Data & methodology
DepthScout maps 11,500+ lakes, rivers and coastal waters across 50 US states and Canadian provinces. Every depth number on this site traces to a named source, and every chart is labeled with how it was made. This page explains both.
Where the depth data comes from
- State fisheries agencies. GPS depth surveys and digitized lake maps from agencies including the Ohio DNR Division of Wildlife, Indiana DNR, Michigan DNR, Minnesota DNR, NYSDEC Lake Map Series, Texas Water Development Board, Vermont/New Hampshire/Maine fisheries departments, Montana FWP, ADF&G's Morphometric Atlas of Alaskan Lakes, and the Nova Scotia Lake Inventory.
- Federal survey programs. USGS bathymetric surveys (including reservoir surveys in Puerto Rico and South Carolina), US Army Corps of Engineers reservoir data, and NOAA hydrographic surveys (ENC soundings, referenced to low tide) for coastal bays and harbors.
- Canadian provincial programs. Québec's Géobase des bathymétries de lac (GBLQ, MELCCFP), British Columbia's FISS bathymetric and lake-survey databases, and Ontario lake survey data.
- OpenStreetMap. Real shorelines and island geometry for every water, © OpenStreetMap contributors.
The two labels, and what they promise
“Survey depth data” (10,246 waters): Contours interpolated from real measured bathymetry — government GPS soundings, digitized agency survey maps, or hydrographic surveys. The humps, channels and drop-offs you see were measured, not guessed — these waters draw solid contour lines.
“Approximated contours” (everything else): A computer-generated estimate built from the water's real shoreline and a verified maximum depth — not measured contours. Solid facts, estimated lines: that's why they're drawn dashed. The shape and location are right and the depth scale is anchored to a real, named-source figure — but individual contour lines are estimates, which is why these waters draw dashed contour lines on the map. We never claim a survey badge for modeled contours, and waters with no real depth figure at all simply don't ship.
How fishing spots are scored
A rules engine scores each piece of detected structure — points, humps, weedlines, drop-offs, creek channels, timber — against the selected species' seasonal depth range and structure preferences, drawn from published fisheries biology. Each highlighted zone shows its score and a plain-English reason. Spots are recommendations grounded in structure and season, not guarantees of fish.
Corrections and limits
Reservoir pools rise and fall, surveys age, and models are models — if you find something wrong, use the feedback button on any lake page and we'll trace it back to the source data. Nothing on DepthScout is for navigation. Depths can be wrong or out of date; always follow official charts and local regulations on the water.