4. Model settings
Uses USGS/NED 10m terrain first, then backup terrain services if the browser/network blocks the request. Cached in your browser.
What this does / limitations
This uses terrain elevation samples and an effective-Earth-radius model. It estimates line-of-sight, 60% first Fresnel-zone clearance, free-space path loss, and link margin. It does not model trees, buildings, antenna patterns, local noise, or multipath.