Look up ground elevation at up to 100 coordinates in one call, in meters and feet, with the dataset and resolution behind every point. Inside USGS 3DEP coverage (the US and its territories, plus much of Canada and Mexico) values come from 3DEP at 1–30 m resolution. Elsewhere they come from Open Topo Data: SRTM at about 30 m on land between 60°N and 56°S, and Mapzen terrain tiles beyond SRTM's coverage and over the ocean, where values below 0 m are sea-floor depths. A point with no data in any queried dataset returns status no_data instead of failing the call.
Sample terrain elevation at evenly spaced points along a route (a polyline of 2–1,000 vertices) and summarize it. Returns total distance, cumulative ascent and descent, start, end, minimum, and maximum elevation, and the steepest climb and descent grades, plus the per-sample profile with each sample's dataset unless include_samples is false. Ascent and descent are summed between samples, so they depend on the sample spacing reported in the result: denser sampling captures more small climbs, down to the source's resolution. Over open water, Mapzen samples are sea-floor depths. Each USGS 3DEP sample is a separate upstream request, so up to 250 samples take roughly 10–30 seconds.
Sample a regular grid of terrain elevations across a bounding box and report the highest and lowest sampled points, the mean elevation, and the relief, plus the full elevation matrix with each cell's dataset. Values are point samples at grid nodes (box edges included), not cell averages, so a summit between nodes is missed; to refine a candidate high or low point, call again with a smaller box around it. Over open water, Mapzen cells are sea-floor depths. Rows times columns may not exceed 250.
Check whether terrain blocks the straight sightline between an observer and a target, each at a height above the ground, accounting for earth curvature and atmospheric refraction. Returns a verdict of clear, blocked, or indeterminate (when samples along the line have no data), the minimum clearance and the terrain point that limits it, and the first obstruction from the observer when blocked. With frequency_mhz, it also reports first Fresnel zone clearance against the 60% free-space bar. Where Mapzen reports sea-floor depth over open water, clearance is measured to the sea surface; USGS 3DEP values below 0 m (bay floor in some bays, or dry land) count as received unless water_surface_m sets a water level. Models terrain only: buildings and vegetation are not modeled beyond what the elevation source itself captures, and a ridge narrower than the reported sample spacing can be missed. To see the terrain between the points, call elevation_get_profile on the same two points.