usgs-elevationUSGS Elevation Point Query Service (EPQS), 3D Elevation Program (3DEP), and topographic CONTOUR LINES. Get elevation at points, batch elevation queries, elevation profiles along routes, and topo contour-line vector data (GeoJSON) for rendering on a map. CRITICAL USAGE RULES: 1. No authentication required 2. Use getElevation() for single point elevation 3. Use getElevationProfile() for pipeline route terrain analysis 4. Use getContoursGeoJSON() for topographic contour LINES — requires a bbox or near (lat/lon) because contour data is dense; pass the result to patchops_addMapLayer to draw them 5. Units: 'Feet' or 'Meters' (default Feet)