# U.S. lake shorelines

Reviewed 7 September 2026. The shoreline is not bathymetry, a live water-level feed or a navigation chart. Ripples are decorative and do not represent measured currents. Lake metrics and water connections use the separate NOAA, USGS and NPS sources linked in each lesson.

- The five Great Lakes, Lake Tahoe and Great Salt Lake use [Natural Earth 1:10m lakes, version 5.0.0](https://www.naturalearthdata.com/downloads/10m-physical-vectors/10m-lakes/), public-domain generalized cartography. Interior island rings are preserved. Great Salt Lake changes substantially with water level; the outline is a reference shape, not today’s shore.
- Crater Lake uses © [OpenStreetMap contributors](https://www.openstreetmap.org/copyright), [relation 147401](https://www.openstreetmap.org/relation/147401), retrieved 7 September 2026 through Overpass. The basic Natural Earth shape omitted islands, so it was not used for this closer learning view. Source ways were assembled only at identical endpoints; one outer shore and eight interior island/rock rings were retained. No missing edge was invented.
- The [adapted Crater Lake GeoJSON](/maps/crater-lake-osm-adapted.geojson) is available under the [Open Database License 1.0](https://opendatacommons.org/licenses/odbl/1-0/). Geographic coordinates are retained. The rendered map projects them into Albers coordinates and rounds the display geometry to 0.01 map units.
- Broader land context uses NASA Blue Marble imagery from July 2004 and Census-based U.S. state outlines. See [terrain credits](/licenses/TERRAIN.md). Satellite colors do not identify a species or today’s conditions.

No lake-shaped column is presented as the lake floor. Comparison bars show the stated measure and unit; maximum depth and surface area are different quantities.

## Crater Lake shoreline close-up

The close-up uses **USGS/USDA NAIP aerial imagery acquired September 23, 2022**, separate from the historical NASA raster in the regional map. The [USGS NAIP service](https://imagery.nationalmap.gov/arcgis/rest/services/USGSNAIPImagery/ImageServer) describes the imagery as public domain. The requested mosaic locks 20 source raster IDs; each record has the same acquisition date. The source 0.3 m imagery was exported in natural color to the map's EPSG:3857 extent and compressed as a 1,200 × 820 WebP. This display is an overview, not a promise of 0.3 m screen resolution or current conditions. No invented landscape texture is added.

Request parameters, raster identifiers, image extent, attribution and hashes are retained in `docs/research/crater-naip-2022-source.json` and `data/crater-closeup-surface-provenance.json`. Source images and the vector shoreline have different acquisition histories; the outline is a reference shape, not a current water-level survey.

Wizard Island and Phantom Ship are independently selectable land in the close-up. The small circle for Phantom Ship enlarges its location for touch selection, not its area. The water polygon preserves all eight source island/rock holes. Their short stories cite [NPS Wizard Island](https://www.nps.gov/crla/learn/nature/wizardisland.htm) and [NPS Phantom Ship](https://www.nps.gov/places/phantom-ship-overlook.htm). No lake-floor depth is modeled.