# Map 42 source and license notes

## Map

**Dissolved Oxygen Explorer: Recent USGS Measurements**  
Public URL: <https://mitchellcoinc.com/maps/42-dissolved-oxygen-recent-usgs-measurements.html>

Initial publication: 2026-10-10

## Runtime source

Map 42 requests the U.S. Geological Survey modern Water Data OGC API `latest-continuous` collection after an explicit user action. Requests use parameter code `00300`, defined by USGS as dissolved oxygen in water, restrict results to stream sites (`site_type_code=ST`), and include the current map bounding box plus a rolling 48-hour observation window.

The browser sends one anonymous, keyless request per permitted load and caps responses at 500 features. A 60-second client cooldown prevents rapid repeat requests. No proxy, proprietary GIS service, credential, or saved measurement snapshot is used.

- USGS Water Data OGC API documentation: <https://api.waterdata.usgs.gov/docs/ogcapi>
- USGS latest-continuous collection: <https://api.waterdata.usgs.gov/ogcapi/v1/collections/latest-continuous?f=html>
- USGS parameter-code collection: <https://api.waterdata.usgs.gov/ogcapi/v1/collections/parameter-codes?f=html>
- USGS copyrights and credits: <https://www.usgs.gov/information-policies-and-instructions/copyrights-and-credits>

USGS-authored data and information are generally public domain in the United States. Source credit is retained, no USGS logo is used as MitchellCo identity, and no endorsement is implied.

## Basemap and renderer

- OpenStreetMap tiles and data: © OpenStreetMap contributors, Open Database License. <https://www.openstreetmap.org/copyright>
- Leaflet 1.9.4: BSD-2-Clause. <https://github.com/Leaflet/Leaflet/blob/v1.9.4/LICENSE>

## Scope and limitations

- Values are recent continuous measurements returned for the requested area and 48-hour window. They may be provisional and subject to revision.
- A point represents a monitoring location and time series, not the dissolved-oxygen condition of every part of a river, lake, watershed, or downstream reach.
- Multiple time series or sensors can exist at one site; the map preserves time-series identifiers rather than silently merging them.
- Dissolved oxygen changes with temperature, flow, depth, time of day, biological activity, sensor placement, season, and other local conditions.
- The four display colors are descriptive value bands, not ecological, species, habitat, impairment, swimming-safety, drinking-water, or regulatory thresholds.
- The 500-feature ceiling can truncate a broad view. The page tells users to zoom in when the response reaches the cap.
- The map does not infer cause, trend, ecosystem health, fish stress, fish mortality, habitat suitability, impairment, recreational safety, drinking-water safety, or regulatory compliance.
- If the runtime request fails, the page reports the feed as unavailable and does not substitute stale data.