'Alene Lake Management Plan, March 2009) | 27,726 acres | −13.4% | 1,600 acres | Outside: the published 32,000 acres is a round figure from the 2009 management plan, 13 percent above our shoreline; what it counts is not established |
| Lake of the Ozarks | 54,000 acres Missouri Department of Natural Resources (PUB3083) | 52,297 acres | −3.2% | 2,700 acres | Within |
| Lake Lanier | 38,000 acres Georgia Department of Natural Resources, Wildlife Resources Division | 38,316 acres | +0.8% | 1,900 acres | Within |
| Lake Travis | 18,622 acres Texas Parks and Wildlife Department | 17,588 acres | −5.6% | 931 acres | Outside: a reservoir: the published acreage is the agency's figure at its stated pool and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood; which level is not established (5.6 percent under) |
| Lake Chelan | 32,980 acres Washington State Department of Ecology (Lake Chelan Watershed DDT and PCB Total Maximum Daily Load, pub. 06-10-022) | 32,691 acres | −0.9% | 1,649 acres | Within |
| Flathead Lake | 122,885.03 acres Montana Fish, Wildlife & Parks (FishMT waterbody details) | 123,250 acres | +0.3% | 6,144 acres | Within |
| Lake Martin | 39,180 acres Alabama Department of Conservation and Natural Resources (Outdoor Alabama) | 34,609 acres | −11.7% | 1,959 acres | Outside: a reservoir: the published acreage is the agency's figure at its stated pool and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood; which level is not established (11.7 percent under) |
| Lake Oconee | 19,050 acres Georgia Department of Natural Resources, Wildlife Resources Division | 17,441 acres | −8.4% | 953 acres | Outside: a reservoir: the published acreage is the agency's figure at its stated pool and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood; which level is not established (8.4 percent under) |
| Lake Keowee | 18,372 acres South Carolina Department of Natural Resources | 17,012 acres | −7.4% | 919 acres | Outside: a reservoir: the published acreage is the agency's figure at its stated pool and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood; which level is not established (7.4 percent under) |
| Lake Murray | 48,579 acres South Carolina Department of Natural Resources | 48,564 acres | −0.0% | 2,429 acres | Within |
Why our depth reads shallower
The state's maximum depth is one sounding, taken at the very bottom of the deep hole. Its contours are lines drawn at a fixed interval, often every 10 ft, and the deepest one sits above that sounding by anything up to one interval. We print the contour and never draw a line below the last one the surveyors drew, so on most lakes our figure is the smaller of the two, and the sheet labels both.
Why an area can differ
Most of the misses in the area table are reservoirs. The published acreage is the dam operator's figure at full pool, and the OpenStreetMap shoreline was traced from imagery at whatever level the water stood that day. Lake Minnetonka is the one natural lake outside tolerance: the map's outline is 816 acres smaller than the DNR's figure, and whether a bay is mapped as a lake of its own isn't checked yet.
How each style is drawn
Every style is drawn from the same shoreline and the same survey; what changes is what the drawing keeps.
- Bathymetric
- Each closed contour of the state's survey filled a shade deeper than the one round it, inside the shoreline.
- Chart
- Pale water with the shallows tinted above the second contour, each contour labelled with its depth in feet.
- Contour
- The survey's depth contours in the water, every fifth heavier, and the ground's own contours on the land.
- Survey
- The shoreline and every contour in one ink, nothing filled.
- Linocut
- The water printed as one solid block and each contour cut out of it in the paper's colour.
- Gilt
- The shoreline and the contours in gold on black or navy, with a gold keyline round the sheet.
- Watercolour
- Two washes deepening with the depth, and a cool shadow on every north-facing bank, read from the ground's aspect.
- Relief
- The hills round the lake in the shadows cast by a low sun from the north-west.
- Oblique
- The lake seen from the far shore, 60 degrees down, the ground round it drawn at twice its height.
How a pin tone is offered
A tone is offered on a ground only where your pin holds 3:1 contrast against it, the floor for a mark you need to find, and the pin's name is set in the tone only where it holds 4.5:1; otherwise the name is set in the sheet's ink. On the darkest grounds that leaves fewer than eight tones, and the styles page shows which.
What we refuse
- A depth the state didn't survey. A lake without an open survey prints its shoreline and says so.
- A fishing spot. The print carries the lake's contours and its deep hole, and nothing marks where a fish holds.
- A figure the browser sends. The server reads the survey again and measures the lake before it prints.