Find USACE river mile markers near a point or within a geometry.

Accepts EITHER a lat/lon pair (+ radius_meters) OR a GeoJSON geometry string.

Use lat+lon when: "What river mile markers are near 31.45, -92.71?", "Markers within 2 km of this boat ramp?" Use geometry when: "Which markers fall inside this county polygon / bbox?", "Markers along this river-reach corridor?"

For point (lat/lon) queries, each returned marker includes 'distance_m' (great-circle meters from the query point) and results are sorted nearest-first. Geometry queries return markers intersecting the geometry.

Returns: { "count": int, # markers returned (after limit) "truncated": bool, # true if more markers matched than returned "markers": [ { name, MILE, RIVER_NAME, RIVER_CODE, RIVER_NUMB, LONGITUDE1, LATITUDE1, SOURCE, distance_m? }, ... ], "query": { "type": str, "radius_meters": float|null, "crs_epsg": int }, "provenance": { source agency, dataset, service URL, layer, CRS, retrieved_utc } }

Error responses:

• "Error: supply either lat+lon or geometry, not both (or neither)"

• "Error: 'geometry' is not valid JSON: ..."

• "Error: unsupported geometry type ..."

• "Error: River Mile request failed: ..."

Return the single closest river mile marker to a WGS84 coordinate.

Answers "what river mile am I at?" / "nearest marker to this point". Searches within max_radius_meters and returns the nearest marker with its great-circle distance, plus a plain-language finding.

Returns: { "finding": str, # e.g. "Nearest marker: RED River, Mile 111, ~180 m NE" "found": bool, "nearest": { name, MILE, RIVER_NAME, RIVER_CODE, RIVER_NUMB, LONGITUDE1, LATITUDE1, SOURCE, distance_m, bearing } | null, "candidates_searched": int, "query": { "lat": float, "lon": float, "max_radius_meters": float, "crs_epsg": int }, "provenance": { source agency, dataset, service URL, layer, CRS, retrieved_utc } }

Error responses:

• "Error: River Mile request failed: ..."

Query USACE river mile markers by river name and/or mile-value range.

Use when: "List markers on the RED river", "How many markers on the Mississippi between mile 400 and 600?", "Show markers on the Ohio above mile 900" (mile_min=900).

Results are ordered by MILE ascending and paginated. total_count reflects all matching markers; use next_offset to fetch the next page.

Returns: { "count": int, # markers on this page "total_count": int, # total markers matching the filter "has_more": bool, "next_offset": int|null, # pass as 'offset' to get the next page "where": str, # the WHERE clause applied (for transparency) "markers": [ { name, MILE, RIVER_NAME, RIVER_CODE, RIVER_NUMB, LONGITUDE1, LATITUDE1, SOURCE }, ... ], "provenance": { source agency, dataset, service URL, layer, CRS, retrieved_utc } }

Error responses:

• "Error: mile_min cannot be greater than mile_max"

• "Error: provide at least one filter (river_name, mile_min, or mile_max)"

• "Error: River Mile request failed: ..."